Reviewer in HAPP111 (Finals) c.

Heart Layers

Lesson 1: Cardiovascular System (1)

The Cardiovascular System

 A closed system of the heart and blood
vessels
 The heart pumps blood
 Blood vessels allow blood to circulate
to all parts of the body
 The function of the cardiovascular system is
to deliver oxygen and nutrients and to
remove carbon dioxide and other waste
products

A. Functions

1. Regulates blood supply

2. Generates blood pressure
3. Route's blood
4. Ensures 1-way blood flow

B. Structures

a. Heart Characteristic

Location
 between lungs in thoracic cavity

Orientation
 apex (bottom) towards left side

d. Cardiac Muscle

 Striated (actin and myosin)

 Ca2+ and ATP used for contractions
 Intercalated disks connect cells

b. Heart Coverings

e. Chambers and Blood Vessels

 There are four hambers

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 g. Ventricles
 Lower portion; Pumping chambers
 Thick, strong walled, contract forcefully to
propel blood out of heart

Interventricular Septum
 separates right and left ventricles

Right Side of Heart: Pulmonary Circuit

 carries blood from heart to lungs
 blood is O2 poor, CO2 rich

1. Right Atrium
 receives blood from 3 places: superior and
inferior vena cava and coronary Sinus

Tricuspid Valve
 The passage before the right ventricle

2. Right Ventricle
 opens into pulmonary trunk

Pulmonary Trunk
 splits into right and left pulmonary arteries

Pulmonary Valve
 The passage before the pulmonary arteries

3. Pulmonary arteries
 carry blood away from heart to lungs

Left Side Of Heart: Systemic Circuit

 carries blood from heart to body
 blood is O2 rich, CO2 poor

1. Left Atrium
f. Atria  4 openings (pulmonary veins) that receive
 Upper portion; Holding chambers blood from lungs
 Small, thin walled, contract minimally to
push blood into ventricles Bicuspid Valve
 The passage before the left ventricle
Interatrial septum
 separates right and left atria

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2. Left Ventricle iii. Coronary Sinus
 opens into aorta  drains blood from myocardium
 thicker, contracts more forcefully, higher
blood pressure than right ventricle has to get 2. Right Ventricle
to body  opens into pulmonary trunk

Aortic Valve i. Pulmonary Trunk

 The passage before the aorta splits into right and left pulmonary arteries

3. Aorta Pulmonary Arteries

 carries blood from Left Ventricle to body  carry blood away from heart to lungs

C. Circuits of the Heart b. Systemic Circuit

Left Side Of Heart: Systemic Circuit

 carries blood from heart to body
 blood is O2 rich, CO2 poor

1. Left Atrium
 4 openings (pulmonary veins) that receive
blood from lungs

2. Left Ventricle
 opens into aorta
 thicker, contracts more forcefully, higher
blood pressure than right ventricle has to get
to body

3. Aorta
 carries blood from Left Ventricle to body

a. Pulmonary Circuit

Right Side Of Heart: Pulmonary Circuit

 carries blood from heart to lungs
 blood is O2 poor, CO2 rich D. Blood Flow
1. Right Atrium
 receives blood from 3 places: superior and
inferior vena cava and coronary sinus

i. Superior Vena Cava

 drains blood above diaphragm (head, neck,
thorax, upper limbs)

ii. Inferior Vena Cava

 drains blood below diaphragm
(abdominopelvic cavity and lower limbs)

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 G. Cardiac Cycle
 Heart is 2 side by side pumps: right and left
 Atria: primers for pumps Ventricles: power
pumps
 Cardiac Cycle: repetitive pumping action
which includes contraction and relaxation
 Cardiac muscle contractions produce
pressure changes within heart chambers.
 Pressure changes are responsible for blood
movement.
 Blood moves from areas of high to low
pressure.

H. Heart Sounds

Stethoscope
 is used to hear lung and heart sounds

 First sound is lubb, second is dupp

 Sounds result from opening and closing
valves
 Murmurs are due to faulty valves

E. Blood Supply

Coronary Arteries
 supply blood to heart wall
 originate from base of aorta (above aortic
semilunar valve)  Structures from the blood flow create
audible sounds — the more turbulent the
a. Left Coronary Artery blood flow, the more vibrations that get
 has 3 branches created.
 supply blood to anterior heart wall and left
ventricle I. Regulation Of Heart Function

b. Right Coronary Artery Stroke Volume

 originates on right side of aorta  volume of blood pumped per ventricle per
 supply blood to right ventricle contraction
 70 ml/beat
F. Action Potential In Cardiac Muscle
 Changes in membrane channels’ Heart Rate
permeability are responsible for producing  number of heart beats in 1 min.
action potentials and is called pacemaker  72 beats/min.
potential.

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Cardiac Output 3. Physical Factors
 volume of blood pumped by a ventricle in 1  Age, gender, exercise, body temperature
min. influence heart rate
 Cardiac output is the product of the heart
rate (HR) and the stroke volume (SV) Lesson 1: Cardiovascular System (2)
 CO = HR × SV
 CO = HR (75 beats/min) × SV (70 ml/beat) Location of the Heart
 CO = 5250 ml/min = 5.25 L/min  In the mediastinum between second rib and
 CO = HR x SV fifth intercostal space; on superior surface of
 5250 ml/min = 75 beats/min x 70 mls/beat diaphragm; two thirds to the Left of the
 Norm = 5000 ml/min midsternal line; anterior to vertebral column,
 Entire blood supply passes through body posterior to sternum.
once per minute.  About the size of your fist less than 1lb.
 CO varies with demands of the body.
The Heart: Coverings

Pericardium
 a double serous membrane

Parietal Layer
 next to heart

Visceral Layer
 outside layer

Serous Fluid
 fills the space between the layers of
pericardium.

Parietal Layer Of Pericardium

 Clear fibrous bag protecting and anchoring
heart. Limits filling beyond a certain volume.

Visceral Layer
 On external surface of heart; very thin layer
of fluid between layers to decrease friction.

Endocardium
 the thin layer of the heart wall. This layer
lines the inner heart chambers, covers heart
valves, and is continuous with the
endothelium of large blood vessels. The
endocardium of heart atria consists of
smooth muscle, as well as elastic fibers.
Factors Modifying Basic Heart Rate
Heart
1. Neural (ANS) Controls  The heart is a four-chambered, hollow,
 Sympathetic nervous system speeds heart muscular organ that is slightly larger than a
rate man’s closed fist. It is surrounded by a thin
 Parasympathetic nervous system, primarily fluid-filled sac called the pericardium, and its
vagus nerve fibers, slow and steady the heart walls have three distinct layers.
rate  The heart has two sides, a right and a left.
Each side has two chambers, an upper and a
2. Hormones and Ions lower. One-way valves between the
 Epinephrine and thyroxine speed heart rate chambers help prevent the backflow of
 Excess or lack of calcium, sodium, and blood and keep it moving through the heart
potassium ions also modify heart activity in the right direction.

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 The right and the left chambers are Chambers of the Heart
separated from each other by partitions  The upper chambers on each side of the
called septa (singular septum). heart are called atria, and the lower
chambers are called ventricle. The atria are
Three Layers of Heart receiving chambers, and the ventricles are
pumping or delivering chambers.
1. Epicardium (Visceral Layer)
 the thin outer layer of the heart wall. It is Two Atria
also known as visceral pericardium as it  Separated by interatrial septum; coronary
forms the inner layer of the pericardium. sulcus encircles junction of atria and
The epicardium is composed primarily of ventricles; auricles increase atrial volume.
loose connective tissue, including elastic
fibers and adipose tissue Two Ventricles
 Function: to protect the inner heart layers  Separated by interventricular septum;
and also assists in the production of anterior and posterior interventricular sulci
pericardial fluid. This fluid fills the on external surface suggest location of
pericardial cavity and helps to reduce septum inside.
friction between pericardial membranes.
Chambers of
Location Function
2. Myocardium (Muscle Of Heart) the Heart
 the middle layer of the heart wall. It is Right atrium Upper right Receives
composed of cardiac muscle fibers, which chamber deoxygenated
blood from the
enable heart contractions. The myocardium
body via both
is the thickest layer of the heart wall, with its the Superior
thickness varying in different parts of the (upper) vena
heart. The myocardium of the left ventricle cava and
is the thickest as this ventricle is responsible inferior (lower)
for generating the power needed to pump vena cava and
oxygenated blood from the heart to the rest pumps into the
of the body. right ventricle
Right Lower right Receives blood
3. Endocardium (Inner Lining) ventricle chamber from the right
atrium and
 the thin inner layer of heart wall. This layer
pumps it into
lines the inner heart chambers, covers heart the pulmonary
valves, and is continuous with the artery, which
endothelium of large blood vessels. The carries it to the
endocardium of heart atria consists of lungs to be
smooth muscle, as well as elastic fibers. oxygenated.
Left atrium Upper left chamber Receives
Layers of Location Description Function oxygenated
the Heart blood from the
Epicardium Outer Thin, Covers the lungs via the
layer of serous(watery) heart and pulmonary
the membrane attaches to veins and
heart that is the pumps it into
continuous pericardium the left
with the lining ventricle.
of the Left ventricle Lower left chamber Receives blood
pericardium from the left
Myocardium Middle Thick layer of Contracts atrium and
layer of cardiac muscle to pump pumps it into
the blood into the aorta. The
heart the arteries cell walls of the
Endocardium Inner Thin layer of Lines the left ventricle are
layer of epithelial cells interior nearly three
the that is chambers times as thick as
heart continuous and valves those of the
with the lining right ventricle
of the blood owing to the
vessels force required

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 to pump the Coronary Circulation
blood into the  Bloods in the heart chambers does not
arterial system. nourish the myocardium
 The heart has its own nourishing circulatory
Valves system
 The valves at the entrance to the ventricles  coronary arteries
are called atrioventricular (AV) valves. The  cardiac veins
valves that exit the ventricles are called  blood empties into the right atrium via the
semilunar valves because they are coronary sinus
crescent-shaped like a half moon.
 Valves open as blood is pumped through. Cardiac Pathology
 Held in place by chordae tendineae “heart
string” Rapid Heartbeat
 Close to prevent backflow  Inadequate blood
 Angina Pectoris
Valve Pathology
 Incompetent valve = backflow and Conduction System
re-pump.
 Stenosis= stiff= heart workload increased Intrinsic Conduction System (Nodal System)
 May be replaced  heart muscle cells contract, without nerve
 Lup dub heart sound impulses, in a regular, continuous way
 Special tissue sets the pace
Valves Location Description Function
Right AV Between Has three Closes when the
valve or the right cusps hence right vent. Contracts
Sinoatrial Node ( Right Atrium)
tricuspid atrium the name and prevents blood  pacemaker
valve and right tricuspid from flowing back
ventricle into the right atrium  atrioventricular node (junction of right and
Left valve Between Has two Closes when the left
or the left cusps, hence vent. Contracts and
left atria and ventricles)
Bicuspid atrium the name prevents blood  atrioventricular bundle (bundle of his)
or mitral and left bicuspid from flowing back  bundle branches (right and left)
valve ventricle into the left atrium
Cardiac Cycle
Right Ate the Has three Closes when the
semilunar entrance half-moon-s right vent. Relaxes  Atria contract simultaneously
valve or to the haped cusps and prevents blood  Atria relax, then ventricles contract
pulmonic pulmona from flowing back  Systole= contraction
/pulmona ry artery into the right
 Diastole= relaxation
ry valve ventricle
Left At the Has three Closes when the left
semilunar entrance half shaped ventricle relaxes and Regulation of Heart
valve or to the cusps prevents blood  Stroke volume usually remains relatively
aortic aorta from flowing back constant
valve into the left
ventricle  starling’s law of the heart - the more that the
cardiac muscle is stretched, the stronger the
The Heart: Associated Great Vessels contraction.
 Changing heart rate is the most common
Aorta way to change cardiac output
 leaves left ventricles
Regulation of Heart Rate
Pulmonary Arteries
 leaves right ventricles Increased Heart Rate
 sympathetic nervous system
Vena Cava  crisis
 enters right atrium  low blood pressure
 Hormones
Pulmonary Veins  epinephrine
 enter left atrium  thyroxine
 Exercise
 Decreased blood volume

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Decreased heart rate exchange of nutrients and wastes in tissues.
 Parasympathetic nervous system They also play an important role in
 High blood pressure or blood volume adjusting the velocity and volume of blood
 decreased venous return flow. Blood circulates inside the blood
 In Congestive Heart Failure the heart is vessels, which form a closed transport
worn out and pumps weakly. Digitalis system, the so-called vascular system.
works to provide a slow, steady, but
stronger beat. Five Main Types of Blood Vessels

Congestive Heart Failure (CHF) 1. Arteries carry blood away from the heart to
 Decline in pumping efficiency of heart other organs.
 Inadequate circulation 2. Arterioles are products of smaller
 Progressive, also coronary atherosclerosis, medium-sized arteries. As the arterioles enter a
high blood pressure and history of multiple tissue, they branch into numerous tiny vessels
Myocardial Infarctions called…
 Left side fails = pulmonary congestion and 3. Capillaries numerous tiny vessels branched on
suffocation the arterioles. The thin walls of capillaries allow
 Right side fails = peripheral congestion and the exchange of substances between the blood
edema and body tissues.
4. Venules small veins formed from group of
Electrocardiograms (EKG/ECG) capillaries within a tissue.
 Three formations: 5. Veins larger blood vessels that convey blood
 P wave: impulse across atria from the tissues back to the heart.
 QRS complex: spread of impulse down
septum, around ventricles in Purkinje Basic Structure of a Blood Vessel
fibers  The wall of a blood vessel consists of three
 T wave: end of electrical activity in layers, or tunics, of different tissues: an
ventricles epithelial inner lining, a middle layer
consisting of smooth muscle and elastic
connective tissue, and a connective tissue
outer covering. The three structural layers
of a generalized blood vessel from
innermost to outermost are the;

1. Tunica interna (intima)

2. Tunica media
3. Tunica externa (adventia)

Blood Vessels: Structure

1. Tunica Interna (Intima) (Tunic Garment Or

Coat; Interna Or Intima Innermost)
 forms the inner lining of a blood vessel and
is in direct contact with the blood as it flows
through the lumen.

Lumen
 interior opening of the vessel.

Endothelium
Blood Vessel  innermost layer a thin layer of flattened cells
 a tubular structure carrying blood through that lines the inner surface of the entire
the tissues and organs; a vein, artery, or cardiovascular system (heart and blood
capillary. vessels).
 Blood vessels contribute to homeostasis by
providing the structures for the flow of
blood to and from the heart and the

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Basement Membrane
 second component of tunica interna. It
provides a physical support base for the
epithelial layer and anchors the endothelium
to the underlying connective tissue while
also regulating molecular movement.

Internal Elastic Lamina (Lamina Thin Plate)

 the outermost part of the tunica interna,
which forms the boundary between the
tunica interna and tunica media, it is a thin
sheet of elastic fibers with a variable number
of window-like openings that give it the
look of Swiss cheese.

2. Tunica Media Blood Vessels: Arteries

 The tunica media (media middle) is a
muscular and connective tissue layer that Arteries
displays the greatest variation among the  The wall of an artery has the three layers of
different vessel types. The tunica media is a typical blood vessel, but has a thick
the most variable of the tunics. muscular-to-elastic tunica media. Due to
 The primary role of the smooth muscle cells, their plentiful elastic fibers, arteries normally
which extend circularly around the lumen have high compliance, which means that
like a ring encircles your finger, is to regulate their walls stretch easily or expand without
the diameter of the lumen. An increase in tearing in response to a small increase in
sympathetic stimulation typically stimulates pressure.
the smooth muscle to contract, squeezing  Elastic arteries are the largest arteries in the
the vessel wall and narrowing the lumen. body, ranging from the garden hose–sized
 Such a decrease in the diameter of the lumen aorta and pulmonary trunk to the
of a blood vessel is called vasoconstriction. finger-sized branches of the aorta. These
The resulting increase in lumen diameter is vessels are characterized by well-defined
called vasodilation. internal and external elastic laminae, along
with a thick tunica media that is dominated
3. Tunica Externa by elastic fibers, called the elastic lamellae.
 Tunica externa (externa outermost), the  Muscular arteries are medium-sized arteries
outer covering of a blood vessel, consists of because their tunica media contains more
elastic and collagen fibers. The tunica smooth muscle and fewer elastic fibers than
externa contains numerous nerves and, elastic arteries. Because the muscular
especially in larger vessels. arteries continue to branch and ultimately
 Vasa vasorum (vessels to the vessels) small distribute blood to each of the various
vessels that supply blood to the tissues of the organs, they are called distributing arteries.
vessel. They are easily seen on large vessels Examples include the brachial artery in the
such as the aorta. arm and radial artery in the forearm
 In addition to the important role of
supplying the vessel wall with nerves and
self-vessels, the tunica externa helps anchor
the vessels to surrounding tissues.

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 and form the U-turns that connect the
arterial outflow to the venous return.
 The primary function of capillaries is the
exchange of substances between the blood
and interstitial fluid. Because of this, these
thin-walled vessels are referred to as
exchange vessels.
 The flow of blood from a metarteriole
through capillaries and into a postcapillary
venule (venule that receives blood from a
capillary) is called the micro- circulation
(micro small) of the body.

The body contains three different types of

capillaries:

1. Continuous Capillaries
 Most capillaries belong to this type, in which
the plasma membranes of endothelial cells
form a continuous tube that is interrupted
only by intercellular clefts, gaps between
neighboring endothelial cells. They are
found in the central nervous system, lungs,
Anastomoses skin, muscle tissue, and the skin.
 Most tissues of the body receive blood from
more than one artery. The union of the 2. Fenestrated Capillaries
branches of two or more arteries supplying  The plasma membranes of the endothelial
the same body region is called an cells in these capillaries have many
anastomosis. Anastomoses may also occur fenestrations, small pores (holes) ranging
between veins and between arterioles and from 70 to 100 nm in diameter They are
venules. found in the kidneys, villi of the small
 The alternative route of blood flow to a intestine, choroid plexuses of the ventricles
body part through an anastomosis is known in the brain, ciliary processes of the eyes,
as collateral circulation. and most endocrine glands.
 Arteries that do not anastomose are known
as end arteries. 3. Sinusoids
 are wider and more winding than other
Blood Vessels: Arterioles capillaries.
Arterioles
 Literally meaning small arteries, arterioles
are abundant microscopic vessels that
regulate the flow of blood into the capillary
networks of the body’s tissues. The terminal
end of the arteriole, the region called the
metarteriole.
 Arterioles play a key role in regulating blood
flow from arteries into capillaries by
regulating resistance, the opposition to
blood flow. Because of this they are known
as resistance vessels.

Blood Vessels: Capillaries

Capillaries
 Capillaries (capillus little hair), the smallest
of blood vessels, have diameters of 5–10 m,

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 travel between the skeletal muscles. These
connections allow communication between
the deep and superficial flow of blood.

Blood Vessels: Venules

Venules
 Unlike their thick-walled arterial
counterparts, venules ( little vein) and veins
have thin walls that do not readily maintain
their shape. Venules drain the capillary
blood and begin the return flow of blood
back toward the heart.
 Postcapillary Venules - venules that initially
receive blood from capillaries. They are the
smallest venules and function as significant
sites of exchange of nutrients and wastes and
white blood cell emigration.
 As the postcapillary venules move away
from capillaries, they acquire one or two
layers of circularly arranged smooth muscle
cells. These muscular venules have thicker
walls across which exchanges with the
interstitial fluid can no longer occur.

Blood Vessels: Vein

 Veins lack the internal or external elastic
laminae found in arteries. They are
distensible enough to adapt to variations in
the volume and pressure of blood passing
through them, but are not designed to
withstand high pressure. The lumen of a
vein is larger than that of a comparable
artery, and veins often appear collapsed Capillary Exchange
(flattened) when sectioned.  the movement of substances between blood
 Vascular (venous) sinus is a vein with a thin and interstitial fluid.
endothelial wall that has no smooth muscle
to alter its diameter. Diffusion
 Some veins are paired and accompany  most important method of capillary
medium- to small-sized muscular arteries. exchange. Many substances, such as oxygen
These double sets of veins escort the arteries (O), carbon dioxide (CO2), glucose, amino
and connect with one another via venous acids, and hormones, enter and leave
channels called anastomotic veins. capillaries by simple diffusion.
 The subcutaneous layer deep to the skin is
another source of veins. These veins, called Transcytosis
superficial veins, course through the  A small quantity of material crosses capillary
subcutaneous layer unaccompanied by walls.This method of transport is important
parallel arteries. Along their course, the mainly for large, lipid-insoluble molecules
superficial veins form small connections that cannot cross capillary walls in any other
(anastomoses) with the deep veins that way.

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Bulk Flow: Filtration and Reabsorption 2. Blood Viscosity
 The viscosity of blood depends mostly on
Bulk Flow the ratio of red blood cells to plasma (fluid)
 passive process in which large numbers of volume, and to a smaller extent on the
ions, molecules, or particles in a fluid move concentration of proteins in plasma.The
together in the same direction. higher the blood’s viscosity, the higher the
resistance.
Filtration
 Pressure-driven movement of fluid and 3. Total Blood Vessel Length
solutes from blood capillaries into interstitial  Resistance to blood flow through a vessel is
fluid directly proportional to the length of the
blood vessel. The longer a blood vessel, the
Reabsorption greater the resistance.
 Pressure-driven movement from interstitial
fluid into blood capillaries Systemic Vascular Resistance (SVR)
 also known as total peripheral resistance
Hemodynamics: Factors Affecting Blood Flow (TPR) refers to all of the vascular resistances
offered by systemic blood vessels.
Blood Flow
 is the volume of blood that flows through Pulmonary Vascular Resistance (PVR)
any tissue in a given time period (in  vascular resistances offered by pulmonary
mL/min). blood vessels.

Blood Pressure Venous Return

 the hydrostatic pressure exerted by blood  the volume of blood flowing back to the
on the walls of a blood vessel. BP is heart through the systemic veins, occurs due
determined by cardiac output ,blood to the pressure generated by contractions of
volume, and vascular resistance the heart’s left ventricle.

Systolic Blood Pressure (SBP) Velocity of Blood Flow

 is the highest pressure attained in arteries  blood flow is the volume of blood that
during systole. flows through any tissue in a given time
period (in mL/min). The speed or velocity of
Diastolic Blood Pressure (DBP) blood flow (in cm/sec) is inversely related to
 is the lowest arterial pressure during the cross-sectional area. Velocity is slowest
diastole. where the total cross-sectional area is
greatest
Mean Arterial Pressure (MAP)
 the average blood pressure in arteries, is Circulation Time
roughly one-third of the way between the  is the time required for a drop of blood to
diastolic and systolic pressures. pass from the right atrium, through the
pulmonary circulation, back to the left
Vascular Resistance atrium, through the systemic circulation
 is the opposition to blood flow due to down to the foot, and back again to the
friction between blood and the walls of right atrium.
blood vessels.
Checking Circulation
Vascular resistance depends on:
(1) size of the blood vessel lumen, Pulse
(2) blood viscosity  The alternate expansion and recoil of elastic
(3) total blood vessel length arteries after each systole of the left ventricle
creates a traveling pressure wave.
1. Size Of The Lumen  The pulse rate normally is the same as the
 The smaller the lumen of a blood vessel, heart rate, about 70 to 80 beats per minute
the greater its resistance to blood flow. at rest.

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Tachycardia Homeostatic Responses to Shock
 is a rapid resting heart or pulse rate over 100
beats/min. Activation Of The
Renin–Angiotensin–Aldosterone System
Bradycardia  Decreased blood flow to the kidneys causes
 is a slow resting heart or pulse rate under 50 the kidneys to secrete renin and initiates the
beats/min. Endurance-trained athletes renin–angiotensin–aldosterone system
normally exhibit bradycardia.
Secretion Of Antidiuretic Hormone
Measuring Blood Pressure  In response to decreased blood pressure, the
posterior pituitary releases more antidiuretic
Blood Pressure hormone (ADH)
 usually refers to the pressure in arteries
generated by the left ventricle during systole Activation Of The Sympathetic Division Of The
and the pressure remaining in the arteries ANS
when the ventricle is in diastole.  As blood pressure decreases, aortic and
carotid baroreceptors initiate powerful
Sphygmomanometer sympathetic responses throughout the body.
 device used to measure blood pressure
Release Of Local Vasodilators
Systolic Blood Pressure (SBP)  In response to hypoxia, cells liberate
 the force of blood pressure on arterial walls vasodilators—including K, H, lactic acid,
just after ventricular contraction. adenosine, and nitric oxide—that dilate
arterioles and relax precapillary sphincters.
Diastolic Blood Pressure (DBP)
 force exerted by the blood remaining in Circulatory Routes
arteries during ventricular relaxation.
 There are two basic postnatal (after birth)
Korotkoff Sounds routes for blood flow;
 various sounds that are heard while taking
blood pressure . 1. Pulmonary Circulation
 when blood returns to the heart from the
Pulse Pressure systemic route, it is pumped out of the right
 difference between systolic and diastolic ventricle through the pulmonary circulation
pressure. to the lungs.

Shock and Homeostasis 2. Systemic Circulation

 carries oxygen and nutrients to body tissues
Shock and removes carbon dioxide and other
 is a failure of the cardiovascular system to wastes and heat from the tissues.
deliver enough O2 and nutrients to meet
cellular metabolic needs. The causes of shock Pulmonary Circulation
are many and varied, but all are  The pulmonary circulation carries
characterized by inadequate blood flow to deoxygenated blood from the right ventricle
body tissues. to the air sacs (alveoli) within the lungs and
returns oxygenated blood from the air sacs
4 Types of Shock to the left atrium.

1. hypovolemic shock due to decreased blood

volume
2. cardiogenic shock due to poor heart
function
3. vascular shock due to inappropriate
Vasodilation.
4. obstructive shock due to obstruction of
blood flow.

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 through the diaphragm, where it branches
further into arteries which supply the lower
parts of the body.
 The arteries branch into smaller arteries,
arterioles, and finally capillaries.

Systemic Circulation
 The systemic circulation carries oxygen and
nutrients to body tissues and removes
carbon dioxide and other wastes and heat
from the tissues.
 All systemic arteries branch from the aorta.
Deoxygenated blood returns to the heart
through the systemic veins.
 All veins of the systemic circulation drain
into the superior vena cava, inferior vena
cava, or coronary sinus, which in turn empty
into the right atrium. The Hepatic Portal Circulation

Hepatic Portal Circulation

 carries venous blood from the
gastrointestinal organs and spleen to the
liver.

Portal Vein
 vein that carries blood from one capillary
network to another

Hepatic Portal Vein

 receives blood from capillaries of
gastrointestinal organs and the spleen and
delivers it to the sinusoids of the liver.

Superior Mesenteric Vein

 drains blood from the small intestine and
portions of the large intestine, stomach, and
pancreas through the jejunal, ileal,
ileocolic,right colic, middle colic,
pancreaticoduodenal, and right
gastro-omental Veins.

Pathway of Systemic Circulation Splenic Vein

 Oxygen-rich blood from the lungs leaves the  drains blood from the stomach, pancreas,
pulmonary circulation when it enters the left and portions of the large intestine through
atrium through the pulmonary vein. the short gastric, left gastro-omental,
 The blood is then pumped through the pancreatic, and inferiormesenteric veins.
mitral valve into the left ventricle.
 From the left ventricle, blood is pumped Inferior Mesenteric Vein
through the aortic valve and into the aorta.  which passes into the splenic vein, drains
 The aorta arches and branches into major portions of the large intestine through the
arteries to the upper body before passing

14
 superior rectal, sigmoidal, and left colic
veins.

Right And Left Gastric Veins

 which open directly into the hepatic portal
vein, drain the stomach.

Cystic Vein
 which also opens into the hepatic portal
vein, drains the gallbladder.

Hepatic Portal Vein

 the liver is receiving nutrient-rich but
deoxygenated blood.

Hepatic Artery
 the liver also receiving oxygenated blood ,a
branch of the celiac trunk.

Sinusoids
 the oxygenated blood mixes with the
deoxygenated blood. Eventually, blood
leaves the sinusoids of the liver through the
hepatic veins, which drain into the inferior Pathology of the Heart
vena cava.
Damage to AV node
 release of ventricles from control = slower
heart beat

Slower heart beat

 can lead to fibrillation

Fibrillation
 lack of blood flow to the heart

Tachycardia
 more than 100 beats/min

Bradychardia
 less than 60 beats/min

Lesson 2: Vascular System

Blood Vessels: The Vascular System

 Taking blood to the tissues and back

The Fetal Circulation  Arteries
 Fetal circulation exists only in the fetus and  Arterioles
contains special structures that allow the  Capillaries
developing fetus to exchange materials with  Venules
its mother. It differs from the postnatal (after  Veins
birth) circulation because the lungs, kidneys,
and gastrointestinal organs do not begin to
function until birth.

15
 Capillary Beds
 Capillary beds consist of two types of vessels

a. Vascular Shunt
 directly connects an arteriole to a venule

b. True Capillaries
 exchange vessels
 Oxygen and nutrients cross to cells
 Carbon dioxide and metabolic waste
products cross into blood

Blood Vessels: Anatomy

Three Layers (Tunics)

1. Tunic Intima
 Endothelium

2. Tunic Media
 Smooth muscle
 Controlled by sympathetic nervous system

3. Tunic Externa
 Mostly fibrous connective tissue

Differences Between Blood Vessel Types

 Walls of arteries are the thickest
 Lumens of veins are larger
 Skeletal muscle “milks” blood in veins
toward the heart Diffusion at Capillary Beds
 Walls of capillaries are only one cell layer
thick to allow for exchanges between blood
and tissue

Movement of Blood Through Vessels

 Most arterial blood is pumped by the heart
 Veins use the milking action of muscles to
help move blood

Vital Signs
 Arterial pulse
 Blood pressure

16
 Repiratory Rate Blood Pressure: Effects of Factors
 Body Temperature
 All indicate the efficiency of the system 1. Neural Factors
 Autonomic nervous system adjustments
Pulse (sympathetic division)
 pressure wave of blood
 Monitored at “pressure points” where pulse 2. Renal Factors
is easily palpated  Regulation by altering blood volume
 Renin – hormonal control

3. Temperature
 Heat has a vasodilation effect
 Cold has a vasoconstricting effect

4. Chemicals
 Various substances can cause increases or
decreases

5. Diet

Variations in Blood Pressure

 Human normal range is variable

 Normal
 140–110 mm Hg systolic
 80–75 mm Hg diastolic
 Hypotension
 Low systolic (below 110 mm HG)
 Often associated with illness
 Hypertension
 High systolic (above 140 mm HG)
 Can be dangerous if it is chronic
Blood Pressure
 Measurements by health professionals are Lesson 3: The Respiratory System (1)
made on the pressure in large arteries
 Systolic – pressure at the peak of ventricular Respiratory System
contraction  Open system
 Diastolic – pressure when ventricles relax
 Pressure in blood vessels decreases as the 2 Divisions Of The Respiratory System
distance away from the heart increases 1. The upper respiratory tract
2. The lower respiratory tract
Measuring Arterial Blood Pressure
Functions of Respiratory System

1. Gas exchange
2. Regulation of blood pH
3. Voice production
4. Innate Immunity
5. Ventilation
6. Olfaction

17
 also the organ for phonation or sound
production (Voice Box).
 near the larynx

Breathing

Structures: Upper Respiratory Tract

1. Nose
 Protective structures - hair, the mucus which
can trap foreign bodies and the nasal
turbinate which may warm a cool air or
cool a warm air. The larynx is made up cartilages:

a. Epiglottis
 is a large single, leaf shaped piece of
cartilage. It pulls down the glottis when we
swallow to keep food or liquid from getting
into the trachea.

b. Glottis
 is the opening of the larynx over the true
vocal cords, air coming from the lungs cause
the vocal cord to vibrate producing sounds.

2. Nasopharynx c. Thyroid (“Adam’s apple”)

 serves as passageway of air from the nose to  largest cartilage
the larynx
 near nose d. Cricoid cartilage
 is a single ring of cartilage that connects with
the tracheal rings & for airway patency

3. Oropharynx
 near ears

4. Larynx
 This is the largest cartilage of the body. It
serves not only as the passageway of air but

18
Structures: Lower Respiratory Tract 2 Layers of Serous Membranes

 Outer is the parietal pleura

 Inner is the visceral pleura.
 Between these two layers is a pleural cavity
which contains a lubricating fluid that
prevent friction as the lungs expands.

1. The Bronchi and The Bronchial Tree

2. Lungs
 located in the thoracic cavity protected by
the ribs
 The pleural membrane encloses each lung.
 Left lung: 2 lobes
 Right lung: 3 lobes (middle lobe)

Pleural Cavity
 Fluid in lungs (containing lubricating fluid)
Carbon Dioxide
Cardiac Notch  The most important chemical regulator of
 Where heart apex (base) is lodged in the left respiration in a healthy individual.
lung  Chief regulator of blood pH

Main Respiration
 Primary Bronchi  involves exchanging oxygen and carbon
dioxide between the air and a person's
Lobar blood.
 Secondary Bronchi  When brain receptors perceive too
much carbon dioxide in the blood, they
Segmental signal the body to increase ventilation.
 Tertiary bronchi  Transport of oxygen in the Cell and
exchange of gases (02 and CO2)

19
 It is controlled by the Central Nervous External Respiration
System (CNS).  when there is exchange of gasses between
 The brain stem contains the respiratory the lungs and the blood.
center which can be stimulated by
chemoreceptors, these are special cells that 3. When the oxygenated blood goes to the
detect changes in partial pressure of oxygen tissues, oxygen is delivered to the tissues and the
and carbon dioxide. carbon dioxide produced by the cells is brought
to the blood to be carried to the lungs. This is
During Inhalation called Internal Respiration.

Breathing Pattern and Respiratory Disorders

During Exhalation

1. Hiccups
 Hiccups are caused by involuntary
contractions of your diaphragm — the
muscle that separates your chest from your
abdomen and plays an important role in
breathing. This involuntary contraction
causes your vocal cords to close very briefly,
which produces the characteristic sound of a
hiccup.

Abnormal Breathing Pattern

Pattern Mechanism
Respiratory Function Apnea Absence of breathing
Eupnea Normal breathing
Ventilation Orthopnea Only able to breathe
 refers to movement of air in and out of the comfortable in upright
lungs (O2 and CO2) position (such as sitting
 Breathing in chair), unable to
breath laying down,
1. When air enters the lungs, it carries oxygen, Paroxysmal nocturnal attacks of severe
and it goes to the blood through the pulmonary dyspnea shortness of breath that
capillaries. wakes a person from
2. Perfusion refers to the flow of blood to the sleep,
lungs from the right ventricle - - pulmonary Hyperpnea Increased depth of
capillaries, oxygen from air enters the blood and breathing.
the carbon dioxide from the blood goes to the Hyperventilation Increased rate (A) or
alveoli for release into the atmosphere. depth (B), or
combination of both
Hypoventilation Decreased rate (A) or

20
 depth (B), or some
combination of both.

Respiratory Disorders

Respiratory System
 open system. It allows oxygen to enter our
body and carbon dioxide to be removed
out of the body.

1. Emphysema
 is a progressive, degenerative disease that
destroys alveolar walls. As a result, clusters
of small air sacs merge to form larger
chambers, which drastically decreases the
surface area of the respiratory membrane
and thereby reduces the volume of gases
that can be exchanged through the Lesson 3: The Respiratory System (2)
membrane.
 Alveolar walls lose some of their elasticity, Organs And Associated Structures Of The
and capillary networks associated with the Respiratory System
alveoli diminish.

2. Chronic Bronchitis
 the mucosa of the lower respiratory passages
become severely inflamed and produces
excessive mucus. The pooled mucus impairs
ventilation and gas exchange and
dramatically increases the risk of lung
infections, including pneumonias.
 Chronic bronchitis patients are sometimes
called “blue bloaters” because hypoxia
and carbon dioxide retention occur early
in the disease and cyanosis is common.
 Cyanosis = Blue Baby

3. Lung Cancer
 Ordinarily, nasal hairs, sticky mucus, and the
action of cilia do a fine job of protecting the
lungs
 from irritants, but smoking overwhelms
 During breathing, inhaled air enters the
these cleansing devices, and they
body through the nose and passes through
eventually stop functioning.
the respiratory tract to the lungs. Exhaled air
 Continuous irritation prompts the
travels from the lungs in the opposite
production of more mucus, but smoking
direction.
slows the movements of cilia that clear this
 The nasal cavity is a large, air-filled space in
mucus and depresses lung macrophages.
the skull above and behind the nose in the
 One result is a pooling of mucus in the lower
middle of the face. respiratory functions, the
respiratory tract and an increased frequency
nasal cavity also contains chemoreceptors
of pulmonary infections, including
that are needed for the sense of smell and
pneumonia and COPD. However, it is the
that contribute importantly to the sense of
irritating effects of the “cocktail” of toxic
taste.
chemicals in tobacco smoke that ultimately
 Pharynx is a tube-like structure that
lead to lung cancer
connects the nasal cavity and the back of the
mouth to other structures lower in the
throat including the larynx. The pharynx has
dual functions: both air and food (or other

21
 swallowed substances) pass through it, so it place. Remember that in external
is part of both the respiratory and the respiration, gas exchanges are being made
digestive systems. between the blood and the body exterior.
 The larynx connects the pharynx and
trachea and helps to conduct air through the 3. Respiratory Gas Transport
respiratory tract.  Oxygen and carbon dioxide must be
 The larynx is also called the voice box transported to and from the lungs and tissue
because it contains the vocal cords, which cells of the body via the bloodstream.
vibrate when air flows over them, thereby
producing sound. very important function 4. Internal Respiration
of the larynx is protecting the trachea from  At systemic capillaries, gas exchange occurs
aspirated food. between the blood and cells inside the
 The trachea, or windpipe, is the widest body.
passageway in the respiratory tract. It is
about 2.5 cm (1 in.) wide and 10-15 cm (4-6 Gas Exchange
in.) long.  This is the biochemical process in which
 There are two main bronchial tubes, oxygen diffuses out of the air and into the
or bronchi (singular, bronchus), called the blood while carbon dioxide and other waste
right and left bronchi. gases diffuse out of the blood and into the
 The bronchi carry air between the trachea air. All of the organs of the respiratory
and lungs. system are involved in breathing, but only
 The smallest bronchi branch into very small the lungs are involved in gas exchange.
tubules called bronchioles.
 The tiniest bronchioles end in alveolar ducts, Major structures associated with the respiratory
which terminate in clusters of minuscule air tract in the head and neck:
sacs, called alveoli.

During Inhalation
 Diaphragm contracts to pull downward
 Chest muscles contract to pull open the chest

During Exhalation
 Muscles relaxed
 Allows lungs to spring back to its original
size
 Pushes air out

Respiration
 is the life-sustaining process in which gases
are exchanged between the body and the
outside atmosphere.

Ventilation or Breathing
 This is the physical process of conducting air
to and from the lungs.
Breathing In
 Air flows into the nostrils and enters the
1. Pulmonary Ventilation
nasal cavity
 Air must move into and out of the lungs so
 Lined by cells that releases mucus,
that the gases in the alveoli of the lungs are
lysosome kills bacteria
continuously refreshed. This process of  Cilia at the entrance of nasal cavity is
pulmonary ventilation is commonly called coated with mucus
breathing.  Trap large particles of pollen and dust as
well as bacteria
2. External Respiration
 Forms tiny clumps of boogers (piece of
 Gas exchange (oxygen loading and carbon
dried nasal mucus)
dioxide unloading) between the
pulmonary blood and alveoli must take

22
 Uvula
 pendulum like, forms a flap or valve

Valve
 closes nasopharynx off when you eat to
prevent food going up into the
nasopharnyx

Cilia
 Cilia move mucus and trapped particles
from the nasal cavity to the pharynx.

 Clusters of lymphatic tissue called tonsils are

also found in the pharynx. The single
Paranasal Sinuses pharyngeal tonsil, often called the adenoid,
 Nasal cavity is connected to sinuses is located high in the nasopharynx.
 are air-filled spaces inside the bones  The two palatine tonsils are in the
that surround the nose oropharynx at the end of the soft palate,
 Helps air get warm and moist as well as the two lingual tonsils, which lie at
 Amplify the sound of your voice the base of the tongue. The tonsils also
 That's why you sound different when play a role in protecting the body from
your nose is clogged infection

Larynx
 The larynx is composed of a framework of
muscles and cartilages bound by elastic
tissue. The largest of thencartilages are the
thyroid (“Adam’s apple”), cricoid, and
epiglottic cartilages
 Inside the larynx, two pairs of horizontal
vocal folds composed of muscle tissue and
connective tissue with a covering of mucous
membrane extend inward from the lateral
Pharynx walls.
 The upper folds are called false vocal
Hard Palate cords because they do not produce
 the part you can feel with your tongue sounds
 The lower folds of muscle tissue and
Soft Palate elastic fibers are the true vocal cords.
 softer portion of the roof of your mouth
Laryngopharynx
Nasopharynx  the part of the pharynx that's continuous
 The region connecting nasal cavity and with larynx
pharynx
 Contracting or relaxing muscles that alter the
Oropharynx tension on the vocal cords controls the
 The region connecting oral cavity and pitch.
pharynx

23
The Heimlich Maneuver
 a procedure in which the air in a person’s
own lungs is used to “pop out,” or expel,
an obstructing piece of food, has saved
many people from becoming victims of
choking.

Epiglottis
 spoon shaped flap of cartilage acts like a lid
that seals of the airway when you're eating

 Cough reflex, if food gets into the larynx.

Trachea
 Air goes down into the trachea.
 The trachea is fairly rigid because its walls
are reinforced with C-shaped rings of
hyaline cartilage.
 These rings serve a double purpose. The
open parts of the rings abut the esophagus
and allow it to expand anteriorly when
we swallow a large piece of food. Visceral Pleura
 A layer of serous membrane, the visceral
pleura, firmly attaches to each lung surface
and folds back to become the parietal
pleura .

Parietal Pleura
 The parietal pleura, in turn, forms part of
the mediastinum and lines the inner wall
of the thoracic cavity.

Cilia
 The cilia are the yellow, grasslike projections
surrounded by the mucus-secreting goblet
cells, which exhibit short microvilli (orange).

Two Main Bronchi

Bronchi
 cartilage rings for support
 Right mainstem bronchus is wider and larger

Carina
 the point at which they split

24
Bronchioles  If a tiny particle ever makes it deep into the
 little bronchi can stay open without the lungs, there are alveolar macrophages that
need of cartilage can gobble it up and then physically
 conducting bronchioles - air is conducted move up to conducting bronchioles where
through smaller and smaller bronchioles they can ride the mucocilliary escalator all
for about 15 - 20 generations and receives the way up to the pharynx to be either
oxygenated blood from bronchial arteries coughed up or swallowed down.
 terminal bronchioles, are last generation of
conducting airways.
 respiratory bronchioles
 alveolar duct (final destination)

Alveoli
 500,000,000

 External respiration, gas transport, and

internal respiration: Gases move according
to the laws of diffusion.
 Oxygen moves from alveolar air into
 The respiratory zone, which includes the pulmonary blood. Most oxygen is
respiratory bronchioles, alveolar ducts, transported to hemoglobin bound inside
alveolar sacs, and alveoli, is the only site of RBCs.
gas exchange.  Carbon dioxide moves from pulmonary
blood into alveolar air. Most carbon dioxide
Alveolar Wall is transported as bicarbonate ion in plasma.
 no cilia or smooth mucle  At body tissues, oxygen moves from blood
 the walls are lined with thin epithelial cells to the tissues, whereas carbon dioxide
called pneumocytes moves from the tissues to blood.

Pneumocytes Fact:
 If all of the capillaries that surround the
a. Type 1 Pneumocyte: The cell responsible alveoli were unwound and laid end to
for the gas (oxygen and carbon dioxide) end, they would extend for about 620
exchange that takes place in the alveoli. miles.
b. Type 2 Pneumocyte: The cell responsible
for the production and secretion of Gas Exchange
surfactant.
c. Surfactant: reduces the surface tension of 1. Free from particles, the inhaled air is now in
pulmonary fluids and contributes to the the alveolus surrounded by mostly type 1
elastic properties of the lungs, Keeps pneumocytes.
Alveoli Open!
2. On the other side of the pneumocytes are
endothelial cells that line the capillary walls,
which is what holds the blood.

3. This time though that blood comes from the

pulmonary arteries and is deoxygenated,
the pneumocytes and the capillaries are
glued together with a protein layer called
the basement membrane.

25
 breathing.
4. So, the alveolar wall, the basement Volition To a degree, breathing may be
membrane and the capillary wall is really consciously controlled if it does not
all that separates the air from the blood, and interfere with homeostasis.
this is called the blood gas barrier. Emotional Some emotional stimuli can modify
Factors breathing. Examples are fear,
anger, and excitement.
5. At this point carbon dioxide diffuses out Chemical Changes in carbon dioxide levels
from the deoxygenated blood, and into Factors are the most important stimuli
the air of the alveoli, which then gets affecting respiratory rhythm and
breathed out, and with each breath in. depth. Carbon dioxide acts directly
on the medulla via its effect on
6. Oxygen enters the alveoli and freely diffuses reducing the pH of blood and
into the blood, that freshly oxygenated brainstem tissue.
blood then heads off to the pulmonary veins,
the heart and then to the body's tissues. Respiratory Sounds

Sound Mechanism
Vesicular - Vesicular breath sounds are soft
Normal and low pitched with a rustling
quality during inspiration and are
even softer during expiration.
Crackles - Fine Fine crackles are brief,
(Rales) discontinuous, popping lung
sounds that are high-pitched. Fine
crackles are also similar to the
sound of wood burning in a
fireplace, or hook and loop
fasteners being pulled apart or
cellophane being crumpled.
Crackles - Coarse Coarse crackles are discontinuous,
 Oxygen (O2) diffuses from air within the (Rales) brief, popping lung sounds.
alveolus into the capillary, while carbon Compared to fine crackles they are
dioxide (CO2) diffuses from blood within louder, lower in pitch and last
the capillary into the alveolus. longer. They have also been
described as a bubbling sound.
Wheeze Wheezes are adventitious lung
sounds that are continuous with a
musical quality. Wheezes can be
high or low pitched. High pitched
wheezes may have an auscultation
sound similar to squeaking. Lower
pitched wheezes have a snoring or
moaning quality.
Rhonchi - Low Low pitched wheezes (rhonchi) are
Pitched Wheezes continuous, both inspiratory and
expiratory, low pitched
adventitious lung sounds that are
Control Of Respiration similar to wheezes. They often
have a snoring, gurgling or
rattle-like quality.
Nervous Neural centers for control of
Control respiratory rhythm are in the Bronchial Brochial sounds are hollow,
medulla and pons. The medulla is tubular sounds that are lower
the respiratory rate “pacemaker.” pitched, They can be auscultated
Reflex arcs initiated by stretch over the trachea where they are
receptors in the lungs also play a considered normal.
role in respiration by notifying Pleural Rubs Pleural rubs are discontinuous or
neural centers of excessive over continuous, creaking or grating
inflation. sounds. The sound has been
Physical Factors Increased body temperature, described as similar to walking on
exercise, speech, singing, and fresh snow or a leather-on-leather
non-respiratory air movements type of sound.
modify both rate and depth of Bronchovesicular Inspiration to expiration periods

26
 are equal, these are normal sounds Cheyne-Stokes Gradual increase in
in the mid-chest area or in the respirations (CSR) volume and frequency,
posterior chest between the followed by a gradual
scapula. decrease in volume and
frequency,
Nonrespiratory Air (Gas) Movements with apnea periods of 10 -
30 seconds between
cycle. Described as a
Movement Mechanism and Result
crescendo - decrescendo
Cough Taking a deep breath, closing
pattern.
glottis, and forcing air superiorly
from lungs against glottis. Then,
glottis opens suddenly, and a blast Acid Base Balance Regulation
of air rushes upward. Coughs act
to clear the lower respiratory Acid–base Imbalance
passageways.  is an abnormality of the human body's
Sneeze Similar to a cough, except that normal balance of acids and bases that
expelled air is directed through causes the plasma pH to deviate out of the
nasal cavities instead of through normal range (7.35 to 7.45).
oral cavity. The uvula , a dangling
tag of tissue hanging from the soft
palate, becomes depressed and Alkalosis
closes oral cavity off from  Increase in blood pH
pharynx, routing air through nasal
cavities. Sneezes clear upper Acidosis
respiratory passages.  Decrease in blood pH
Crying Inspiration followed by release of
air in a number of short Respiratory Acidosis
expirations. Primarily an  Too much intake of CO2
emotionally induced
mechanism.
Respiratory Alkalosis
Laughing Essentially same as crying in terms
of the air movements produced.  Excess loss of CO2
Also an emotionally induced
response. Metabolic Acidosis
Hiccups Sudden inspirations resulting from  Excess hydrogen ion
spasms of diaphragm; initiated by
irritation of diaphragm or phrenic Metabolic Alkalosis
nerves, which serve diaphragm.  Excess hyrdogen ion loss or excess alkaline
The sound occurs when inspired intake
air hits vocal folds of closed
glottis.
Yawn Very deep inspiration, taken with
Essence of the Substance
jaws wide open; ventilates all
alveoli (some alveoli may remain  The nasal cavity is lined with mucosa, which
collapsed during normal quiet warms, filters, and moistens incoming air.
breathing).  The pharynx (throat) is a mucosa-lined,
muscular tube with three
Abnormal Breathing Patterns regions—nasopharynx, oropharynx, and
laryngopharynx
Pattern Mechanism  The larynx contains the vocal folds (true
Tachypnea Increased frequency vocal cords), which produce sounds used in
without blood gas speech.
abnormality  The trachea is a smooth-muscle tube lined
Kussmaul's Increased rate and depth with a ciliated mucosa and reinforced with
Respiration of breathing over a
C-shaped cartilaginous rings, which keep
prolonged period of
time. In response to the trachea patent (open).
metabolic acidosis, the  Right and left main (primary) bronchi result
body's attempt to blow from division of the trachea. Each plunges
off CO2 to buffer a fixed into the hilum of the lung on its side.
acid such as ketones.  The lungs are paired organs flanking the
Ketoacidosis is seen in mediastinum in the thoracic cavity.
diabetics.

27
 The lungs are primarily elastic tissue and Fats = Fatty Acids
passageways of the bronchial tree. The
smallest passageways end in clusters of air
sacs called alveoli.
 The conducting zone includes all respiratory
passages from the nasal cavity to the
terminal bronchioles; they conduct air to
and from the alveoli of the lungs.
 Gas travels from high pressure to
low-pressure areas. Pressure outside the
body is atmospheric pressure; pressure
inside the lungs is intrapulmonary pressure;
pressure between the pleurae is
intrapleural pressure.
 Nonrespiratory air movements: These are
voluntary or reflex activities that move air
into or out of the lungs. Human Digestive System
 Respiratory sounds: Bronchial sounds are
sounds of air passing through large
respiratory passageways. Vesicular
breathing sounds occur as air fills alveoli.
 The major respiratory disorders are COPD
(emphysema and chronic bronchitis) and
lung cancer. Cigarette smoking is a
significant cause of both.
 Emphysema is characterized by permanent
destruction and enlargement of alveoli.
 Chronic bronchitis is characterized by
excessive production and pooling of mucus
in lower respiratory passageways, which
severely impairs ventilation and gas
exchange.
 Lung cancer is extremely aggressive and
metastasizes rapidly.

Lesson 4: Human Digestive System and Body

 After chewing and swallowing, it takes 5
Metabolism
to 10 seconds for food to pass down the
esophagus to the stomach, where it
spends 2 to 6 hours being partially
digested.
 Final digestion and nutrient absorption
occur in the small intestine over a period
of 5 to 6 hours.
 In 12 to 24 hours, any undigested
material passes through the large
intestine, and feces are expelled through
the anus.

Overview of the Digestive System

Digestive Tract (Alimentary Organs):

 Mouth, pharynx, and esophagus,
stomach, small intestine, and large
Building Blocks of…
intestine (colon)
Carbohydrates = Glucose/Monosaccharides
Proteins = Amino Acids

28
Accessory Organs:
 Teeth, tongue, salivary glands, pancreas,
liver, and gallbladder

Mouth

Diagram of Teeth

Babies = 20 teeth

GI or Alimentary Tract Ingestion

 is a continous coiled hollow, muscular  placing food in the mouth
tube that winds through the ventral
body cavity and is open at both ends. Mouth

a. mechanical digestion – mastication

(chewing food)
 teeth

29
  breaking up food Pharynx
 The back of the throat.
b. chemical digestion
 saliva Larynx
 amylase  passage for air, closes when we swallow.
 enzyme digests starch  Is approximately 15cm long.
 mucin  Passageway of air and food/liquid that is
 slippery protein (mucus) branched out towards trachea (air) and
 protects soft lining of digestive esophagus (food/liquid)
system
 lubricates food for easier Swallowing (& not choking)
swallowing
 buffers Epiglottis
 neutralizes acid to prevent tooth  flap of cartilage
decay  closes trachea (windpipe) when
 anti-bacterial chemicals swallowing
 kill bacteria that enter mouth with  food travels down esophagus
food
Peristalsis
Salivary Amylase  involuntary muscle contractions to move
 protein enzyme in saliva that moisture food along
food for custom swallowing

Mechanical Digestion
 can still see the food as it is

Chemical Digestion
 enzymes help in food digestion

Esophagus
 Pushes food to Stomach

Type of Digestion Examples:

1. Chewing a saltine? – Mechanical

2. Saliva breaking the saltine down into
molecules of glucose? – Chemical
3. Your tongue breaking pieces of a
hamburger apart? – Mechanical
4. Pepsin (an enzyme) in your stomach
breaking the hamburger into amino acids?
– Chemical

30
Motility: Peristalsis  Pepsin breaks down proteins (only at pH
2)
 Food is temporarily stored here up to
2-4 hours
 Pushes food through pyloric sphincter to
small intestine
 Has layers of muscle that line the inside.

Stomach’s Opening:

a. Esophageal Sphincter – entry of food to

stomach
b. Pyloric Sphincter – exit of food to
stomach

Peristalsis Parts of Stomach

 series of involuntary wave-like muscle
contractions which move food along the 1. Cardia
digestive tract 2. Fundus
3. Body of stomach
4. Pylorus

Stomach Functions
 Mechanically and chemically breaks  food storage
down food  can stretch to fit ~2L food
 Glands produce gastric juice = pepsin +  disinfect food
HCl  HCl = pH 2
 bacteria

31
  chemical digestion
 pepsin
 enzyme breaks down proteins

Mucus Secreted by Stomach Cells

 protects stomach lining
 stops the stomach from digesting itself

 Still, the epithelium is continually eroded,

and the epithelium is completely
replaced by mitosis every three days.
 Gastric ulcers, lesions in the stomach
lining, are caused by the acid-tolerant
bacterium Heliobacter pylori. Accessory Organs
 Ulcers are often treated with antibiotics.
 Pepsin is secreted in an inactive form,
called pepsinogen by specialized chief
cells in gastric pits.
 Parietal cells, also in the pits, secrete
hydrochloric acid which converts
pepsinogen to the active pepsin only
when both reach the lumen of the
stomach, minimizing self-digestion.
 Also, in a positive-feedback system,
activated pepsin can activate more
pepsinogen molecules.

1. Gall Bladder
 Pouch structure located near the liver
which concentrates and stores bile
 Bile duct – a long tube that carries BILE.
The top half of the common bile duct is
associated with the liver, while the
bottom half of the common bile duct is
associated with the pancreas, through
which it passes on its way to the
intestine.

Bile
 Bile emulsifies lipids (physically breaks
apart FATS)
 Bile is a bitter, greenish-yellow alkaline
fluid, stored in the gallbladder between
Gastric Juices meals and upon eating is discharged into
 Secreted by the stomach. the duodenum where it aids the process
 Acidic (pH 1.5-2.5) (HCl). of digestion.
 Pepsin - an enzyme that breaks down
large proteins into amino acids. 2. Pancreas
 Food is further broken down into a thin  An organ which secretes both digestive
liquid called chyme. enzymes (exocrine) and hormones
 Bolus – food after passing the mouth (endocrine)

32
  Pancreatic juice digests all major nutrient  small intestine has huge surface area
types. = 300m2 (~size of tennis court)
 Nearly all digestion occurs in the small
intestine & all digestion is completed in Structure
the SI.  3 sections
 duodenum = most digestion
Pancreas are…  jejunum = absorption of nutrients &
water
a. Digestive Enzymes  ileum = absorption of nutrients &
 digest proteins water
 trypsin, chymotrypsin
 digest starch  About every 20 seconds, the stomach
 amylase contents are mixed by the churning
action of smooth muscles.
b. Buffers  As a result of mixing and enzyme action,
 neutralizes acid from stomach what begins in the stomach as a recently
swallowed meal becomes a nutrient-rich
broth known as acid chyme.
 At the opening from the stomach to the
small intestine is the pyloric sphincter,
which helps regulate the passage of
chyme into the intestine.
 A squirt at a time, it takes about 2 to 6
hours after a meal for the stomach to
empty.

3. Liver

Function
 produces bile
 bile stored in gallbladder until
needed
 breaks up fats
 act like detergents to breakup fats

Bile
 bile contains colors from old red blood
cells collected in liver = iron in RBC rusts Duodenum
& makes feces brown  1st section of small intestines
 acid food from stomach
4. Small Intestine  mixes with digestive juices from:
 Most chemical digestion takes place here.  pancreas
 Simple sugars and proteins are absorbed  liver
into the inner lining.  gall bladder
 Fatty acids and glycerol go to lymphatic
system. Absorption in the Small Intestine
 Lined with villi, which increase surface  Much absorption is thought to occur
area for absorption, one cell thick. directly through the wall without the
need for special adaptations
Function  Almost 90% of our daily fluid intake is
 chemical digestion absorbed in the small intestine.
 major organ of digestion &  Villi - increase the surface area of the
absorption small intestines, thus providing better
 absorption through lining absorption of materials
 over 6 meters!

33
Absorption by Small Intestines Parts of the Colon
 Absorption through villi & microvilli
 finger-like projections 1. Ascending colon
 increase surface area for absorption 2. Transverse colon
3. Descending colon
4. Sigmoid

Escherichia Coli (E. coli)

 Living in the large intestine is a
community of helpful bacteria
 produce vitamins
 vitamin K; B vitamins
 generate gases
 by-product of bacterial metabolism
 methane, hydrogen sulfide

Vestigial Organ

Villi

5. Large Intestines (Colon)

Colonoscopy Rectum
 examining the large intestine for any  Last section of colon (large intestines)
cancers  eliminate feces
 undigested materials
Function  extracellular waste
 re-absorb water o mainly cellulose from plants
 use ~9 liters of water every
o roughage or fiber
day in digestive juices
 masses of bacteria
 90% of water reabsorbed

Diarrhea
 not enough water absorbed
 “soft feces”

Constipation
 too much water absorbed
 “hard feces”

 Solid materials pass through the large

intestine.
 These are undigestible solids (fibers).
 Water is absorbed. Functions of the Digestive System
 Vitamins K and B are reabsorbed with
the water. 1. Ingestion
 Rectum - solid wastes exit the body. 2. Mechanical processing
3. Chemical digestion
4. Secretion

34
 5. Absorption Flow Chart of Digestion
6. Excretion

Appendicitis
 Inflammation of the appendix

Appendectomy
 Removal of appendix

Defecation
 Elimination of waste (feces)

Fecalysis
 Analyzing feces

Urinalysis
 Analyszing urine

Body Metabolism Metabolism

 A broad term of all chemical reactions
that are necessary to maintain life
referring

Involves:
 Catabolism - breaking down of substance
to a simpler form (large to small)
 Anabolism - formation of larger
molecules are built from smaller
substance (small to large)

35
Lesson 5: The Urinary System

Organs of the Urinary system

 Kidneys
 Ureters
 Urinary bladder
 Urethra

Kidney Structures

1. Medullary pyramids – triangular regions of

tissue in the medulla
2. Renal columns – extensions of cortex-like
material inward
3. Calyces – cup-shaped structures that funnel
Functions of the Urinary System urine towards the renal pelvis
 Elimination of waste products
 Nitrogenous wastes Coverings of the Kidneys
 Toxins  Renal capsule
 Drugs  Surrounds each kidney
 Regulate aspects of homeostasis  Adipose capsule
 Water balance  Surrounds the kidney
 Electrolytes  Provides protection to the kidney
 Acid-base balance  Helps keep the kidney in its correct
 Blood pressure location
 RBC production
 Activation of vit.D Blood Flow in the Kidneys

Location of the Kidneys

 Against the dorsal body wall
 At the level of T12 to L3
 The right kidney is slightly lower than the
left
 Attached to ureters, renal blood vessels, and
nerves at renal hilus
 Atop each kidney is an adrenal gland

Regions of the Kidney Nephrons

 The structural and functional units of the
1. Renal cortex – outer region kidneys
2. Renal medulla – inside the cortex  Responsible for forming urine
3. Renal pelvis – inner collecting tube  Main structures of the nephrons
 Glomerulus
 Renal tubule

Glomerulus
 A specialized capillary bed

36
 Attached to arterioles on both sides
(maintains high pressure)
 Large afferent
arteriole
 Narrow efferent
arteriole

2. Juxtamedullary Nephrons
 Found at the boundary of the cortex and
medulla

Peritubular Capillaries
 Arise from efferent arteriole of the
glomerulus
 Normal, low pressure capillaries
 Attached to a venule
 The glomerulus sits within a glomerular  Cling close to the renal tubule
capsule (the first part of the renal tubule)  Reabsorb (reclaim) some substances from
collecting tubes
Renal Tubule
 Glomerular (Bowman’s) capsule Urine Formation Processes
 Proximal convoluted tubule
 Loop of Henle 1. Filtration
 Distal convoluted tubule  Nonselective passive process
 Water and solutes smaller than proteins are
forced through capillary walls
 Blood cells cannot pass out to the capillaries
 Filtrate is collected in the glomerular capsule
and leaves via the renal tubule

2. Reabsorption
 The peritubular capillaries reabsorb several
materials
 Some water
 Glucose
 Amino acids
 Ions
 Some reabsorption is passive, most is active
 Most reabsorption occurs in the proximal
convoluted tubule

Materials Not Reabsorbed

 Nitrogenous waste products
 Urea
 Uric acid
Types of Nephrons  Creatinine
 Excess water
1. Cortical Nephrons
 Located entirely in the cortex 3. Secretion (Reabsorption in Reverse)
 Includes most nephrons  Some materials move from the peritubular
capillaries into the renal tubules

37
  Hydrogen and potassium ions  Slightly aromatic
 Creatinine  Normal pH of around 6 (varies 4.5-8)
 Materials left in the renal tubule move  Specific gravity of 1.001 to 1.035
toward the ureter
Ureters
 Slender tubes attaching the kidney to the
bladder
 Continuous with the renal pelvis
 Enter the posterior aspect of the
bladder
 Runs behind the peritoneum
 Peristalsis aids gravity in urine transport

Urinary Bladder
 Smooth, collapsible, muscular sac
 Temporarily stores urine

 Trigone – three openings

 Two from the ureters
 One to the urethrea

Urinary Bladder Wall

 Three layers of smooth muscle (detrusor
muscle)
 Mucosa made of transitional epithelium
 Walls are thick and folded in an empty
bladder
 Bladder can expand significantly without
increasing internal pressure

Urethra
 Thin-walled tube that carries urine from the
bladder to the outside of the body by
peristalsis
 Release of urine is controlled by two
sphincters
 Internal urethral sphincter (involuntary)
 External urethral sphincter (voluntary)

Characteristics of Urine Used for Medical Urethra Gender Differences

Diagnosis  Length
 Colored somewhat yellow due to the  Females – 3–4 cm (1 inch)
pigment urochrome (from the destruction of  Males – 20 cm (8 inches)
hemoglobin) and solutes  Location
 Sterile  Females – along wall of the vagina

38
  Males – through the prostate and penis  Sources for water intake
 Function  Ingested foods and fluids
 Females – only carries urine  Water produced from metabolic
 Males – carries urine and is a processes
passageway for sperm cells  Sources for water output
 Vaporization out of the lungs
Micturition (Voiding)  Lost in perspiration
 Both sphincter muscles must open to allow  Leaves the body in the feces
voiding  Urine production
 The internal urethral sphincter is  Dilute urine is produced if water intake is
relaxed after stretching of the bladder excessive
 Activation is from an impulse sent to  Less urine (concentrated) is produced if large
the spinal cord and then back via the amounts of water are lost
pelvic splanchnic nerves  Proper concentrations of various electrolytes
 The external urethral sphincter must be must be present
voluntarily relaxed
Regulation of Water and Electrolyte
Maintaining Water Balance Reabsorption
 Normal amount of water in the human  Regulation is primarily by hormones
body  Antidiuretic hormone (ADH) prevents
 Young adult females – 50% excessive water loss in urine
 Young adult males – 60%  Aldosterone regulates sodium ion
 Babies – 75% content of extracellular fluid
 Old age – 45%  Triggered by the
 Water is necessary for many body functions rennin-angiotensin mechanism
and levels must be maintained  Cells in the kidneys and hypothalamus are
active monitors
Distribution of Body Fluid
 Intracellular fluid (inside cells) Maintaining Water/Electrolyte Balance
 Extracellular fluid (outside cells)
 Interstitial fluid
 Blood plasma

The Link Between Water and Salt

 Changes in electrolyte balance causes water
to move from one compartment to another
 Alters blood volume and blood
pressure
 Can impair the activity of cells

Maintaining Water Balance

 Water intake must equal water output

39
Maintaining Acid-Base Balance in Blood Gonads
 Blood pH must remain between 7.35 and
7.45 to maintain homeostasis
 Alkalosis – pH above 7.45
 Acidosis – pH below 7.35
 Most ions originate as byproducts of cellular
metabolism
 Most acid-base balance is maintained by the
kidneys
 Other acid-base controlling systems
 Blood buffers
 Respiration

Developmental Aspects of the Urinary System

 Functional kidneys are developed by the
third month
 Urinary system of a newborn
 Bladder is small
 Urine cannot be concentrated
 Control of the voluntary urethral sphincter
does not start until age 18 months
 Urinary infections are the only common
problems before old age

Aging and the Urinary System Male Reproductive System

 There is a progressive decline in urinary
function
 The bladder shrinks with aging
 Urinary retention is common in males

Lesson 6: Reproductive System (1)

Reproductive System
 Composed of organs grouped together for
1 common function – to produce or
multiply species of the same kind.
 The purpose is to ensure the “survival of
the species”
 Both male and female reproductive organs
have internal and external structures.
 Reproductive organs are considered to be
either primary or secondary organs.
 The primary reproductive organs are the
gonads (ovaries and testes), which are
responsible for gamete (sperm and egg cell)
and hormone production.

Functions of Reproductive System

1. to produce egg and sperm cells (gametes)

2. to transport and sustain these cells
3. to nurture a developing offspring
4. to produce sex hormones

Gametes
 are the basic units of sexual reproduction

40
 2. Lobules – compartments formed by the
septae
3. Seminiferous tubules – actual site of
spermatogenesis; formed by two types of
cell.
a. Spermatogenic cells – includes
spermatids, spermatogonia,
spermatocytes
b. sustentacular (sertoli) cells) – provide
nourishment for thegerminal sperm
1.2.1. Testes 4. Interstitial cell of leydig – secretes male sex
 Each testis is connected to the trunk via the hormone- “testosterone”
spermatic cord, which houses:
 Blood vessels 1.2.2 Duct System
 Nerves
 Ductus/vas deferens

Coverings Of The Testes

1. Tunica albuginea — capsule that surrounds

each testis
2. Septa — extensions of the capsule that
extend into the testis and divide it into
lobules

 Each lobule contains one to four

seminiferous tubules
 Tightly coiled structures
 Function as sperm-forming factories
 Empty sperm into the rete testis

 Sperm travels from the rete testis to the

epididymis
 Interstitial cells in the seminiferous tubules
produce androgens such as testosterone

1.2.3 Accessory Organs and Semen

a. 1.2.3.1 Seminal Glands (Vesicles)

b. 1.2.3.2 Prostate
c. 1.2.3.3 Bulbourethral Gland
d. 1.2.3.4 Semen

1.2.4 External Genitalia

a. 1.2.4.1 Scrotum
 Divided sac of skin outside the abdomen
Structures Of The Gonads that houses the testes
 Viable sperm cannot be produced at normal
1. Septae – a partition formed inside the testes body temperature (3°C)

41
  composed of 3 cylindrical columns of
b. 1.2.4.2 Penis erectile tissue: corporacavernosa (2),
 Male organ of copulation that delivers corpora spongiosa (1)
sperm into the female rt

 Internally there are three areas of spongy

erectile tissue around the urethra
 Erections occur when this erectile tissue fills
with blood during sexual excitement

3 Parts of the Penis

1. Root of the penis

 attached portion to the abdominal wall

2. Body of the penis

Parts Of The Male Reproductive Organ  composed of erectile tissue

1. Scrotum 3. Glans penis

 a sac or pouch like structure that hangs  cone-shaped terminal portion of the
from the root of the penis, composed of penis, consists of the following structure:
loosed skin, superficial fascia, and muscles. corona, external urethral meatus, prepuce
 Vertical septum divides the scrotum into (foreskin), frenulum
two sacs, containing a single testis function
to support and protect the testes and
maintain the temperature of the testes at
about 35°C
 Divided sac of skin outside the abdomen
that houses the testes
 Viable sperm cannot be produced at
normal body temperature (3°C)

Chief Roles Of The Male In The Reproductive

Process
 Produce sperm
 Produce a hormone, testosterone

1.3.1 Spermatogenesis
2. Penis
 is the main copulatory organ of the male Sperm Production
reproductive system.  Begins at puberty and continues throughout
life

42
 Millions of sperm are made every day  Prostate cancer that's detected early —
 Sperm are formed in the seminiferous when it's still confined to the prostate gland
tubules of the testis — has the best chance for successful
 Spermatogonia (primitive stem cells) begin treatment.
the process by dividing rapidly
 During puberty, follicle-stimulating Symptoms
hormone (FSH) is secreted in increasing  Prostate cancer may cause no signs or
amounts symptoms in its early stages.
 Prostate cancer that's more advanced may
cause signs and symptoms such as:
 Trouble urinating
 Decreased force in the stream of urine
 Blood in the urine
 Blood in the semen
 Bone pain
 Losing weight without trying
 Erectile dysfunction

When to see a doctor?

 Make an appointment with your doctor if
you have any persistent signs or symptoms
that worry you.

1.3.2 Testosterone Production

During Puberty
a. Follicle-Stimulating Hormone (FSH)
 begins prodding seminiferous tubules to
produce sperm

b. Luteinizing Hormone (LH)

 begins activating the interstitial cells to
produce testosterone

Testosterone
 Most important hormonal product of the
testes
 Stimulates reproductive organ development
 Underlies sex drive
 Causes secondary sex characteristics
 Increased hair growth
 Enlargement of skeletal muscles
 Increased bone growth and density
Prostate Cancer
 Prostate cancer is cancer that occurs in the The Female Reproductive System
prostate.  Composed of organs grouped together for 1
 The prostate is a small walnut-shaped gland common function – to produce or multiply
in males that produces the seminal fluid that species of the same kind.
nourishes and transports sperm.  The purpose is to ensure the “survival of the
 Prostate cancer is one of the most common species”
types of cancer.  Production of gametes (ova, or eggs)
 Many prostate cancers grow slowly and are  Preparation for support of developing
confined to the prostate gland, where they embryo during pregnancy
may not cause serious harm.  Cyclic changes: menstrual cycle
 However, while some types of prostate  Averages 28 days
cancer grow slowly and may need minimal
or even no treatment, other types are
aggressive and can spread quickly.

43
 Complex interplay between hormones and  A virgin is someone who’s never had sex.
organs: at level of brain, ovaries and But people define “sex” and “losing
uterus virginity” in many different ways.

1.4.0 Reproductive System: Anatomy Virgin

 A virgin is someone who’s never had sex —
1.4.1 Ovaries but it’s not quite as simple as it seems. That’s
 Produce eggs (ova) and hormones (estrogen because sex means different things to
and progesterone different people, so virginity can mean
 Each ovary houses ovarian follicles different things, too.
consisting of:
 Oocyte (immature egg) Hymen
 The hymen is a thin, fleshy tissue that's
 Follicle cells — layers of different cells located at the opening of your vagina. ...
that surround the oocyte Just like other parts of our body, hymens are
a little different for everyone. Your hymen
can be stretched open the first time you
have vaginal sex, which might cause some
pain or bleeding. But this doesn't happen to
everyone.

What happens if hymen break?

 Some women will bleed after having
sex for the first time, while others will not.
Both are perfectly normal. A woman may
bleed when she has penetrative sex for the
first time because of her hymen stretching or
tearing. The hymen is a thin piece of skin
that partially covers the entrance to the
vagina.
1.4.2 Duct System 1.4.2.1 Uterine (Fallopian) tubes
 Form the initial part of the duct system
 Receive the ovulated oocyte from the
ovaries
 Provide a site for fertilization
 Empty into the uterus
 Little or no contact between ovaries and
uterine tubes
 Supported and enclosed by the broad
ligament

Uterine (Fallopian) Tube Structure

1. Infundibulum: Distal, funnel-shaped end
2. Fimbriae: Fingerlike projections of the
infundibulum
3. Ampulla: widest section of the uterine tubes.
Fertilization usually occurs here.
Virginity
 Losing your virginity means having sex for  Receive the oocyte from the ovary
the first time. The idea of virginity can apply  Cilia located inside the uterine tube
to people of any gender or sexual transport the oocyte
orientation. There is no strict definition of
virginity, because there is no strict definition Uterine (Fallopian) Tubes
of sex.  or oviducts, a two long, slender tubes that
connect the ovaries to the uterus. Eggs pass

44
 from the ovaries, through the fallopian The Four Phases Of The Menstrual Cycle
tubes, to the uterus.  are the follicular phase, ovulation and the
luteal phase, and menstruation.
1.4.2.2 Uterus  Common menstrual problems include heavy
 Situated between the urinary bladder and or painful periods and premenstrual
rectum syndrome (PMS).
 Receives, retains, nourishes a fertilized egg

Layers Of The Uterus

1. Endometrium
 Inner layer (mucosa)
 Site of implantation of a fertilized egg
 Sloughs off if no pregnancy occurs
(menstruation or menses)

2. Myometrium
 is the middle layer of smooth muscle that
contracts during labor

3. Perimetrium (visceral peritoneum)

 is the outermost serous layer of the uterus

Uterus
 also known as the womb, and a hollow
muscular organ located in the female pelvis
between the bladder and rectum. Once the
egg has left the ovary it can be fertilized and 1.4.2.3 Vagina
implant itself in the lining of the uterus. The  Passageway that extends from cervix to
main function of the uterus is to nourish the exterior of body and is located between
developing fetus prior to birth. This is urinary bladder and rectum
responsible for many functions in the  Serves as the canal that allows a baby or
processes of implantation, gestation, menstrual flow to leave the body
menstruation, and labor.  Female organ of copulation
 Receives the penis during sexual intercourse
 Hymen — partially closes the vagina until it
is ruptured

Vagina
 a fibro-muscular tubular organ, about 3-4
in long and extends from the cervix of the
uterus to the outside.

1.4.3 External Genitalia

Menstrual Cycle The female external genitalia, or vulva, includes:

 Mons pubis
 Labia
 Clitoris
 Urethral orifice
 Vaginal orifice
 Greater vestibular glands

The Bartholin's Glands (Or Greater Vestibular

Glands)
 are important organs of the female
reproductive system. The primary function is

45
 the production of a mucoid secretion that  Structures that support the urogenital and
aids in vaginal and vulvar lubrication. gastrointestinal systems – and it therefore
plays an important role in functions as such
micturition, defecation, sexual intercourse
and childbirth.

Female Reproductive Functions And Cycles

 The total supply of eggs is determined by
the time a female is born
 Ability to release eggs begins at puberty with
the onset of the menstrual cycle
 Reproductive ability ends at menopause (in
female’s fifties)

1.5. Reproductive System: Female Reproductive

Functions And Cycles

11.5.1 Oogenesis and the Ovarian Cycle

 Oogenesis is the process of producing ova
11.4.3.1 Mons Pubis (eggs) in a female
 Fatty area overlying the pubic symphysis  Oogonia are female stem cells found in a
 Covered with pubic hair after puberty developing fetus
 Oogonia undergo mitosis to produce
11.4.3.2 External Genitalia and Perineum primary oocytes that are surrounded by cells
that form primary follicles in the ovary
11.4.3.2.1 Labia – skin folds  Primary oocytes are inactive until puberty
 Labia majora  Follicle-stimulating hormone (FSH) causes
 Hair-covered skin folds some primary follicles to mature each
 Enclose the labia minora month
 Also encloses the vestibule  Cyclic monthly changes constitute the
 Labia minora—delicate, hair-free folds of ovarian cycle
skin  Meiosis starts inside maturing follicle
 First meiotic division produces a larger
Vestibule secondary oocyte and a smaller first polar
 Enclosed by labia majora body
 Contains external openings of the urethra  A vesicular follicle contains a secondary
and vagina oocyte (maturation from a primary follicle
takes about 14 days)
Greater Vestibular Glands  Ovulation of a secondary oocyte occurs
 One is found on each side of the vagina with the release of luteinizing hormone (LH)
 Secretions lubricate vagina during  Secondary oocyte is released and
intercourse surrounded by a corona radiata

11.4.3.2.2 Clitoris 11.5.2 Hormone Production by the Ovaries

 Contains erectile tissue
 Corresponds to the male penis Estrogens are produced by follicle cells
 The clitoris is similar to the penis in that it is:  Cause secondary sex characteristics
 Hooded by a prepuce  Enlargement of accessory organs of the
 Composed of sensitive erectile tissue female reproductive system
 Swollen with blood during sexual  Development of breasts
excitement  Appearance of axillary and pubic hair
 The clitoris lacks a reproductive duct  Increase in fat beneath the skin, particularly
in hips and breasts
11.4.3.2.3 Perineum  Widening and lightening of the pelvis
 Diamond-shaped region between the  Onset of menses (menstrual cycle)
anterior ends of the labial folds, anus
posteriorly, and vischial tuberosities laterally

46
Progesterone is produced by the corpus luteum Lesson 6: Reproductive System (2)
 Production continues until LH diminishes in
the blood Histology of the Male Reproductive System
 Does not contribute to the appearance of
secondary sex characteristics Male Reproductive System
 Other major effects
 Helps maintain pregnancy 1. Testis
 Prepares the breasts for milk production 2. Genital Ducts
3. Accessory Glands
11.5.3 Uterine (Menstrual) Cycle 4. Penis
 Cyclic changes of the endometrium, about
28 days in length The Testes and Seminiferous Tubules
 Regulated by cyclic production of estrogens
and progesterone by the ovaries Testes
 FSH and LH, from the anterior pituitary,  The most essential organs of the male
regulate the production of estrogens and reproductive system.
progesterone by the ovaries  Contains tubules and cells responsible for
 Ovulation typically occurs about midway the production of testosterone and
through cycle, on day 14 sperm.
 Stages of the menstrual cycle
 Menstrual phase Seminiferous Tubules
 Proliferative stage  Site of Spermatogenesis
 Secretory stage
Interstitial Cell / Leydig Cells
 Responsible for the production of
Testosterone.

Spermatogenesis

11.5.4 Mammary Glands

 Present in both sexes, but function only in
females
 Modified sweat glands
 Function is to produce milk to nourish a
newborn
 Stimulated by sex hormones (mostly
estrogens) to increase in Size

Parts Of The Mammary Gland

1. Areola — central pigmented area

2. Nipple — protruding central area of areola
3. Lobes — internal structures that radiate
around nipple
4. Lobules — located within each lobe and
contain clusters of alveolar
5. Glands § Alveolar glands — produce milk
when a woman is lactating (producing milk)
6. Lactiferous ducts — connect alveolar glands
to nipple
7. Lactiferous sinus — dilated portion where
milk accumulates

47
 Genital Ducts

1. Epididymis
 Site of sperm maturation.
 Short – term storage of sperm.
 Expels Sperm during ejaculation.

2. Neutral alpha – glucosidase (NAG)

 specific marker for epididymal secretion in
seminal pathology.

3. Ductus deferens / Vas deferens

 Carries sperm by rapid peristalsis from the
epididymis to the ejaculatory ducts.

Spermiogenesis 4. Ejaculatory Duct

 Process of cell differentiation by which  Mix sperm and seminal fluid; deliver
spermatids become sperm. semen to urethra, where prostatic
 The major changes that occur during secretion is added.
spermiogenesis are shown here.
 These involve flattening of the nucleus, Accessory Glands
formation of an acrosome, growth of a
flagellum (tail) from the basal body, 1. Seminal Vesicles
reorganization of the mitochondria in the  Secretes 70% of the fluid in the semen /
mid piece region, and shedding of unneeded ejaculate.
cytoplasm.
2. Fructose
 Major energy source for sperm

3. Prostaglandins
 Stimulate activity in the female reproductive
tract.

4. Fibrinogen
 Allows semen to coagulate after ejaculation.

5. Flavin
 Responsible for the gray to opalescent
appearance of semen.

6. Prostate Gland
 Collection of 30 to 50 tubuloacinar glands
embedded in a dense fibromuscular stroma
in which smooth muscle contracts at
ejaculation.

7. Zinc
 Present in higher concentration in the
Prostate and may be associated with
Prostate health.

8. Bulbourethral Gland / Cowper’s Gland

 Secretes alkaline mucus to neutralizes
vaginal and prostatic acidity.

48
The Penis Oogenesis and Ovarian Cycle

Sympathetic
 Stimulate at ejaculation.
 Constricts blood flow through the helicine
arteries, allowing blood to empty from the
cavernous tissues.

Parasympathetic
 Erection
 Stimulate during relaxation of muscle of the
small helicine arteries and adjacent tissues,
allowing vessels of the cavernous tissue to
fill with blood; the enlarging corpora
compress the venous drainage, producing
further enlargement and turgidity in the
three corpora masses.

Histology of the Female Reproductive System

1. Ovaries
2. Uterine tubes
3. Uterus
4. Cervix
5. Vagina
6. Mammary Gland
Ovaries
 Almond-shaped bodies approximately 3 cm
Primordial Ovarian Follicle
long, 1.5 cm wide, and 1 cm thick covered
 Composed of a simple follicular epithelium.
by simple cuboidal epithelium.
 Cells: Follicular cells
 Major site for oogenesis.

Primary Follicle
 The follicular cells continue to proliferate,
forming a stratified follicular epithelium,

49
 the granulosa, in which the cells  Responsible for preparing the uterus for
communicate through gap junctions. possible implantation during ovulation.
 Cells: Granulosa cells
Corpus Albicans
 Regressed form of corpus luteum.
 Leaves a white scar

Uterine tubes
 Also known as Oviducts or Fallopian tubes
 Supported by ligaments and mesenteries
that allow considerable mobility, each
measure about 10 to 12 cm in length. Each
opens into the peritoneal cavity near the
ovary.
 Responsible for the transportation of egg
cell from the ovary into the uterus.
Vesicular or Antral Follicle
Uterus
 pear-shaped organ with thick, muscular
walls.
 Pear – shaped, dorsoventrally flattened,
hollow, pelvic organ that receives the
conceptus a few days after fertilization and
nourishes and nurtures it throughout its
development.

3 Layers:
a. Perimetrium – outer connective tissue layer
b. Myometrium – thick tunic of highly
vascularized smooth muscle
c. Endometrium – simple columnar epithelial
lining of the uterus

Cervix
 Cylindrical inferior portion of the uterus
whose proximal end projects to the
vagina.
Ovulation
 Hormone-stimulated process by which the a. Ectocervix – potion of cervix that protrudes
oocyte is released from the ovary. into the vagina.
 Ovulation normally occurs midway through b. Endocervix – the rest of the cervix.
the menstrual cycle, that is, around the 14th
day of a typical 28-day cycle. Vagina
 It is a fibromuscular tube that extends from
Fertilization the vestibule of the external genitalia to the
 Union of sperm cell and egg cell. cervix.
 An ovum is viable only for 24 hours after  The vagina has no glands. The epithelial
being ovulated, but it takes 3 – 4 days for surface is kept moist by secretions coming
it to travel from the abdominal cavity into from the cervical and endometrial glands.
the uterus via the oviduct.
External Genitalia
Corpus Luteum
 Cells of the granulosa and thecal layers left  These are structures of the female
in the ovary after ovulation are reproductive system that is external to the
reorganized under the influence of vagina.
luteinizing hormone ( LH ) to form the
endocrine gland called the corpus luteum. 1. Clitoris - Homologous to penis

50
2. Labia majora - Homologous to Scrotum hundreds of millions of sperm a day! Only
3. Labia minora about half of these, however, are likely to
become viable, mature sperm.
Mammary Gland
 Responsible for milk secretion Or lactation Where Sperm Are Produced
in late pregnancy.  Spermatogenesis occurs in the seminiferous
tubules in the testes. Spermatogenesis
Lesson 7: Sperm Anatomy requires high concentrations of testosterone.
Testosterone is secreted by Leydig cells,
which are adjacent to the seminiferous
tubules in the testes.
 Sperm production in the seminiferous
tubules is very sensitive to temperature. This
may be the most important reason the
testes are located outside the body in the
scrotum. The temperature inside the
scrotum is generally about 2 degrees Celsius
 Each normal mature sperm cell has the (almost 4 degrees Fahrenheit) cooler than
structures labeled in this image. The core body temperature. This lower
acrosome is at the front end, just behind temperature is optimal for
the nucleus. The midpiece connects the spermatogenesis. The scrotum regulates its
nucleus to the tail. internal temperature as needed by
contractions of the smooth muscles lining
 A mature sperm cell has several structures the scrotum. When the temperature inside
that help it reach and penetrate an egg. the scrotum becomes too low, the scrotal
These are labeled in the drawing of a muscles contract. The contraction of the
sperm shown in Figure above: muscles pulls the scrotum higher against
a. The head is the part of the sperm that the body, where the temperature is warmer.
contains the nucleus — and not much else. The opposite occurs when the temperature
The nucleus, in turn, contains tightly coiled inside the scrotum becomes too high.
DNA that is the male parent’s contribution
to the genetic makeup of a zygote (if one Events of Spermatogenesis
forms). Each sperm is a haploid cell,  The chart below summarizes the main
containing half the chromosomal cellular events that occur in the process of
complement of a normal, diploid body spermatogenesis. The process begins with a
cell. diploid stem cell called a spermatogonium
b. The front of the head is an area called the (plural, spermatogonia), and involves
acrosome. The acrosome contains several cell divisions. The entire process
enzymes that help the sperm penetrate an takes at least ten weeks to complete,
egg (if it reaches one). including maturation in the epididymis.
c. The midpiece is the part of the sperm
between the head and the flagellum tail.
The midpiece is packed with mitochondria
that produce the energy needed to move
the flagellum.
d. The flagellum (also called the tail) can rotate
like a propeller, allowing the sperm to
“swim” through the female reproductive
tract to reach an egg if one is present.

Spermatogenesis
 The process of producing sperm is known as
spermatogenesis. Spermatogenesis
 Spermatogenesis includes one mitotic
normally starts when a boy reaches puberty,
division and two meiotic divisions.
and it usually continues uninterrupted until
death, although a decrease in sperm
1. A spermatogonium undergoes mitosis to
production generally occurs at older ages. A
produce two diploid cells called primary
young, healthy male may produce

51
 spermatocytes. One of the primary Ejaculation
spermatocytes goes on to produce sperm.  Sperms are released from the body during
The other replenishes the reserve of ejaculation, which typically occurs during
spermatogonia. orgasm. Hundreds of millions of mature
2. The primary spermatocyte undergoes sperm — contained within a small amount
meiosis I to produce two haploid daughter of thick, whitish fluid called semen — are
cells called secondary spermatocytes. propelled from the penis during a normal
3. The secondary spermatocytes rapidly ejaculation.
undergo meiosis II to produce a total of four
haploid daughter cells called spermatids. How Ejaculation Occurs
4. The spermatids begin to form a tail, and  Ejaculation occurs when peristalsis of the
their DNA becomes highly condensed. muscle layers of the vas deferens and other
Unnecessary cytoplasm and organelles are accessory structures propel sperm from the
removed from the cells, and they form a epididymes, where mature sperm are stored.
head, midpiece, and flagellum. The resulting The muscle contractions force the sperm
cells are sperm (spermatozoa). through the vas deferens and the ejaculatory
ducts, and then out of the penis through the
 As shown above are the events of urethra. Due to the peristaltic action of the
spermatogenesis begin near the wall of the muscles, the ejaculation occurs in a series of
seminiferous tubule — where spurts.
spermatogonia are located — and continue
inward toward the lumen of the tubule. The Role of Semen
Sertoli cells extend from the wall of the  As sperms travel through the ejaculatory
seminiferous tubule inward toward the ducts during ejaculation, they mix with
lumen, so they are in contact with secretions from the seminal vesicles, prostate
developing sperm at all stages of gland, and bulbourethral glands to form
spermatogenesis. Sertoli cells play several semen (see photo below). The average
roles in spermatogenesis: amount of semen per ejaculate is about 3.7
mL, which is a little less than a teaspoonful.
1. They secrete endocrine hormones that help Most of this volume of semen consists of
regulate spermatogenesis. glandular secretions, with the hundreds of
2. They secrete substances that initiate meiosis. millions of sperm cells actually contributing
3. They concentrate testosterone (from Leydig relatively little to the total volume
cells), which is needed at high levels to
maintain spermatogenesis.  The secretions in semen are important for
4. They phagocytize the extra cytoplasm that is the survival and motility of sperm. They
shed from developing sperm cells. provide a medium through which sperm
5. They secrete a testicular fluid that helps carry can swim. They also include
sperm into the epididymis. sperm-sustaining substances, such as high
6. They maintain a blood-testis barrier, so concentrations of the sugar fructose, which is
immune system cells cannot reach and the main source of energy for sperm. In
attack the sperm. addition, semen contains many alkaline
substances that help neutralize the acidic
Maturation in the Epididymis environment in the female vagina. This
 Although the sperm produced in the testes protects the DNA in sperm from being
have tails, they are not yet motile (able to denatured by the acid and prolongs the life
“swim”). The non-motile sperms are of sperm in the female reproductive tract.
transported to the epididymis in the
testicular fluid that is secreted by Sertoli Erection
cells with the help of peristaltic contractions.  Besides providing a way for sperm to leave
In the epididymis, the sperms gain motility, the body, the main role of the penis in
so they are capable of swimming up the reproduction is intromission or depositing
female genital tract and reaching an egg. sperm in the vagina of the female
The mature sperms are stored in the reproductive tract. Intromission depends on
epididymis until ejaculation occurs. the ability of the penis to become stiff and
erect, a state referred to as an erection. The
human penis, unlike that of most other

52
 mammals, contains no erectile bone. Instead, Lesson 7: Pregnancy
in order to reach its erect state, it relies
entirely on engorgement with the blood of Egg Production
its columns of spongy tissue. During sexual  At birth, a female’s ovaries contain all the
arousal, the arteries that supply blood to the eggs she will ever produce, which may
penis dilate, allowing more blood to fill the include a million or more eggs. The eggs
spongy tissue. The now-engorged spongy don't start to mature, however, until she
tissue presses against and constricts the veins enters puberty and attains sexual maturity.
that carry blood away from the penis. As a After that, one egg typically matures each
result, more blood enters than leaves the month and is released from an ovary. This
penis, until a constant erectile size is continues until a woman reaches
achieved. menopause (cessation of monthly periods),
typically by age 52. By then, viable eggs
 In addition to sperm, the penis also may be almost depleted, and hormone
transports urine out of the body. These two levels can no longer support the monthly
functions cannot occur simultaneously. cycle. During the reproductive years, which
During an erection, the sphincters that of the two ovaries releases an egg in a given
prevent urine from leaving the bladder are month seems to be a matter of chance.
controlled by centers in the brain so they Occasionally, both ovaries will release an
cannot relax and allow urine to enter the egg at the same time. If both eggs are
urethra. fertilized, the offspring are fraternal twins
(dizygotic, or "two-zygote," twins), and they
Testosterone Production are no more alike genetically than non-twin
 The final major function of the male siblings.
reproductive system is the production of the
male sex hormone testosterone. In mature Oogenesis
males, this occurs mainly in the testes.  The process of producing eggs in the ovaries
Testosterone production is under the of a female fetus is called oogenesis. Eggs are
control of luteinizing hormone (LH) from haploid gametes, and their production
the pituitary gland. LH stimulates Leydig occurs in several steps that involve different
cells in the testes to secrete testosterone. types of cells, as summarized in below,
Oogenesis is completed long before birth. It
Testosterone occurs when diploid germ cells called
 is important for male sexual development at oogonia (singular, oogonium) undergo
puberty. It stimulates maturation of the mitosis. Each such cell division produces two
male reproductive organs, as well as the diploid daughter cells. One is called the
development of secondary male sex primary oocyte, and the other is retained to
characteristics (such as facial hair). help maintain a reserve of oogonia. The
Testosterone is also needed in mature males primary oocyte, in turn, starts to go through
for normal spermatogenesis to be the first cell division of meiosis (meiosis I).
maintained in the testes. Follicle stimulating However, it does not complete meiosis I
hormone (FSH) from the pituitary gland is until much later. Instead, it remains in a
also needed for spermatogenesis to occur, in resting state, nestled within a tiny, immature
part because it helps Sertoli cells in the follicle in the ovary until the female goes
testes concentrate testosterone to high through puberty.
enough levels to maintain sperm
production. Testosterone is also needed for  Formation of a secondary oocyte that may
the proper functioning of the prostate become a zygote begins with mitosis of an
gland. In addition, testosterone plays a role oogonium. This is followed by two meiotic
in erection, allowing sperm to be cell divisions. In humans, the first polar body
deposited within the female reproductive does not undergo the second meiotic
tract. division illustrated here.

Maturation of a Follicle
 Beginning in puberty, about once a month,
one of the follicles in an ovary undergoes
maturation, and an egg is released. As the

53
 follicle matures, it goes through changes in the sperm and allow the surface of the egg
the numbers and types of its cells. The to attach to the surface of the sperm. The
primary oocyte within the follicle also egg can then absorb the sperm, allowing
resumes meiosis. It completes meiosis I, fertilization to occur.
which began long before birth, to form a
secondary oocyte and a smaller cell, called
the first polar body. Both the secondary
oocyte and the first polar body are haploid
cells. The secondary oocyte has most of the
cytoplasm from the primary oocyte and is
much larger than the first polar body, which
soon disintegrates and disappears. The
secondary oocyte begins meiosis II, but only
completes it if the egg is fertilized.

Release of an Egg
 It typically takes 12 to 14 days for a follicle
to mature in an ovary, and for the
secondary oocyte to form. Then, the follicle
bursts open and the ovary ruptures,
releasing the secondary oocyte from the
ovary. This event is called ovulation. The
now-empty follicle starts to change into a  This diagram shows the structures through
structure called a corpus luteum. The which sperm must pass if fertilization of an
expelled secondary oocyte is usually swept egg is to occur. It also shows the event of
into the nearby Fallopian tube by its waving, fertilization, and where fertilization usually
fingerlike fimbriae. occurs.

Uterine Changes If Fertilization Occurs

 While the follicle is maturing in the ovary,  If the secondary oocyte is fertilized by a
the uterus is also undergoing changes to sperm as it passes through the Fallopian tube,
prepare it for an embryo if fertilization the secondary oocyte quickly completes
occurs. For example, the endometrium gets meiosis II, forming a diploid zygote and
thicker and becomes more vascular. Around another polar body. (This second polar
the time of ovulation, the cervix undergoes body, like the first, normally breaks down
changes that help sperm reach the oocyte to and disappears.) The zygote then continues
fertilize it. The cervical canal widens, and the journey through the Fallopian tube to
cervical mucus becomes thinner and more the uterus, during which it undergoes several
alkaline. These changes help promote the mitotic cell divisions. By the time it reaches
passage of sperm from the vagina into the the uterus up to five days after fertilization,
uterus and make the environment more it consists of a ball of cells called a blastocyst.
hospitable to sperm. Within another day or two, the blastocyst
implants itself in the endometrium lining the
Fertilization — or Not uterus, and gestation begins.
 Fertilization of an egg by a sperm normally
occurs in a Fallopian tube, most often in the If Fertilization Does Not Occur
part of the tube that passes above the ovary.  What happens if the secondary oocyte is not
In order for fertilization to occur, sperm fertilized by a sperm as it passes through the
must “swim” from the vagina where they Fallopian tube? It continues on its way to
are deposited, through the cervical canal to the uterus without ever completing meiosis
the uterus, and then through the body of the  II. It is likely to disintegrate within a few
uterus to one of the Fallopian tubes. Once days while still in the Fallopian tube. Any
sperm enters a Fallopian tube, tubular fluids remaining material will be shed from the
help carry them through the tube toward woman’s body during the next menstrual
the secondary oocyte at the other end. The period.
secondary oocyte also functions to promote
fertilization. It releases molecules that guide

54
Pregnancy experience tender breasts, increased appetite,
 Pregnancy is the carrying of one or more and more frequent urination. Many women
offspring from fertilization until birth. This is also experience nausea and vomiting in the
one of the major functions of the female first trimester. This is often called “morning
reproductive system. It involves virtually sickness,” because it commonly occurs in the
every other body system including the morning, but it may occur at any time of
cardiovascular, urinary, and respiratory day. Some women may lose weight during
systems, to name just three. The maternal the first trimester because of morning
organism plays a critical role in the sickness.
development of the offspring. She must
provide all the nutrients and other Second Trimester
substances needed for normal growth and  The second trimester occurs during weeks 13
development of the offspring, and she must to 28 of pregnancy. A pregnant woman
also remove the wastes excreted by the may feel more energized during this
offspring. Most nutrients are needed in trimester. If she experienced nausea and
greater amounts by a pregnant woman to vomiting during the first trimester, these
meet fetal needs, but some are especially symptoms often subside during the second
important, including folic acid, calcium, iron, trimester. Weight gain starts occurring
and omega-3 fatty acids. A healthy diet, during this trimester, as well. By about week
along with prenatal vitamin supplements, is 20, the fetus is getting large enough that the
recommended for the best pregnancy mother can feel its movements. The photo
outcome. A pregnant woman should also on the left on Figure 22.8.422.8.4 shows a
avoid ingesting substances (such as alcohol) pregnant woman at week 26, toward the
that can damage the developing offspring, end of the second trimester.
especially early in the pregnancy when all of
the major organs and organ systems are Third Trimester
forming.  The third trimester occurs during weeks 29
 When counted from the first day of the last through birth (at about 40 weeks). During
menstrual period, the average duration of this trimester, the uterus expands rapidly,
pregnancy is about 40 weeks (38 weeks making up a larger and larger portion of the
when counted from the time of fertilization), woman's abdomen. Weight gain is also
but a pregnancy that lasts between 37 and more rapid. During the third trimester, the
42 weeks is still considered within the movements of the fetus become stronger
normal range. From the point of view of the and more frequent, and they may become
maternal organism, the total duration of disruptive to the mother. As the fetus grows
pregnancy is typically divided into three larger, its weight and the space it takes up
periods, called trimesters, each of which lasts may lead to symptoms in the mother such as
about three months. This division of the back pain, swelling of the lower extremities,
total period of gestation is useful for more frequent urination, varicose veins, and
summarizing the typical changes a woman heartburn. By the end of the third trimester,
can expect during pregnancy. From the the woman's abdomen often will transform
point of view of the developing offspring, in shape as it drops, due to the fetus turning
however, the major divisions are different. to a downward position before birth so its
They are the embryonic and fetal stages. The head rests on the cervix. This relieves
offspring is called an embryo from the time pressure on the upper abdomen, but reduces
it implants in the uterus through the first bladder capacity and increases pressure on
eight weeks of life. After that, it is called a the pelvic floor and rectum.
fetus for the duration of the pregnancy.
Childbirth
First Trimester  Near the time of birth, the amniotic sac — a
 The first trimester begins at the time of fluid-filled membrane that encloses the fetus
fertilization and lasts for the next 12 weeks. within the uterus — breaks in a gush of fluid.
Even before she knows she is pregnant, a This is commonly called “breaking water.”
woman in the first trimester is likely to Labor usually begins within a day of this
experience signs and symptoms of event, although it may begin prior to it.
pregnancy. She may notice a missed Labor is the general term for the process of
menstrual period, and she may also childbirth in which regular uterine

55
 contractions push the fetus and placenta out Breastfeeding
of the body. Labor can be divided into three  Although the breasts are not classified as
stages, dilation, birth, and after birth. organs of the reproductive system, they
nonetheless may play an important role in
1. During the dilation stage of labor, uterine reproduction. The physiological function of
contractions begin and become increasingly the female breast is lactation or the
frequent and intense. The contractions push the production of breastmilk to feed an infant.
baby’s head (most often) against the cervix, This function is illustrated in the figure
causing the cervical canal to dilate, or become below. Besides nutrients, breastmilk
wider. This lasts until the cervical canal has provides hormones, antibodies, and other
dilated to about 10 cm (3.9 in.) in width, which substances that help ensure a healthy start
may take 12 to 20 hours — or even longer. The after birth.
cervical canal must be dilated to this extent in  As shown the correct way for an infant to
order for the baby’s head to fit through it. suck the breast to stimulate the letdown of
milk from the mammary glands. The
2. During birth, the baby descends (usually letdown of milk when an infant sucks at the
headfirst) through the cervical canal and vagina, breast is one of the few examples of positive
and into the world outside. This is the stage when feedback in the human organism. Sucking
the mother generally starts bearing down during causes a release from the posterior pituitary
the contractions to help push out the fetus. This gland of the hypothalamic hormone
stage may last from about 20 minutes to two oxytocin. Oxytocin, in turn, causes milk to
hours or more. Usually, within a minute or less of flow from the alveoli in the breasts where
birth, the umbilical cord is cut, so the baby is no milk is produced, through the milk ducts,
longer connected to the placenta. and into the milk sacs behind the areola.
You can trace this route of milk through the
3. During the afterbirth stage, the placenta is breast in the figure below. The baby can
delivered. This stage may last from a few minutes suck the milk out of the sacs through the
to a half hour. nipple, where they converge. The release of
milk stimulates the baby to continue sucking,
which in turn keeps the milk flowing.

56
Female Sex Hormones
 Female reproduction could not occur
without sex hormones released by the
ovaries. These hormones include estrogen
and progesterone.

Estrogen
 Before birth, estrogen is released by the
gonads in female fetuses and leads to the
development of female reproductive organs.
At puberty, estrogen levels rise and are
responsible for sexual maturation, and for
the development of female secondary sex
characteristics (such as breasts). Estrogen is
also needed to help regulate the menstrual
cycle and ovulation throughout a woman’s
reproductive years. Estrogen is produced
primarily by follicular cells in the ovaries.
During pregnancy, estrogen is also produced
by the placenta. There are actually three
forms of estrogen in the human female:
estradiol, estriol, and estrone.

1. Estradiol is the predominant form of estrogen

during the reproductive years. It is also the most
potent form of estrogen.
2. Estriol is the predominant form of estrogen
during pregnancy. It is also the weakest form of
estrogen.
3. Estrone is the predominant form of estrogen
in post-menopausal women. It is intermediate in
strength between the other two forms of
estrogen.

Progesterone
 Progesterone stands for “pro-gestational
hormone.” It is synthesized and secreted
primarily by the corpus luteum in the ovary.
Progesterone plays many physiological roles
but is best known for its role during
pregnancy. In fact, it is sometimes called the
“hormone of pregnancy.” Among other
functions, progesterone prepares the uterus
for pregnancy each month by building up
the uterine lining. If pregnancy occurs,
progesterone helps maintain the pregnancy
in a number of ways, such as decreasing the
maternal immune response to the
genetically different embryo and decreasing
the ability of uterine muscle tissue to
contract. Progesterone also prepares the
mammary glands for lactation during
pregnancy, and withdrawal of progesterone
after birth is one of the triggers of milk
production.

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