Chapter 10: BLOOD in a healthy adult

 Blood makes up 8 percent of body weight

Functions of the Blood

Distribution
Plasma
Blood transports everything that must be carried from
 90 percent water
one place to another, such as: Nutrients, Wastes,
Hormones, Body heat  Straw-colored fluid

Regulation  Includes many dissolved substances

Maintaining appropriate body temperature
 Nutrients
Maintaining normal pH in body tissues
 Salts (electrolytes)
Maintaining adequate fluid volume in the circulatory
 Respiratory gases
system
 Hormones
Protection  Plasma proteins
Preventing blood loss
 Waste products
Preventing infection

Components of Blood
Plasma proteins
Blood is the only fluid tissue, a type of connective tissue,
in the human body  Most abundant solutes in plasma
Formed elements (living cells)
Plasma (nonliving fluid matrix)  Most are made by the liver

 Include:

When blood is separated:  Albumin—an important blood buffer and contributes to

Erythrocytes sink to the bottom (45 percent of blood, a osmotic pressure
percentage known as the hematocrit)  Clotting proteins—help to stem blood loss when a
Buffy coat contains leukocytes and platelets (less than 1 blood vessel is injured
percent of blood)  Antibodies—help protect the body from pathogens
Buffy coat is a thin, whitish layer between the
erythrocytes and plasma
Plasma rises to the top (55 percent of blood) Blood composition varies as cells exchange substances
with the blood

Physical Characteristics and Volume  Liver makes more proteins when levels drop

 Blood characteristics  Respiratory and urinary systems restore blood pH to

 Sticky, opaque fluid normal when blood becomes too acidic or alkaline

 Heavier and thicker than water  Plasma helps distribute body heat

Color range Formed Elements

 Oxygen-rich blood is scarlet red
 Oxygen-poor blood is dull red or purple  Erythrocytes - Red blood cells (RBCs)
 Metallic, salty taste
 Leukocytes - White blood cells (WBCs)
 Blood pH is slightly alkaline, between 7.35 and 7.45
 Blood temperature is slightly higher than body  Platelets - Cell fragments
temperature, at 38ºC or 100.4ºF

Homeostatic imbalance of RBCs

 Blood volume
 About 5–6 liters, or about 6 quarts, of blood are found
 Anemia is a decrease in the oxygen-carrying ability of  Include neutrophils, eosinophils, and basophils
the blood due to:
 Agranulocytes
 Lower-than-normal number of RBCs
 Abnormal or deficient hemoglobin content in the RBCs  Lack visible cytoplasmic granules
 Sickle cell anemia (SCA) results from abnormally shaped
hemoglobin  Nuclei are spherical, oval, or kidney-shaped

 Include lymphocytes and monocytes

Polcythemia

 Disorder resulting from excessive or abnormal increase List of the WBCs, from most to least abundant
of RBCs due to:  Neutrophils (Never)
 Bone marrow cancer (polycythemia vera)  Lymphocytes (Let)
 Life at higher altitudes (secondary polycythemia)  Monocytes (Monkeys)
 Increase in RBCs slows blood flow and increases blood  Eosinophils (Eat)
viscosity
 Basophils (Bananas)

Leukocytes (white blood cells, or WBCs)

Granulocytes
 Crucial in body’s defense against disease
 Neutrophils
 Complete cells, with nucleus and organelles
 Most numerous WBC
 Able to move into and out of blood vessels (diapedesis)
 Respond to chemicals released by damaged tissues  Multilobed nucleus
(known as positive chemotaxis)  Cytoplasm stains pink and contains fine granules
 Move by amoeboid motion
 Function as phagocytes at active sites of infection
 4,800 to 10,800 WBCs per mm3 of blood
 Numbers increase during infection

Leukocytosis  3,000–7,000 neutrophils per mm3 of blood (40–70

percent of WBCs)
 WBC count above 11,000 cells per mm3 of blood

 Generally indicates an infection

Eosinophils
 Leukopenia
 Nucleus stains blue-red
 Abnormally low WBC count
 Brick-red cytoplasmic granules
 Commonly caused by certain drugs, such as
corticosteroids and anticancer agents  Function is to kill parasitic worms and play a role in
allergy attacks
 Leukemia
 100–400 eosinophils per mm3 of blood (1–4 percent of
 Bone marrow becomes cancerous WBCs)
 Numerous immature WBC are produced

Basophils
Types of leukocytes  Rarest of the WBCs
 Granulocytes  Large histamine-containing granules that stain dark
 Granules in their cytoplasm can be stained blue

 Possess lobed nuclei  Contain heparin (anticoagulant)

 20–50 basophils per mm3 of blood (0–1 percent of  RBCs wear out in 100 to 120 days
WBCs)
 When worn out, RBCs are eliminated by phagocytes in
the spleen or liver
 Lost cells are replaced by division of hemocytoblasts in
Agranulocytes
the red bone marrow
 Lymphocytes
Rate of RBC production is controlled by a hormone called
 Large, dark purple nucleus erythropoietin
 Kidneys produce most erythropoietin as a response to
 Slightly larger than RBCs reduced oxygen levels in the blood
 Reside in lymphatic tissues  Homeostasis is maintained by negative feedback from
blood oxygen levels
 Play a role in immune response

 1,500–3,000 lymphocytes per mm3 of blood (20–45 Formation of White Blood Cells and Platelets
percent of WBCs)
 WBC and platelet production is controlled by hormones
 Colony stimulating factors (CSFs) and interleukins
Monocytes prompt bone marrow to generate leukocytes
 Thrombopoietin stimulates production of platelets
 Largest of the white blood cells from megakaryocytes
 Distinctive U- or kidney-shaped nucleus

 Function as macrophages when they migrate into Hemostasis

tissues
 Hemostasis is the process of stopping the bleeding that
 Important in fighting chronic infection results from a break in a blood vessel
 Hemostasis involves three phases
 100–700 monocytes per mm3 of blood (4–8 percent of
WBCs)
1. Vascular spasms

2. Platelet plug formation

Platelets
3. Coagulation (blood clotting)
 Fragments of megakaryocytes (multinucleate cells)

 Needed for the clotting process

Step 1: vascular spasms
 Normal platelet count is 300,000 platelets per mm3 of
blood  Immediate response to blood vessel injury

 Vasoconstriction causes blood vessel to spasm

Hematopoiesis is the process of blood cell formation
 Spasms narrow the blood vessel, decreasing blood loss
 Occurs in red bone marrow (myeloid tissue)
 Factors:
 All blood cells are derived from a common stem cell
(hemocytoblast)  Direct injury to vascular smooth muscle

 Hemocytoblasts form two types of descendants  Chemicals released by endothelial cells

 Lymphoid stem cell, which produces lymphocytes  Platelets

 Myeloid stem cell, which can produce all other formed  Reflexes initiated by local pain receptors
elements
Step 2: platelet plug formation
Since RBCs are anucleate, they are unable to divide,  Collagen fibers are exposed by a break in a blood vessel
grow, or synthesize proteins  Platelets become ―sticky‖ and cling to fibers
 Anchored platelets release chemicals to attract more  Even normal movements can cause bleeding from small
platelets blood vessels that require platelets for clotting
 Platelets pile up to form a platelet plug (white
 Evidenced by petechiae (small purplish blotches on the
thrombus)
skin)

Step 3: coagulation or blood clotting

Hemophilia
 Injured tissues release tissue factor (TF)
 Hereditary bleeding disorder
 PF3 (a phospholipid) interacts with TF, blood protein
 Normal clotting factors are missing
clotting factors, and calcium ions to trigger a clotting
cascade  Minor tissue damage can cause life-threatening
prolonged bleeding
 Prothrombin activator converts prothrombin to
thrombin (an enzyme)

Thrombin joins fibrinogen proteins into hairlike Blood Groups and Transfusions
molecules of insoluble fibrin
 Fibrin forms a meshwork (the basis for a clot)  Large losses of blood have serious consequences
 Within the hour, serum is squeezed from the clot as it  Loss of 15 to 30 percent causes weakness
retracts  Loss of over 30 percent causes shock, which can be
 Serum is plasma minus clotting proteins fatal
 Blood transfusions are given for substantial blood loss,
to treat severe anemia, or for thrombocytopenia
Hemostasis

 Blood usually clots within 3 to 6 minutes

Human Blood Groups
 The clot remains as endothelium regenerates
 Blood contains genetically determined proteins known
 The clot is broken down after tissue repair as antigens

 Antigens are substances that the body recognizes as

foreign and that the immune system may attack
Disorders of Hemostasis
 Most antigens are foreign proteins
 Undesirable clotting  We tolerate our own ―self‖ antigens
 Antibodies are the ―recognizers‖ that bind foreign
 Thrombus
antigens
 A clot in an unbroken blood vessel  Blood is ―typed‖ by using antibodies that will cause
blood with certain proteins to clump (agglutination) and
 Can be deadly in areas such as the lungs lyse
 Embolus

 A thrombus that breaks away and floats freely in the There are over 30 common red blood cell antigens
bloodstream  The most vigorous transfusion reactions are caused by
ABO and Rh blood group antigens
 Can later clog vessels in critical areas such as the brain

ABO blood group

Bleeding disorders
 Blood types are based on the presence or absence of
 Thrombocytopenia two antigens
 Insufficient number of circulating platelets 1. Type A

 Arises from any condition that suppresses the bone 2. Type B

marrow
 Presence of both antigens A and B is called type AB
 Presence of antigen A is called type A RBCs by the recipient’s serum, and vice versa

 Presence of antigen B is called type B

Developmental Aspects of Blood
 Lack of both antigens A and B is called type O
 Sites of blood cell formation
 Type AB can receive A, B, AB, and O blood
 The fetal liver and spleen are early sites of blood cell
 Type AB is the ―universal recipient‖
formation
 Type B can receive B and O blood  Bone marrow takes over hematopoiesis by the seventh
month
 Type A can receive A and O blood Congenital blood defects include various types of
 Type O can receive O blood hemolytic anemias and hemophilia

 Type O is the ―universal donor‖

 Incompatibility between maternal and fetal blood can
Rh blood group result in fetal cyanosis, resulting from destruction of fetal
blood cells
 Named for the eight Rh antigens (agglutinogen D)
 Fetal hemoglobin differs from hemoglobin produced
 Most Americans are Rh+ after birth
(Rh-positive), meaning they carry the Rh antigen  Physiologic jaundice occurs in infants when the liver
 If an Rh– (Rh-negative) person receives Rh+ blood: cannot rid the body of hemoglobin breakdown products
fast enough
 The immune system becomes sensitized and begins
producing antibodies; hemolysis does not occur, because
as it takes time to produce antibodies Leukemias are most common in the very young and very
 Second, and subsequent, transfusions involve old
antibodies attacking donor’s Rh+ RBCs, and hemolysis  Older adults are also at risk for anemia and clotting
occurs (rupture of RBCs) disorders

Rh-related problem during pregnancy The Cardiovascular System

 Danger occurs only when the mother is Rh–, the father - closed system of heart and blood vessels
is Rh+, and the child inherits the Rh+factor  Heart pumps blood
 RhoGAM shot can prevent buildup of anti-Rh+  Blood vessels allow blood to circulate
antibodies in mother’s blood. The mismatch of an Rh– - functions of the cardiovascular system
mother carrying an Rh+ baby can cause problems for the
unborn child  Transport oxygen, nutrients, cell wastes,
 The first pregnancy usually proceeds without problems; hormones to and from cells
the immune system is sensitized after the first pregnancy Anatomy of the Heart
 In a second pregnancy, the mother’s immune system
produces antibodies to attack the Rh+ blood (hemolytic - size of a human fist
disease of the newborn)
- located in the Thoracic Cavity, between the Lungs in the
inferior mediastinum

Blood samples are mixed with anti-A and anti-B serum - orientation:

 Agglutination or the lack of agglutination leads to  Apex is directed toward left hip and rests on
identification of blood type diaphragm, base points to right shoulder
 Typing for ABO and Rh factors is done in the same
Coverings of the Heart
manner
 Cross matching—testing for agglutination of donor  Pericardium – a double-walled sac
  Fibrous pericardium – loose and  Interatrial Septum
superficial
- separates the 2 atria longitudinally
 Serous membrane is deep to the FP and
composed of 2 layers:  Interventricular Septum
1. Parietal Pericardium: outside layer that lines the
inner surface of the FP - separates the 2 ventricles longitudinally
2. Visceral Pericardium: next to heart; also known  Heart functions as a Double Pump:
as Epicardium  Arteries: carry blood away from the heart
 Serous fluid – fills the space between layers of  Veins: carry blood toward the heart
Pericardium called Pericardial Cavity  Double Pump:
Functions of the Pericardium:  Pulmonary Circuit Pump: works the Right side
 Systemic Circuit Pump: works the Left side
- keeps the heart contained within the chest cavity
 Pulmonary Circulation:
- prevents heart from over expanding when blood
volume increases - blood flows from right side of the heart to the lungs and
back to the left side of the heart
- limits heart motion
 Blood is pumped out through the pulmonary
- reduces friction between heart and surrounding tissues
trunk, which splits into pulmonary arteries and
- protects heart from infection takes oxygen-poor blood to lungs
 Oxygen –rich blood returns to the heart from the
Walls of the Heart
lungs via pulmonary veins
1. Epicardium (Pericardium)  Systemic Circulation

- outside layer - oxygen-rich blood returned to the left side of the heart
is pumped out into the aorta
2. Myocardium
 Blood circulates to systemic arteries and to all
- middlea layer, mostly cardiac muscle body tissues
- layer that contracts  Left ventricle has thicker walls because it pumps
blood to the body through systemic circuit
3. Endocardium  Oxygen-poor blood returns to the right atrium via
- inner layer known as endothelium systemic veins, which empty blood into the
superior or inferior vena cava
- lines the inner heart chambers, covers heart valve,
continuous with endothelium of large blood vessels Heart Valves

Four Chambers of the Heart - allow blood to flow in 1 direction to prevent backflow

 Atria (right and left) - open and close in response to pressure

- receiving chambers  Atrioventricular (AV) Valves - between atria and

ventricles
- assist with filling the ventricles
1. Left AV valve – Bicuspid (mitral) valve
- blood enters under low pressure
2. Right AV – Tricuspid valve
 Ventricles (left and right)
 Anchors the cusps in pace by chordae tendinae
- discharging chambers to open the walls of ventricles
 Open during heart relaxation, when blood
- thick-walled pumps of the heart
passively fills the chambers
- during contraction, blood is propelled into  Closed during ventricular contraction
circulation
 Semilunar Valves – between ventricle and artery
Associated Great Vessels
- Pulmonary and Aortic semilunar valves
- closed during heart relaxation - ventricles contract, blood is ejected from the
heart
- open during ventricular contraction
 Homeostatic imbalance
Cardiac Circulation  Heart block – damage to AV node causes ventricles
to beat at their own rate (slower) some or all of the
- blood I the heart chambers does not nourish the time
myocardium  Ischemia – lack of adequate blood supply to the
- the heart has its own nourishing circulatory system heart muscles
 Fibrillation – rapid, uncoordinated quivering of the
 Coronary arteries – branch from aorta to supply ventricles; makes heart unable to pump blood, Major
heart muscle with oxygenated blood cause of death from heart attacks in adult
 Cardiac veins – drain the myocardium o blood  Tachycardia – rapid heart rate, over 100 bpm
 Coronary sinus – large vein on the posterior of  Bradycardia – slow heart rate, less than 60 bpm
the heart; receives blood from cardiac veins  Cardiac cycle and heart sounds
- blood empties into the right atrium via the coronary - Cardiac Cycle: refers to one complete heartbeat, in
sinus which both atria and ventricles contract then relax
Physiology of the Heart  Systole = contraction
 Intrinsic conduction system (nodal system) of the  Diastole = relaxation
heart: - Average heart rate is approximately 75 bpm
- built into the heart tissue and sets its basic rhythm - Cardiac cycle length is normally 0.8 second
- composed of specialized tissue  5 Events of the Cardiac cycle
- causes heart muscle depolarization in one direction 1. Atrial Diastole (Ventricular filling)
only (atria to ventricles); heart rate = 75bpm
 Heart is relaxed
- cardiac muscle contracts spontaneously and  Pressure in heart is low
independently of nerve impulses  AV valves are open
- spontaneous contractions occur in a regular and  Blood flows passively into the atria and into
continuous way: ventricles
 Semilunar valves are closed
 Atrial cells beat 60 times per minute
 Ventricular cells beat 20-40 times per minute 2. Atrial systole

Components include:  Ventricles remain in diastole

 Atria contract
 Sinoatrial (SA) Node  Blood is forced into the ventricles to complete
- located in the right atrium ventricular filling
- serves as the hearts pacemaker
 Atrioventricular (AV) Node 3. Isovolumetric contraction
- at the junction of the atria and ventricles  Atrial systole ends; ventricular systole begins
 Atrioventricular (AV) Bundle (bundle of his)  Intraventricular pressure rises
- spread within the ventricle wall muscles  AV valves close
Physiology of the heart  For a moment, the ventricles are completely
closed chambers
 Intrinsic conduction system of the heart
pathway 4. Ventricular systole
- SA node starts each heartbeat  Ventricles continue to contract
- impulse spreads through the atria to the AV  Intraventricular pressure now surpasses the
node then AV contract pressure in the major arteries leaving the heart
- at the AV node, the impulse is delayed briefly  Semilunar valves open
- impulse travels through the AV bundle, bundle  Blood is ejected from the ventricles
branches, and purkinje fibers
  Atria are relaxed and filling with blood 1. Neural (ANS) controls

5. Isovolumetric relaxation  Sympathetic nervous system speeds heart rare

 Parasympathetic nervous system, primarily
 Ventricular diastole begins
vagus nerve fibers, slow and steady the heart
 Pressure falls below that in the major arteries
rate
 Semilunar valves close
 For another moment, the ventricles are 2. Hormones and Ions
completely closed chambers
 Epinephrine and thyroxine speed heart rate
 When atrial pressure increases above
 Excess or lack of calcium, sodium, and potassium
intraventricular
ions also modify heart activity
 Heart sounds
 Lub – longer, louder heart sound caused by the 3. Physical factors
closing of the AV valves
 Dub – short, sharp heart sounds caused by the  Age, gender, exercise, body temperature
closing of the semilunar valves at the end of influence heart rate
ventricular systole  Resting heart rate in fetus (140 – 160 bpm)
 Heart murmurs – sounds during heartbeat cycle  Ave. adult females (72 – 80 bpm)
(whooshing or swishing) made by turbulent  Ave. adult males (64 – 72 bpm)
blood in or near your heart
 Not a disease but may/can indicate an
underlying heart problem Blood Vessels
 Cardiac Output (CO) - form a closed vascular system that transports blood to
 Amount of blood pumped by each side the tissues and back to the heart
(ventricle) of the heart in 1 minute
 Stroke Volume (SV)  Arteries and Arterioles
 Volume of blood pumped by each - vessels that carry blood away from the heart
ventricle in one contraction (each  Capillary beds
heartbeat) -vessels that play a role in exchanges between
 About 70 ml of blood is pumped out of tissues and blood
the left ventricle with each heartbeat  Venules and Veins
 Heart Rate (HR) - vessels tht return blood to the heart
 Typically 75 bpm
Microscopic Anatomy of Blood Vessels
 Examples:
- 3 layers (tunics) in blood vessels (except the capillaries)
CO = HR (75 beats/min) x SV (70 ml/beat)
 Tunica Intima
CO = 5250 ml/min =5.25 L/min
- forms a friction-reducing lining
 Regulation of Stroke Volume - Endothelium
 Tunica media
- 60% of blood in ventricles (about 70 ml/ 2 ounces) is - smooth muscle and elastic tissue
pumped with each heartbeat - controlled by sympathetic nervous system
- Starling`s Law of the heart:  Tunica externa
 The critical factor controlling SV is how much - mostly fibrous connective tissue
cardiac muscle is stretched - supports and protects the vessel
 The more cardiac muscle is stretched, the  Structural differences in arteries, veins and capillaries
stronger the contraction  Arteries
- have heavier, stronger, stretchier tunica media
- Venous return: the important factor influencing the than veins to withstand changes in pressure
stretch of heart muscle  Veins
- Muscular pump; plays a major role in increasing venous - have thinner tunica media that arteries and
return operate under low pressure
- have valves to prevent backflow of blood
 Factors modifying basic heart rate - Lumen of veins is larger than that of arteries
 - Skeletal muscle milks blood in veins toward  Other branches of the thoracic aorta (not illustrated)
heart supply the:
 Capillaries
 Lungs (bronchial arteries)
- only one cell layer thick (tunica intima)
- allow for exchanges between blood and tissue  Esophagus (esophageal arteries)
- form networks called capillary beds that consist
of: Vascular shunt + True capillaries  Diaphragm (phrenic arteries)
- blood flow through capillary bed is also known
as microcirculation
 True Capillaries Arterial branches of the abdominal aorta
- branch off a terminal arteriole  Celiac trunk is the first branch of the abdominal aorta.
- empty directly into a postcapillary venule
- entrances to capillary beds are guarded by Three branches are:
precapillary sphincters
1. Left gastric artery (stomach)

2. Splenic artery (spleen)

Major arteries of systemic circulation
3. Common hepatic artery (liver)
Aorta - Largest artery in the body
 Superior mesenteric artery supplies most of the small
- Leaves from the left ventricle of the heart intestine and first half of the large intestine

Regions:

- Ascending aorta—leaves the left ventricle  Left and right renal arteries (kidney)

- Aortic arch—arches to the left  Left and right gonadal arteries

- Thoracic aorta—travels downward through the thorax  Ovarian arteries in females serve the ovaries

- Abdominal aorta—passes through the diaphragm into  Testicular arteries in males serve the testes
the abdominopelvic cavity.
 Lumbar arteries serve muscles of the abdomen and
Arterial branches of the ascending aorta trunk

 Right and left coronary arteries serve the heart

Arterial branches of the aortic arch
 Inferior mesenteric artery serves the second half of the
 Brachiocephalic trunk splits into the: large intestine

 Right common carotid artery  Left and right common iliac arteries are the final
branches of the aorta
 Right subclavian artery
 Internal iliac arteries serve the pelvic organs
 Left common carotid artery splits into the:
 External iliac arteries enter the thigh → femoral artery
 Left internal and external carotid arteries → popliteal artery → anterior and posterior tibial arteries
 Left subclavian artery branches into the:

 Vertebral artery Major veins of systemic circulation

 In the axilla, the subclavian artery becomes the axillary  Superior vena cava and inferior vena cava enter the
artery → brachial artery → radial and ulnar arteries right atrium of the heart
Arterial branches of the thoracic aorta  Superior vena cava drains the head and arms
 Intercostal arteries supply the muscles of the thorax  Inferior vena cava drains the lower body
wall

Veins draining into the superior vena cava

 Radial and ulnar veins → brachial vein → axillary vein  Hepatic portal vein drains the digestive organs and
travels through the liver before it enters systemic
 Cephalic vein drains the lateral aspect of the arm and
circulation
empties into the axillary vein
 Left and right hepatic veins drain the liver
 Basilic vein drains the medial aspect of the arm and
empties into the brachial vein
Arterial supply of the brain and the circle of Willis
 Basilic and cephalic veins are joined at the median
cubital vein (elbow area)  Internal carotid arteries divide into:

 Anterior and middle cerebral arteries

 Subclavian vein receives:  These arteries supply most of the cerebrum

 Venous blood from the arm via the axillary vein  Vertebral arteries join once within the skull to form the
basilar artery
 Venous blood from skin and muscles via external
jugular vein  Basilar artery serves the brain stem and cerebellum

 Vertebral vein drains the posterior part of the head

Posterior cerebral arteries form from the division of the
 Internal jugular vein drains the dural sinuses of the
basilar artery
brain
 These arteries supply the posterior cerebrum
Anterior and posterior blood supplies are united by
small communicating arterial branches
Left and right brachiocephalic veins receive venous blood  Result—complete circle of connecting blood vessels
from the: called cerebral arterial circle, or circle of Willis
 Subclavian veins

 Vertebral veins Hepatic portal circulation is formed by veins draining the

digestive organs, which empty into the hepatic portal
 Internal jugular veins vein
 Brachiocephalic veins join to form the superior vena  Digestive organs
cava → right atrium of heart  Spleen
 Pancreas
 Azygos vein drains the thorax  Hepatic portal vein carries this blood to the liver, where
it is processed before returning to systemic circulation.

Veins draining into the inferior vena cava

Blood pressure
 Anterior and posterior tibial veins and fibial veins drain
 The pressure the blood exerts against the inner walls of
the legs
the blood vessels
 Posterior tibial vein → popliteal vein → femoral vein →
 The force that causes blood to continue to flow in the
external iliac vein
blood vessels
 Great saphenous veins (longest veins of the body)
receive superficial drainage of the legs
Blood pressure gradient
 Each common iliac vein (left and right) is formed by the
 When the ventricles contract:
union of the internal and external iliac vein on its own
 Blood is forced into elastic arteries close to the heart
side.
 Blood flows along a descending pressure gradient
 Pressure decreases in blood vessels as distance from
Right gonadal vein drains the right ovary in females and the heart increases
right testicle in males  Pressure is high in the arteries, lower in the capillaries,
 Left gonadal vein empties into the left renal vein and lowest in the veins
 Left and right renal veins drain the kidneys
Measuring blood pressure
  Various substances can cause increases or decreases in
 Two arterial blood pressures are measured blood pressure
 Systolic—pressure in the arteries at the peak of
 Epinephrine increases heart rate and blood pressure
ventricular contraction
 Diastolic—pressure when ventricles relax
 Expressed as systolic pressure over diastolic pressure in Diet
millimeters of mercury (mm Hg)
 For example, 120/80 mm Hg  Commonly believed that a diet low in salt, saturated
 Auscultatory method is an indirect method of fats, and cholesterol prevents hypertension (high blood
measuring systemic arterial blood pressure, most often in pressure)
the brachial artery

Variations in blood pressure

Effects of various factors on blood pressure  Normal human range is variable
 Arterial blood pressure (BP) is directly related to cardiac  Systolic pressure ranges from 110 to 140 mm Hg
output and peripheral resistance
 Diastolic pressure ranges from 70 to 80 mm Hg
 Cardiac output (CO; the amount of blood pumped out
of the left ventricle per minute) Hypotension (low blood pressure)
 Low systolic (below 100 mm Hg)
 Peripheral resistance (PR; the amount of friction blood  Often associated with illness
encounters as it flows through vessels)  Acute hypotension is a warning sign for circulatory
BP = CO × PR shock
 Hypertension (high blood pressure)

Neural factors: the autonomic nervous system  Sustained elevated arterial pressure of 140/90 mm Hg

 Parasympathetic nervous system has little to no effect  Warns of increased peripheral resistance
on blood pressure

 Sympathetic nervous system promotes vasoconstriction Capillary exchange of gases and nutrients
(narrowing of vessels), which increases blood pressure
 Interstitial fluid (tissue fluid) is found between cells

 Substances move to and from the blood and tissue cells

Renal factors: the kidneys through capillary walls
 Kidneys regulate blood pressure by altering blood  Exchange is due to concentration gradients
volume
 Oxygen and nutrients leave the blood and move into
 If blood pressure is too high, the kidneys release water tissue cells
in the urine
 Carbon dioxide and other wastes exit tissue cells and
 If blood pressure is too low, the kidneys release renin enter the blood
to trigger formation of angiotensin II, a vasoconstrictor
 Substances take various routes entering or leaving the
 Angiotensin II stimulates release of aldosterone, which blood
enhances sodium (and water) reabsorption by kidneys

1. Direct diffusion through membranes

Temperature
2. Diffusion through intercellular clefts (gaps between
 Heat has a vasodilating effect cells in the capillary wall)
 Cold has a vasoconstricting effect 3. Diffusion through pores of fenestrated capillaries
4. Transport via vesicles
 Chemicals
Fluid movement out of or into a capillary depends on the  Hypertension resulting from loss of elasticity of vessels
difference between the two pressures  Coronary artery disease resulting from fatty, calcified
deposits in the vessels
1. Blood pressure forces fluid and solutes out of
capillaries
2. Osmotic pressure draws fluid into capillaries Chapter 13: The Respiratory System

Blood pressure is higher than osmotic pressure at the Organs of the Respiratory System
arterial end of the capillary bed
 Nose
 Blood pressure is lower than osmotic pressure at the
 Pharynx
venous end of the capillary bed
 Thus, fluid moves out of the capillary at the beginning  Larynx
of the bed and is reclaimed at the opposite (venule) end
 Trachea

 Bronchi

 Lungs—alveoli (terminal sacs)

Developmental Aspects of the Cardiovascular System
 In an embryo
 The heart develops as a simple tube and pumps blood Functional Anatomy of the Respiratory System
by week 4 of pregnancy  Gas exchanges between the blood and external
 The heart becomes a four-chambered organ capable of environment occur only in the alveoli of the lungs
acting as a double pump over the next 3 weeks  Upper respiratory tract includes passageways from the
nose to larynx
Umbilical cord  Lower respiratory tract includes passageways from
 Carries nutrients and oxygen from maternal blood to trachea to alveoli
fetal blood  Passageways to the lungs purify, humidify, and warm
 Fetal wastes move from fetal blood to maternal blood the incoming air
 Houses:
 One umbilical vein, which carries nutrient- and
oxygenrich blood to the fetus The Nose
 Two umbilical arteries, which carry wastes and carbon  The only externally visible part of the respiratory
dioxide–rich blood from the fetus to placenta system
 Nostrils (nares) are the route through which air enters
Shunts bypassing the lungs and liver are present in a the nose
fetus  Nasal cavity is the interior of the nose
 Blood flow bypasses the liver through the ductus  Nasal septum divides the nasal cavity
venosus and enters the inferior vena cava → right atrium
of heart
 Blood flow bypasses the lungs
Olfactory receptors are located in the mucosa on the
 Blood entering right atrium is shunted directly into left
superior surface
atrium through foramen ovale (becomes fossa ovalis at
 The rest of the cavity is lined with respiratory mucosa,
or after birth)
which
 Ductus arteriosus connects aorta and pulmonary trunk
 Moistens air
(becomes ligamentum arteriosum at birth)
 Traps incoming foreign particles
Age-related problems associated with the cardiovascular  Enzymes in the mucus destroy bacteria chemically
system include:
 Weakening of venous valves
 Varicose veins Conchae are projections from the lateral walls
 Progressive arteriosclerosis
 Increase surface area
 Increase air turbulence within the nasal cavity  Palatine tonsils (2) are located in the oropharynx at the
end of the soft palate
 Increased trapping of inhaled particles
 Lingual tonsils (2) are found at the base of the tongue
 The palate separates the nasal cavity from the

oral cavity
The Larynx
 Hard palate is anterior and supported by bone
 Commonly called the voice box
 Soft palate is posterior and unsupported
 Located inferior to the pharynx

 Made of:
Paranasal sinuses
 eight rigid hyaline cartilages
 Cavities within the frontal, sphenoid, ethmoid, and
maxillary bones surrounding the nasal cavity  Thyroid cartilage (Adam’s apple) is the largestq
 Sinuses:
 spoon-shaped flap of elastic cartilage - epiglottis
 Lighten the skull
 Functions
 Act as resonance chambers for speech
 Routes air and food into proper channels
 Produce mucus
 Plays a role in speech

The Pharynx Epiglottis

 Commonly called the throat  Spoon-shaped flap of elastic cartilage

 Muscular passageway from nasal cavity to larynx  Protects the superior opening of the larynx

 Continuous with the posterior nasal aperture  Routes food to the posteriorly situated esophagus and
routes air toward the trachea
 Serves as common passageway for food and air
 During swallowing, the epiglottis rises and forms a lid
 Three regions of the pharynx over the opening of the larynx

1. Nasopharynx—superior region behind nasal cavity Vocal folds (true vocal cords)

2. Oropharynx—middle region behind mouth  Vibrate with expelled air which allow us to speak

3. Laryngopharynx—inferior region attached to larynx  The glottis includes the vocal cords and the opening
between the vocal cords

Oropharynx and laryngopharynx serve as

The Trachea
common passageway for air and food
 Commonly called the windpipe
 Epiglottis routes food into the posterior tube, the
esophagus  4-inch-long tube that connects to the larynx
 Pharyngotympanic tubes open into the nasopharynx
 Walls are reinforced with C-shaped rings of hyaline
 Drain the middle ear
cartilage, which keep the trachea patent (open)
 Lined with ciliated mucosa
Tonsils are clusters of lymphatic tissue that play a
 Cilia beat continuously in the opposite direction of
role in protecting the body from infection incoming air
 Expel mucus loaded with dust and other debris away
 Pharyngeal tonsil (adenoid), a single tonsil, is located in from lungs
the nasopharynx
  Terminal bronchioles lead into respiratory zone
The Main Bronchi structures and terminate in alveoli

 Formed by division of the trachea  Respiratory zone includes the:

 Each bronchus enters the lung at the hilum (medial  Respiratory bronchioles
depression)
 Alveolar ducts
 Right bronchus is wider, shorter, and straighter than
 Alveolar sacs
left
 Alveoli (air sacs)—the only site of gas exchange
 Bronchi subdivide into smaller and smaller branches
 Conducting zone structures include all other
passageways
The Lungs

 Occupy the entire thoracic cavity except for the central Alveoli
mediastinum
 Simple squamous epithelial cells largely compose the
 Apex of each lung is near the clavicle (superior portion) walls
 Base rests on the diaphragm
 Alveolar pores connect neighboring air sacs
 Each lung is divided into lobes by fissures
 Pulmonary capillaries cover external surfaces of alveoli
 Left lung—two lobes

 Right lung—three lobes

Respiratory membrane (air-blood barrier)

 On one side of the membrane is air, and on the other

Serosa covers the outer surface of the lungs
side is blood flowing past
 Pulmonary (visceral) pleura covers the lung surface
 Formed by alveolar and capillary walls
 Parietal pleura lines the walls of the thoracic cavity  Gas crosses the respiratory membrane by diffusion
 Oxygen enters the blood
 Pleural fluid fills the area between layers
 Carbon dioxide enters the alveoli
 Allows the lungs to glide over the thorax

 Decreases friction during breathing Alveolar macrophages (―dust cells‖)

 Pleural space (between the layers) is more of a  Add protection by picking up bacteria, carbon particles,
potential space and other debris

 Surfactant (a lipid molecule)

The bronchial tree
 Coats gas-exposed alveolar surfaces
 Main bronchi subdivide into smaller and smaller
 Secreted by cuboidal surfactant-secreting cells
branches

 Bronchial (respiratory) tree is the network of branching

Respiratory Physiology
passageways
 All but the smallest passageways have reinforcing  Functions of the respiratory system
cartilage in the walls
 Supply the body with oxygen
 Conduits to and from the respiratory zone
 Bronchioles (smallest conducting passageways)  Dispose of carbon dioxide

 Respiration includes four distinct events

Respiratory Zone Structures and the
 Pulmonary ventilation
Respiratory Membrane
 External respiration
 Respiratory gas transport  Forced expiration can occur mostly by contraction of
internal intercostal muscles to depress the rib cage
 Internal respiration

Intrapleural pressure
Four events of respiration
 The pressure within the pleural space is always
1. Pulmonary ventilation—moving air into and out of the
negative
lungs (commonly called breathing)
 Major factor preventing lung collapse
2. External respiration—gas exchange between  If intrapleural pressure equals atmospheric pressure,
pulmonary blood and alveoli the lungs recoil and collapse
 Oxygen is loaded into the blood
 Carbon dioxide is unloaded from the blood
Respiratory Volumes and Capacities
3. Respiratory gas transport—transport of oxygen and
carbon dioxide via the bloodstream  Factors affecting respiratory capacity
4. Internal respiration—gas exchange between blood and  Size
tissue cells in systemic capillaries  Sex
 Age
 Physical condition
Mechanics of Breathing

 Pulmonary ventilation
 Tidal volume (TV)
 Mechanical process that depends on volume changes in  Normal quiet breathing
the thoracic cavity
 500 ml of air is moved in/out of lungs with each breath
 RULE:

 Volume changes lead to pressure changes, which lead

Inspiratory reserve volume (IRV)
to the flow of gases to equalize pressure
 Amount of air that can be taken in forcibly over the
tidal volume
Two phases of pulmonary ventilation
 Usually around 3,100 ml
 Inspiration = inhalation
 Expiratory reserve volume (ERV)
 Flow of air into lungs  Amount of air that can be forcibly exhaled after a tidal
 Expiration = exhalation expiration
 Air leaving lungs  Approximately 1,200 ml

Inspiration (inhalation) Residual volume

 Diaphragm and external intercostal muscles contract  Air remaining in lung after expiration
 Cannot be voluntarily exhaled
 Intrapulmonary volume increases  Allows gas exchange to go on continuously, even
 Gas pressure decreases between breaths, and helps keep alveoli open (inflated)
 Air flows into the lungs until intrapulmonary pressure  About 1,200 ml
equals atmospheric pressure

Expiration (exhalation)
Vital capacity
 Largely a passive process that depends on natural lung
elasticity  The total amount of exchangeable air
 Intrapulmonary volume decreases  Vital capacity = TV + IRV + ERV
 Gas pressure increases  4,800 ml in men; 3,100 ml in women
 Gases passively flow out to equalize the pressure
 Dead space volume
 Air that remains in conducting zone and never reaches  Oxygen is loaded into the blood
alveoli
 Oxygen diffuses from the oxygen-rich air of the alveoli
 About 150 ml
to the oxygen-poor blood of the pulmonary capillaries
 Carbon dioxide is unloaded out of the blood
Functional volume  Carbon dioxide diffuses from the blood of the
pulmonary capillaries to the alveoli
 Air that actually reaches the respiratory zone

 Usually about 350 ml

Internal Respiration
 Respiratory capacities are measured with a spirometer
 Exchange of gases between blood and tissue cells
 An opposite reaction from what occurs in the lungs
Nonrespiratory Air Movements  Carbon dioxide diffuses out of tissue cells to blood
(called loading)
 Can be caused by reflexes or voluntary actions
 Oxygen diffuses from blood into tissue (called
 Examples unloading)
 Cough and sneeze—clears lungs of debris

 Crying—emotionally induced mechanism Gas Transport in the Blood

 Laughing—similar to crying  Oxygen transport in the blood
 Hiccup—sudden inspirations  Most oxygen travels attached to hemoglobin and forms
 Yawn—very deep inspiration oxyhemoglobin (HbO2)
 A small dissolved amount is carried in the plasma
Carbon dioxide transport in the blood
Respiratory Sounds
 Most carbon dioxide is transported in the plasma as
 Sounds are monitored with a stethoscope bicarbonate ion (HCO3–)
 Two recognizable sounds can be heard with a  A small amount is carried inside red blood cells on
stethoscope: hemoglobin, but at different binding sites from those of
oxygen

1. Bronchial sounds—produced by air rushing through

large passageways such as the trachea and bronchi  For carbon dioxide to diffuse out of blood into the
2. Vesicular breathing sounds—soft sounds of air filling alveoli, it must be released from its bicarbonate form:
alveoli  Bicarbonate ions enter RBC
 Combine with hydrogen ions
 Form carbonic acid (H2CO3)
External Respiration, Gas Transport, and Internal  Carbonic acid splits to form water + CO2
Respiration  Carbon dioxide diffuses from blood into alveoli

 Gas exchanges occur as a result of diffusion Control of Respiration

 External respiration is an exchange of gases occurring
between the alveoli and pulmonary blood (pulmonary  Neural regulation: setting the basic rhythm
gas exchange)  Activity of respiratory muscles is transmitted to and
 Internal respiration is an exchange of gases occurring from the brain by phrenic and intercostal nerves
between the blood and tissue cells (systemic capillary  Neural centers that control rate and depth are located
gas exchange) in the medulla and pons
 Movement of the gas is toward the area of lower
concentration  Medulla—sets basic rhythm of breathing and contains a
pacemaker (self-exciting inspiratory center) called the
ventral respiratory group (VRG)
External Respiration
 Pons—smooth out respiratory rate Hypoventilation

 Results when blood becomes alkaline (alkalosis)

Normal respiratory rate (eupnea)
 Extremely slow or shallow breathing
 12 to 15 respirations per minut  Allows CO2 to accumulate in the blood

 Hyperpnea

 Increased respiratory rate, often due to extra oxygen Respiratory Disorders

needs  Chronic obstructive pulmonary disease (COPD)

 Exemplified by chronic bronchitis and emphysema

Non-neural factors influencing respiratory rate and depth  Shared features of these diseases
 Physical factors
1. Patients almost always have a history of smoking
 Increased body temperature
2. Labored breathing (dyspnea) becomes progressively
 Exercise
worse
 Talking 3. Coughing and frequent pulmonary infections are
common
 Coughing
4. Most COPD patients are hypoxic, retain carbon dioxide
 Volition (conscious control) and have respiratory acidosis, and ultimately develop
respiratory failure
 Emotional factors such as fear, anger, and excitement

Chronic bronchitis
Chemical factors: CO2 levels
 The body’s need to rid itself of CO2  Mucosa of the lower respiratory passages becomes
severely inflamed
is the most important stimulus for breathing  Excessive mucus production impairs ventilation and gas
 Increased levels of carbon dioxide (and thus, a exchange
decreased or acidic pH) in the blood increase the rate  Patients become cyanotic and are sometimes called
and depth of breathing ―blue bloaters‖ as a result of chronic hypoxia and
 Changes in carbon dioxide act directly on the medulla carbon dioxide retention
oblongata

Emphysema
Chemical factors: oxygen levels
 Alveoli walls are destroyed; remaining alveoli enlarge
 Changes in oxygen concentration in the blood are
detected by chemoreceptors in the aorta and common  Chronic inflammation promotes lung fibrosis, and lungs
carotid artery lose elasticity
 Patients use a large amount of energy to exhale; some
 Information is sent to the medulla air remains in the lungs
 Oxygen is the stimulus for those whose systems have  Sufferers are often called ―pink puffers‖ because
become accustomed to high levels of carbon dioxide as a oxygen exchange is efficient
result of disease  Overinflation of the lungs leads to a permanently
expanded barrel chest
 Cyanosis appears late in the disease
 Hyperventilation

 Rising levels of CO2in the blood (acidosis) result in Lung cancer

faster, deeper breathing
 Leading cause of cancer death for men and women
 Exhale more CO2 to elevate blood pH
 May result in apnea and dizziness and lead to alkalosis  Nearly 90 percent of cases result from smoking

 Aggressive cancer that metastasizes rapidly

 Three common types Chaper 14: The Digestive System

1. Adenocarcinoma The Digestive System Functions

2. Squamous cell carcinoma  Ingestion—taking in food

3. Small cell carcinoma  Digestion—breaking food into nutrient molecules

 Absorption—movement of nutrients into the

bloodstream
Developmental Aspects of the Respiratory System
 Defecation—excretes to rid the body of indigestible
 Lungs do not fully inflate until 2 weeks after birth
waste
 This change from nonfunctional to functional
respiration depends on surfactant
Anatomy of the Digestive System
 Surfactant lowers surface tension so the alveoli do not
 Two main groups of organs
collapse
 Alimentary canal (gastrointestinal, or GI, tract)—
 Surfactant is formed late in pregnancy, around 28 to 30
continuous, coiled, hollow tube
weeks
 These organs ingest, digest, absorb, defecate

Respiratory rate changes throughout life  Accessory digestive organs

 Newborns: 40 to 80 respirations per minute  Include teeth, tongue, and several large digestive
organs
 Infants: 30 respirations per minute
 Assist digestion in various ways
 Age 5: 25 respirations per minute

 Adults: 12 to 18 respirations per minute Organs of the Alimentary Canal

 Rate often increases again in old age  The alimentary canal is a continuous, coiled, hollow
tube that runs through the ventral cavity from stomach
to anus
Asthma  Mouth
 Chronically inflamed, hypersensitive bronchiole  Pharynx
passages
 Respond to irritants with dyspnea, coughing, and  Esophagus
wheezing
 Stomach

 Small intestine
Youth and middle age  Large intestine
 Anus
 Most respiratory system problems are a result of
external factors, such as infections and substances that Mouth
physically block respiratory passageways
 Aging effects
 Anatomy of the mouth
 Elasticity of lungs decreases
 Vital capacity decreases  Mouth (oral cavity)—mucous membrane–lined cavity
 Blood oxygen levels decrease
 Lips (labia)—protect the anterior opening
 Stimulating effects of carbon dioxide decrease
 Cheeks—form the lateral walls
 Elderly are often hypoxic and exhibit sleep apnea
 Hard palate—forms the anterior roof
 More risks of respiratory tract infection
 Soft palate—forms the posterior roof
 Uvula—fleshy projection of the soft palate  Conducts food by peristalsis (slow rhythmic squeezing)
to the stomach
 Passageway for food only (respiratory system branches
Mouth
off after the pharynx)
 Vestibule—space between lips externally and teeth and
gums internally
Layers of Tissue in the Alimentary Canal Organs
 Oral cavity proper—area contained by the teeth
 Summary of the four layers from innermost to
 Tongue—attached at hyoid bone and styloid processes
outermost, from esophagus to the large intestine
of the skull, and by the lingual frenulum to the floor of
the mouth 1. Mucosa

2. Submucosa
Tonsils
3. Muscularis externa
 Palatine—located at posterior end of oral cavity
4. Serosa
 Lingual—located at the base of the tongue

1. Mucosa
Functions of the mouth
 Innermost, moist membrane consisting of:
 Mastication (chewing) of food
 Surface epithelium that is mostly simple columnar
 Tongue mixes masticated food with saliva epithelium (except for esophagus—stratified squamous
epithelium)
 Tongue initiates swallowing
 Small amount of connective tissue (lamina propria)
 Taste buds on the tongue allow for taste
 Scanty smooth muscle layer

Pharynx  Lines the cavity (known as the lumen)

 Serves as a passageway for foods, fluids, and air
 Food passes from the mouth posteriorly into the:
 Oropharynx—posterior to oral cavity 2. Submucosa
 Laryngopharynx—below the oropharynx and
continuous with the esophagus  Just beneath the mucosa

 Soft connective tissue with blood vessels, nerve

Food is propelled to the esophagus by two skeletal endings, mucosa-associated lymphoid tissue, and
muscle layers in the pharynx lymphatic vessels

 Longitudinal outer layer

 Circular inner layer 3. Muscularis externa—smooth muscle

 Inner circular layer
 Alternating contractions of the muscle layers
(peristalsis) propel the food  Outer longitudinal layer

Esophagus 4. Serosa—outermost layer of the wall; contains fluid-

producing cells
 Anatomy
 Visceral peritoneum—innermost layer that is
 About 10 inches long continuous with the outermost layer
 Runs from pharynx to stomach through the diaphragm  Parietal peritoneum—outermost layer that lines the
abdominopelvic cavity by way of the mesentery
 Physiology
Alimentary Canal Nerve Plexuses  Simple columnar epithelium composed almost entirely
of mucous cells
 Alimentary canal wall contains two intrinsic nerve
plexuses that are part of the autonomic nervous system  Mucous cells produce bicarbonate-rich alkaline mucus

 Submucosal nerve plexus  Dotted by gastric pits leading to gastric glands that
secrete gastric juice, including:
 Myenteric nerve plexus
 Intrinsic factor, which is needed for vitamin B12
 Regulate mobility and secretory activity of the GI tract
absorption in the small intestine
organs

Stomach Chief cells—produce protein-digesting enzymes

(pepsinogens)
 C-shaped organ located on the left side of the
 Parietal cells—produce hydrochloric acid that activates
abdominal cavity
enzymes
 Food enters at the cardioesophageal sphincter from the
 Mucous neck cells—produce thin acidic mucus
esophagus
(different from the mucus produced by mucous cells of
 Food empties into the small intestine at the pyloric the mucosa)
sphincter (valve)
 Enteroendocrine cells—produce local hormones such
as gastrin

Regions

 Cardial (cardia)—near the heart and surrounds the Small Intestine

cardioesophageal sphincter
 The body’s major digestive organ
 Fundus—expanded portion lateral to the cardiac region
 Longest portion of the alimentary tube (2–4 m, or 7–13
 Body—midportion feet, in a living person)

 Greater curvature is the convex lateral surface  Site of nutrient absorption into the blood

 Lesser curvature is the concave medial surface  Muscular tube extending from the pyloric sphincter to
the ileocecal valve
 Pylorus—funnel-shaped terminal end  Suspended from the posterior abdominal wall by the
Stomach can stretch and hold 4 L (1 gallon) of food when mesentery
full

 Rugae—internal folds of the mucosa present when the Functions

stomach is empty
 Temporary storage tank for food

 Site of food breakdown

 Lesser omentum
 Chemical breakdown of protein begins
 Double layer of the peritoneum
 Delivers chyme (processed food) to the small intestine
 Extends from liver to the lesser curvature of stomach
Subdivisions
 Greater omentum
 Duodenum
 Another extension of the peritoneum
 Jejunum
 Covers the abdominal organs
 Ileum
 Fat insulates, cushions, and protects abdominal organs

Chemical digestion begins in the small intestine

Structure of the stomach mucosa
 Enzymes produced by intestinal cells and pancreas are  Cecum—saclike first part of the large intestine
carried to the duodenum by pancreatic ducts
 Appendix
 Bile, formed by the liver, enters the duodenum via the
 Hangs from the cecum
bile duct
 Accumulation of lymphoid tissue that sometimes
becomes inflamed (appendicitis)
 Hepatopancreatic ampulla is the location where the
main pancreatic duct and bile ducts join  Colon
 Structural modifications  Ascending—travels up right side of abdomen and
makes a turn at the right colic (hepatic) flexure
 Increase surface area for food absorption

 Decrease in number toward the end of the small

 Transverse—travels across the abdominal cavity and
intestine
turns at the left colic (splenic) flexure

 Descending—travels down the left side

1. Villi—fingerlike projections formed by the mucosa
 Sigmoid—S-shaped region; enters the pelvis
 House a capillary bed and lacteal
 Sigmoid colon, rectum, and anal canal are located in
2. Microvilli—tiny projections of the plasma membrane
the pelvis
(brush border enzymes)
 Anal canal ends at the anus
3. Circular folds (plicae circulares)—deep folds of mucosa
and submucosa  Anus—opening of the large intestine

 External anal sphincter—formed by skeletal muscle and

 Peyer’s patches is voluntary
 Collections of lymphatic tissue  Internal anal sphincter—formed by smooth muscle and
is involuntary
 Located in submucosa

 Increase in number toward the end of the small

intestine  These sphincters are normally closed except during
defecation
 More are needed there because remaining food
residue contains much bacteria  The large intestine delivers indigestible food residues to
the body’s exterior
Large Intestine  Goblet cells produce alkaline mucus to lubricate the
passage of feces
 Larger in diameter, but shorter in length at 1.5 m, than
the small intestine  Muscularis externa layer is reduced to three bands of
muscle, called teniae coli
 Extends from the ileocecal valve to the anus
 These bands of muscle cause the wall to pucker into
haustra (pocketlike sacs)
 Subdivisions (detailed next)

 Cecum
Accessory Digestive Organs
 Appendix
 Teeth
 Colon
 Salivary glands
 Rectum
 Pancreas
 Anal canal
 Liver
 Gallbladder
  Three pairs of salivary glands empty secretions into the
mouth
Teeth
1. Parotid glands
 Teeth masticate (chew) food into smaller fragments
 Humans have two sets of teeth during a lifetime  Found anterior to the ears
1. Deciduous (baby or milk) teeth
 Mumps affect these salivary glands
 A baby has 20 teeth by age 2
2. Submandibular glands
 First teeth to appear are the lower central incisors
3. Sublingual glands
2. Permanent teeth
 Both submandibular and sublingual glands empty saliva
 Replace deciduous teeth between ages 6 and 12 into the floor of the mouth through small ducts

 A full set is 32 teeth (with the wisdom teeth)

 Saliva

Teeth are classified according to shape and function  Mixture of mucus and serous fluids
 Incisors—cutting
 Helps to moisten and bind food together into a mass
 Canines (eyeteeth)—tearing or piercing
called a bolus
 Premolars (bicuspids)—grinding
 Molars—grinding  Contains:

 Salivary amylase—begins starch digestion

Two major regions of a tooth  Lysozymes and antibodies—inhibit bacteria
1. Crown  Dissolves chemicals so they can be tasted
2. Root
Pancreas
1. Crown—exposed part of tooth above the gingiva (gum)  Soft, pink triangular gland

 Enamel—covers the crown  Found posterior to the parietal peritoneum

 Dentin—found deep to the enamel and forms the bulk  Mostly retroperitoneal
of the tooth, surrounds the pulp cavity
 Extends across the abdomen from spleen to duodenum
 Pulp cavity—contains connective tissue, blood vessels,
and nerve fibers (pulp)  Produces a wide spectrum of digestive enzymes that
break down all categories of food
 Root canal—where the pulp cavity extends into the
root  Secretes enzymes into the duodenum

2. Root  Alkaline fluid introduced with enzymes neutralizes

acidic chyme coming from stomach
 Cement—covers outer surface and attaches the tooth
to the periodontal membrane (ligament)

 Periodontal membrane holds tooth in place in the bony  Hormones produced by the pancreas
jaw  Insulin
Note: The neck is a connector between the crown
 Glucagon
and root

 Region in contact with the gum Liver

Salivary Glands  Largest gland in the body

 Located on the right side of the body under the  Examples
diaphragm
 Mixing of food in the mouth by the tongue
 Consists of four lobes suspended from the diaphragm
 Churning of food in the stomach
and abdominal wall by the falciformligament
 Segmentation in the small intestine

 Mechanical digestion prepares food for further

 Digestive role is to produce bile
degradation by enzymes
 Bile leaves the liver through the common hepatic duct
and enters duodenum through the bile duct
4. Food breakdown: digestion
 Bile is yellow-green, watery solution containing:
 Digestion occurs when enzymes chemically break down
 Bile salts and bile pigments (mostly bilirubin from the
large molecules into their building blocks
breakdown of hemoglobin)
 Each major food group uses different enzymes
 Cholesterol, phospholipids, and electrolytes  Carbohydrates are broken down to
monosaccharides(simple sugars)
 Bile emulsifies (breaks down) fats
 Proteins are broken down to amino acids
Gallbladder
 Fats are broken down to fatty acids and glycerol
 Green sac found in a shallow fossa in the inferior
surface of the liver
5. Absorption
 When no digestion is occurring, bile backs up the cystic
duct for storage in the gallbladder  End products of digestion are absorbed in the blood or
lymph
 While in the gallbladder, bile is concentrated by the
removal of water  Food must enter mucosal cells and then move into
 When fatty food enters the duodenum, the gallbladder blood or lymph capillaries
spurts out stored bile 6. Defecation

 Elimination of indigestible substances from the GI tract

Functions of the Digestive System in the form of feces
 Overview of gastrointestinal processes and controls
Activities Occurring in the Mouth, Pharynx, and
 Digestion
Esophagus
 Absorption
 Food ingestion and breakdown

 Food is placed into the mouth

Overview of Gastrointestinal Processes and Controls
 Physically broken down by chewing
 Essential processes of the GI tract
 Mixed with saliva, which is released in response to
1. Ingestion—placing of food into the mouth
mechanical pressure and psychic stimuli
2. Propulsion—movement of foods from one region of
the digestive system to another
 Salivary amylase begins starch digestion
 Peristalsis—alternating waves of contraction and
 Essentially, no food absorption occurs in the mouth
relaxation that squeeze food along the GI tract
Segmentation—movement of materials back and forth Food propulsion—swallowing and peristalsis
to foster mixing in the small intestine  Pharynx and esophagus have no digestive function
3. Food breakdown: mechanical breakdown  Serve as passageways to the stomach
 Pharynx functions in swallowing (deglutition)  Food propulsion

1. Peristalsis: waves of peristalsis occur from the fundus

 Two phases of swallowing to the pylorus, forcing food past the pyloric sphincter

1. Buccal phase 2. Grinding: the pylorus meters out chyme into the small
intestine (3 ml at a time)
 Voluntary (Occurs in the mouth)
3. Retropulsion: peristaltic waves close the pyloric
 Food is formed into a bolus
sphincter, forcing contents back into the stomach; the
 The bolus is forced into the pharynx by the tongue stomach empties in 4–6 hours

2. Pharyngeal-esophageal phase Activities of the Small Intestine

 Involuntary transport of the bolus by peristalsis  Chyme breakdown and absorption

 Nasal and respiratory passageways are blocked  Intestinal enzymes from the brush border function to:

 Peristalsis moves the bolus toward the stomach  Break double sugars into simple sugars

 The cardioesophageal sphincter is opened when food  Complete some protein digestion
presses against it
 Intestinal enzymes and pancreatic enzymes help to
complete digestion of all food groups
Activities in the Stomach
 Pancreatic enzymes play the major role in the digestion
 Food breakdown of fats, proteins, and carbohydrates

 Gastric juice is regulated by neural and hormonal  Alkaline content neutralizes acidic chyme and provides
factors the proper environment for the pancreatic enzymes to
operate
 Presence of food or rising pH causes the release of the
hormone gastrin
 Release of pancreatic juice from the pancreas into the
 Gastrin causes stomach glands to produce: duodenum is stimulated by:
 Protein-digesting enzymes  Vagus nerves
- Local hormones that travel via the blood to influence
 Mucus the release of pancreatic juice (and bile)
 Hydrochloric acid  Secretin
 Hydrochloric acid makes the stomach contents very  Cholecystokinin (CCK)
acidic
- Hormones (secretin and CCK) also target the liver and
gallbladder to release bile
 Acidic pH

 Activates pepsinogen to pepsin for protein digestion  Bile

 Provides a hostile environment for microorganisms  Acts as a fat emulsifier
 Protein-digestion enzymes  Needed for fat absorption and absorption of fat-soluble
 Pepsin—an active protein-digesting enzyme vitamins (K, D, E, and A)

 Rennin—works on digesting milk protein in infants; not  Water is absorbed along the length of the small
produced in adults intestine
 End products of digestion
 Alcohol and aspirin are virtually the only items  Most substances are absorbed by active transport
absorbed in the stomach through cell membranes
 Lipids are absorbed by diffusion
 Substances are transported to the liver by the hepatic  Foods are oxidized and transformed into adenosine
portal vein or lymph triphosphate (ATP)
 ATP is chemical energy that drives cellular activities
 Energy value of food is measured in kilocalories (kcal)
 Chyme propulsion
or Calories (C)
 Peristalsis is the major means of moving food

 Segmental movements
Nutrition
 Mix chyme with digestive juices
 Nutrient—substance used by the body for growth,
 Aid in propelling food maintenance, and repair

 Major nutrients: Carbohydrates, Lipids, Proteins, Water

Activities of the Large Intestine
 Minor nutrients: Vitamins, Minerals
 Nutrient breakdown and absorption
A diet consisting of foods from the five food groups
 No digestive enzymes are produced normally guarantees adequate amounts of all the needed
nutrients
 Resident bacteria digest remaining nutrients

 Produce some vitamin K and some B vitamins

Dietary Recommendations
 Release gases
 Healthy Eating Pyramid
 Water, vitamins, ions, and remaining water are  Issued in 1992
absorbed
 Remaining materials are eliminated via feces  Six major food groups arranged horizontally

 MyPlate
 Feces contains:
 Issued in 2011 by the USDA
 Undigested food residues
 Five food groups are arranged by a round plate
 Mucus

 Bacteria
Dietary Sources of the Major Nutrients
 Water
 Carbohydrates
 Propulsion of food residue and defecation
 Dietary carbohydrates are sugars and starches
 Sluggish peristalsis begins when food residue arrives
 Most are derived from plants such as fruits and
 Haustral contractions are the movements occurring vegetables
most frequently in the large intestine  Exceptions: lactose from milk and small amounts of
glycogens from meats

 Mass movements are slow, powerful movements that

occur three to four times per day  Lipids

 Presence of feces in the rectum causes a defecation  Saturated fats from animal products (meats)
reflex
 Unsaturated fats from nuts, seeds, and vegetable oils
 Internal anal sphincter is relaxed
 Cholesterol from egg yolk, meats, and milk products
 Defecation occurs with relaxation of the voluntary (dairy products)
(external) anal sphincter

 Proteins
Part II: Nutrition and Metabolism
 Complete proteins—contain all essential amino acids
 Most foods are used as metabolic fuel
 Most are from animal products (eggs, milk, meat,  Energizes a glucose molecule so it can be split into two
poultry, and fish) pyruvic acid molecules and yield ATP

 Essential amino acids: those that the body cannot make

and must be obtained through diet 2. Citric acid cycle (Krebs cycle)

 Legumes and beans also have proteins, but the proteins  Occurs in the mitochondrion
are incomplete
 Produces virtually all the carbon dioxide and water
resulting from cellular respiration

 Vitamins  Yields a small amount of ATP

 Most vitamins function as coenzymes

3. Electron transport chain
 Found mainly in fruits and vegetables
 Hydrogen atoms removed during glycolysis and the
 Minerals
citric acid cycle are delivered to protein carriers
 Mainly important for enzyme activity
 Hydrogen atoms are split into hydrogen ions and
 Foods richest in minerals: vegetables, legumes, milk, electrons in the mitochondria
and some meats
 Electrons give off energy in a series of steps to enable
the production of ATP

Metabolism
 Hyperglycemia—excessively high levels of glucose in
 Metabolism is all of the chemical reactions necessary to the blood
maintain life
 Excess glucose is stored in body cells as glycogen or
 Catabolism—substances are broken down to simpler converted to fat
substances; energy is released and captured to make
adenosine triphosphate (ATP)  Hypoglycemia—low levels of glucose in the blood

 Anabolism—larger molecules are built from smaller  Glycogenolysis, gluconeogenesis, and fat breakdown
ones occur to restore normal blood glucose levels

Carbohydrate Metabolism Fat Metabolism

 Carbohydrates are the body’s preferred source to  Fats :

produce cellular energy (ATP)
 Insulate the body
 Glucose (blood sugar)
 Protect organs
 Major breakdown product of carbohydrate digestion
 Build some cell structures (membranes and myelin
 Fuel used to make ATP sheaths)

Cellular respiration  Provide reserve energy

 As glucose is oxidized, carbon dioxide, water, and ATP  Excess dietary fat is stored in subcutaneous tissue and
are formed other fat depots

Events of three main metabolic pathways of cellular  When carbohydrates are in limited supply, more fats
respiration are oxidized to produce ATP

1. Glycolysis
 Excessive fat breakdown causes blood to become acidic
 Occurs in the cytosol (acidosis or ketoacidosis)

 Breath has a fruity odor

 Common with:  Some are oxidized to provide energy for liver cells

 ―No carbohydrate‖ diets  The rest are either stored or broken down into simpler
compounds and released into the blood
 Uncontrolled diabetes mellitus
 Blood proteins made by the liver are assembled from
 Starvation
amino acids

 Albumin is the most abundant protein in blood

Protein Metabolism
 Clotting proteins
 Proteins form the bulk of cell structure and most
 Liver cells detoxify ammonia
functional molecules
 Proteins are carefully conserved by body cells  Ammonia is combined with carbon dioxide to form
 Amino acids are actively taken up from blood by body urea, which is flushed from the body in urine
cells

 Amino acids are oxidized to form ATP mainly when

Cholesterol metabolism and transport
other fuel sources are not available
 Ammonia, released as amino acids are catabolized, is  Cholesterol is not used to make ATP
detoxified by liver cells that combine it with carbon
dioxide to form urea  Functions of cholesterol:

 Structural basis of steroid hormones and vitamin D

The Central Role of the Liver in Metabolism  Building block of plasma membranes
 Liver is the body’s key metabolic organ  Most cholesterol (85%) is produced in the liver; only
 Roles in digestion 15% is from the diet

 Manufactures bile

 Detoxifies drugs and alcohol Cholesterol and fatty acids cannot freely circulate in

 Degrades hormones the bloodstream

 Produces cholesterol, blood proteins (albumin and  They are transported by lipoproteins (lipid-protein
clotting proteins) complexes) known as LDLs and HDLs

 Plays a central role in metabolism Low-density lipoproteins (LDLs) transport cholesterol to

body cells
 Liver can regenerate if part of it is damaged or removed
 Rated ―bad lipoproteins‖ since they can lead to
atherosclerosis
To maintain homeostasis of blood glucose levels, the liver  High-density lipoproteins (HDLs) transport cholesterol
performs: from body cells to the liver
 Rated ―good lipoproteins‖ since cholesterol is destined
 Glycogenesis—―glycogen formation‖
for breakdown and elimination
 Glucose molecules are converted to glycogen and
stored in the liver
Body Energy Balance
 Glycogenolysis—―glycogen splitting‖
 Energy intake = Total energy output (heat + work +
 Glucose is released from the liver after conversion from
energy storage)
glycogen
 Energy intake is the energy liberated during food
 Gluconeogenesis—―formation of new sugar‖ oxidation
 Energy produced during glycolysis, citric acid cycle, and
 Glucose is produced from fats and proteins
the electron transport chain

Fats and fatty acids are picked up by the liver

 Energy output
 Energy we lose as heat (60%) activity
 TMR must equal calories consumed to maintain
 Energy stored as fat or glycogen
homeostasis and maintain a constant weight

Interference with the body’s energy balance leads to: Body temperature regulation

 Obesity  When foods are oxidized, more than 60% of energy

escapes as heat, warming the body
 Malnutrition (leading to body wasting)
 The body has a narrow range of homeostatic
temperature
Regulation of food intake  Must remain between 35.6ºC and 37.8ºC
 Body weight is usually relatively stable  (96ºF and 100ºF)
 Energy intake and output remain about equal

 Mechanisms that may regulate food intake Body temperature regulation

 Levels of nutrients in the blood  The body’s thermostat is in the hypothalamus
 Hormones  Hypothalamus initiates mechanisms to maintain body
 Body temperature temperature

 Psychological factor  Heat loss mechanisms involve radiation of heat from

skin and evaporation of sweat

 Heat-promoting mechanisms involve vasoconstriction

Metabolic rate and body heat production of skin blood vessels and shivering
 Nutrients yield different amounts of energy

 Energy value is measured in kilocalories (kcal) Fever—controlled hyperthermia

 Carbohydrates and proteins yield 4 kcal/gram  Results from infection, cancer, allergic reactions, CNS
 Fats yield 9 kcal/gram injuries

 Basic metabolic rate (BMR)—amount of heat produced  If the body thermostat is set too high, body proteins
by the body per unit of time at rest may be denatured, and permanent brain damage may
occur
 Average BMR is about 60 to 72 kcal/hour for an
average 70-kg (154-lb) adult
Part III: Developmental Aspects of the

Factors that influence BMR Digestive System and Metabolism

 Surface area—a small body usually has a higher BMR  The alimentary canal is a continuous, hollow tube
present by the fifth week of development
 Gender—males tend to have higher BMRs  Digestive glands bud from the mucosa of the
alimentary tube
 Age—children and adolescents have higher BMRs
 The developing fetus receives all nutrients through the
 The amount of thyroxine produced is the most placenta
important control factor
 In newborns, feeding must be frequent, peristalsis is
inefficient, and vomiting is common
 More thyroxine means a higher metabolic rate

Total metabolic rate (TMR)—total amount of kilocalories

Developmental Aspects of the Digestive System and
the body must consume to fuel ongoing activities
Metabolism
 TMR increases dramatically with an increase in muscle
 Newborn reflexes  Production of erythropoietin to stimulate red blood cell
 Rooting reflex helps the infant find the nipple production
 Sucking reflex helps the infant hold on to the nipple
 Conversion of vitamin D to its active form
and swallow
 Teething begins around age 6 months
Organs of the Urinary System

 Kidneys
 Problems of the digestive system
 Ureters
 Gastroenteritis—inflammation of the gastrointestinal
tract; can occur at any time  Urinary bladder
 Appendicitis—inflammation of the appendix; common  Urethra
in adolescents

 Metabolism decreases with old age Kidneys

 Middle-age digestive problems  Location and structure
 The kidneys are situated against the dorsal body wall
 Ulcers
in a retroperitoneal position (behind the parietal
 Gallbladder problems
peritoneum)

 The kidneys are situated at the level of the T12 to L3

Developmental Aspects of the Digestive
vertebrae
System and Metabolism  The right kidney is slightly lower than the left (because
of position of the liver)
 Later middle-age problems

 Obesity
Kidney structure
 Diabetes mellitus
 An adult kidney is about 12 cm (5 in) long and 6 cm (2.5
 Activity of the digestive tract in old age
in) wide
 Fewer digestive juices

 Peristalsis slows  Renal hilum

 Diverticulosis and gastrointestinal cancers are more  A medial indentation where several structures enter or
common
exit the kidney (ureters, renal blood vessels, and nerves)

 An adrenal gland sits atop each kidney

Chapter 15: The Urinary System

Three protective layers enclose the kidney

Functions of the Urinary System
 Fibrous capsule encloses each kidney
 Kidneys dispose of waste products in urine
 Perirenal fat capsule surrounds the kidney and cushions
 Nitrogenous wastes
against blows
 Toxins

 Drugs  Renal fascia is the most superficial layer that anchors

the kidney and adrenal gland to surrounding structures
 Excess ions
Three regions revealed in a longitudinal section
 Kidneys’ regulatory functions include:
1. Renal cortex—outer region
 Production of renin to maintain blood pressure
2. Renal medulla—deeper region  Foot processes cling to the glomerulus

 Filtration slits create a porous membrane—ideal for

 Renal (medullary) pyramids—triangular regions of filtration
tissue in the medulla
2. Glomerular (Bowman’s) capsule is a cup-shaped
 Renal columns—extensions of cortexlike material that structure that surrounds the glomerulus
separate the pyramids
 First part of the renal tubule
3. Renal pelvis—medial region that is a flat, funnelshaped
tube
Renal tubule
 Calyces form cup-shaped ―drains‖ that enclose the
 Extends from glomerular capsule and ends when it
renal pyramids
empties into the collecting duct
 Calyces collect urine and send it to the renal pelvis, on
to the ureter, and to the urinary bladder for storage
 From the glomerular (Bowman’s) capsule, the
subdivisions of the renal tubule are:
 Blood supply
1. Proximal convoluted tubule (PCT)
 One-quarter of the total blood supply of the body
2. Nephron loop (loop of Henle)
passes through the kidneys each minute
3. Distal convoluted tubule (DCT)
 Renal artery provides each kidney with arterial blood
supply

 Renal artery divides into segmental arteries → Cortical nephrons

interlobar arteries → arcuate arteries → cortical radiate
arteries  Located entirely in the cortex

 Include most nephrons

Venous blood flow  Juxtamedullary nephrons
 Cortical radiate veins → arcuate veins → interlobar  Found at the cortex-medulla junction
veins → renal vein
 Nephron loop dips deep into the medulla
 There are no segmental veins
 Collecting ducts collect urine from both types of
 Renal vein returns blood to the inferior vena cava nephrons, through the renal pyramids, to the calyces,
and then to the renal pelvis
Nephrons

 Structural and functional units of the kidneys Two capillary beds associated with each nephron

 Each kidney contains over a million nephrons 1. Glomerulus

 Each nephron consists of two main structures 2. Peritubular capillary bed

1. Renal corpuscle
Glomerulus
2. Renal tubule
 Fed and drained by arterioles

 Afferent arteriole—arises from a cortical radiate artery

Renal corpuscle consists of: and feeds the glomerulus
1. Glomerulus, a knot of capillaries made of podocytes  Efferent arteriole—receives blood that has passed
through the glomerulus
 Podocytes make up the inner (visceral) layer of the
glomerular capsule  Specialized for filtration
 High pressure forces fluid and solutes out of blood and  Most reabsorption occurs in the proximal convoluted
into the glomerular capsule tubule

Peritubular capillary beds Tubular secretion

 Arise from the efferent arteriole of the glomerulus  Reabsorption in reverse

 Low-pressure, porous capillaries
 Some materials move from the blood of the peritubular
 Adapted for absorption instead of filtration
capillaries into the renal tubules to be eliminated in
 Cling close to the renal tubule to receive solutes and
filtrate
water from tubule cells
 Drain into the interlobar veins  Hydrogen and potassium ions

Urine Formation and Characteristics  Creatinine

 Urine formation is the result of three processes  Secretion is important for:
1. Glomerular filtration  Getting rid of substances not already in the filtrate
2. Tubular reabsorption
3. Tubular secretion  Removing drugs and excess ions

 Maintaining acid-base balance of blood

1. Glomerular filtration  Materials left in the renal tubule move toward the
 The glomerulus is a filter ureter

 Filtration is a nonselective passive process

Nitrogenous wastes
 Water and solutes smaller than proteins are forced
through glomerular capillary walls  Nitrogenous waste products are poorly reabsorbed, if
at all

 Proteins and blood cells are normally too large to pass  Tend to remain in the filtrate and are excreted from the
through the filtration membrane body in the urine
 Once in the capsule, fluid is called filtrate  Urea—end product of protein breakdown
 Filtrate leaves via the renal tubule
 Filtrate will be formed as long as systemic blood  Uric acid—results from nucleic acid metabolism
pressure is normal  Creatinine—associated with creatine metabolism in
 If arterial blood pressure is too low, filtrate formation muscles
stops because glomerular pressure will be too low to
form filtrate In 24 hours, about 1.0 to 1.8 liters of urine are produced

Tubular reabsorption  Urine and filtrate are different

 The peritubular capillaries reabsorb useful substances  Filtrate contains everything that blood plasma does
from the renal tubule cells, such as: (except proteins)

 Water  Urine is what remains after the filtrate has lost most of
its water, nutrients, and necessary ions through
 Glucose reabsorption
 Amino acids  Urine contains nitrogenous wastes and substances that
 Ions are not needed

 Some reabsorption is passive; most is active (ATP)

Urine characteristics

 Clear and pale to deep yellow in color

 Yellow color is normal and due to the pigment  Trigone—triangular region of the urinary bladder base
urochrome (from the destruction of hemoglobin) and based on three openings
solutes
 Two openings from the ureters (ureteral orifices)

 One opening to the urethra (internal urethral orifice)

 Dilute urine is a pale, straw color
 In males, the prostate surrounds the neck of the urinary
 Sterile at the time of formation
bladder
 Slightly aromatic, but smells like ammonia with time

 Slightly acidic (pH of 6) Wall of the urinary bladder

 Specific gravity of 1.001 to 1.035  Three layers of smooth muscle collectively called the
detrusor muscle

Solutes normally found in urine  Mucosa made of transitional epithelium

 Sodium and potassium ions  Walls are thick and folded in an empty urinary bladder

 Urea, uric acid, creatinine  Urinary bladder can expand significantly without
increasing internal pressure
 Ammonia

 Bicarbonate ions
Capacity of the urinary bladder

 A moderately full bladder is about 5 inches long and

Solutes NOT normally found in urine
holds about 500 ml of urine
 Glucose
 Capable of holding twice that amount of urine
 Blood proteins

 Red blood cells Urethra

 Hemoglobin  Thin-walled tube that carries urine from the urinary

bladder to the outside of the body by peristalsis
 WBCs (pus)
 Function
 Bile
 Females—carries only urine

Ureters  Males—carries urine and sperm

 Slender tubes 25–30 cm (10–12 inches) attaching the

kidney to the urinary bladder
Release of urine is controlled by two sphincters
 Continuous with the renal pelvis
1. Internal urethral sphincter
 Enter the posterior aspect of the urinary bladder
 Involuntary and made of smooth muscle
 Run behind the peritoneum
2. External urethral sphincter

 Voluntary and made of skeletal muscle

 Peristalsis aids gravity in urine transport

Urinary Bladder
Length
 Smooth, collapsible, muscular sac situated posterior to
the pubic symphysis  In females: 3 to 4 cm (1.5 inches long)

 Stores urine temporarily  In males: 20 cm (8 inches long)

 Location
 Females—anterior to the vaginal opening  Young adult males = 60%

 Males—travels through the prostate and penis  Babies = 75%

 Prostatic urethra  The elderly = 45%

 Membranous urethra  Water is necessary for many body functions, and levels
must be maintained
 Spongy urethra

Water occupies three main fluid compartments

Micturition
1. Intracellular fluid (ICF)
 Voiding, or emptying of the urinary bladder
 Fluid inside cells
 Two sphincters control the release of urine, the internal
urethral sphincter and external urethral sphincter  Accounts for two-thirds of body fluid

2. Extracellular fluid (ECF)

 Bladder collects urine to 200 ml
 Fluids outside cells; includes blood plasma, interstitial
 Stretch receptors transmit impulses to the sacral region fluid (IF), lymph, and transcellular fluid
of the spinal cord
3. Plasma (blood) is ECF, but accounts for 3L of total body
 Impulses travel back to the bladder via the pelvic water.
splanchnic nerves to cause bladder contractions

 Links external and internal environments

When contractions become stronger, urine is forced past The link between water and electrolytes
the involuntary internal sphincter into the upper urethra
 Electrolytes are charged particles (ions) that conduct
 Urge to void is felt electrical current in an aqueous solution

 The external sphincter is voluntarily controlled, so  Sodium, potassium, and calcium ions are electrolytes
micturition can usually be delayed

Regulation of water intake and output

Fluid, Electrolyte, and Acid-Base Balance  Water intake must equal water output if the body is to
remain properly hydrated
 Blood composition depends on three factors
 Sources for water intake
1. Diet
 Ingested foods and fluids
2. Cellular metabolism
 Water produced from metabolic processes (10%)
3. Urine output
 Thirst mechanism is the driving force for water intake

Kidneys have four roles in maintaining blood composition

Thirst mechanism
1. Excreting nitrogen-containing wastes (previously
discussed)  Osmoreceptors are sensitive cells in the hypothalamus
2. Maintaining water balance of the blood that become more active in reaction to small changes in
3. Maintaining electrolyte balance of the blood plasma solute concentration
4. Ensuring proper blood pH
 When activated, the thirst center in the hypothalamus
is notified
Maintaining Water Balance of the Blood  A dry mouth due to decreased saliva also promotes the
thirst mechanism
 Normal amount of water in the human body
 Both reinforce the drive to drink
 Young adult females = 50%
  Physiological acidosis—pH between 7.0 and 7.35

Sources of water output

 Lungs (insensible since we cannot sense the water Kidneys play greatest role in maintaining acidbase
leaving) balance

 Perspiration  Other acid-base controlling systems

 Feces  Blood buffers

 Urine
 Respiration

Hormones are primarily responsible for reabsorption of

water and electrolytes by the kidneys Blood buffers
 Antidiuretic hormone (ADH) prevents excessive water  Acids are proton (H+) donors
loss in the urine and increases water reabsorption
 ADH targets the kidney’s collecting ducts  Strong acids dissociate completely and liberate all of
their H+ in water

 Weak acids, such as carbonic acid, dissociate only

Small changes in electrolyte concentrations cause water partially
to move from one fluid compartment to another  Bases are proton (H+) acceptors
 A second hormone, aldosterone, helps regulate blood
composition and blood volume by acting on the kidney  Strong bases dissociate easily in water and tie up H+
 For each sodium ion reabsorbed, a chloride ion follows,  Weak bases, such as bicarbonate ion and ammonia, are
and a potassium ion is secreted into the filtrate slower to accept H+
 Water follows salt: when sodium is reabsorbed, water Molecules react to prevent dramatic changes in hydrogen
follows it passively back into the blood ion (H+) concentrations

 Bind to H+ when pH drops

Electrolyte Balance
 Release H+ when pH rises
 Renin-angiotensin mechanism
 Most important trigger for aldosterone release
 Mediated by the juxtaglomerular (JG) apparatus of the  Three major chemical buffer systems
renal tubules 1. Bicarbonate buffer system

2. Phosphate buffer system

 When cells of the JG apparatus are stimulated by low
blood pressure, the enzyme renin is released into blood 3. Protein buffer system
 Renin catalyzes reactions that produce angiotensin II
 Angiotensin II causes vasoconstriction and aldosterone The bicarbonate buffer system
release  Mixture of carbonic acid (H2CO3) and sodium
 Result is increase in blood volume and blood pressure bicarbonate (NaHCO3)

 Carbonic acid is a weak acid that does not dissociate

much in neutral or acid solutions
Maintaining Acid-Base Balance of Blood
 Bicarbonate ions (HCO3−) react with strong acids to
 Blood pH must remain between 7.35 and 7.45 to change them to weak acids
maintain homeostasis

 Alkalosis—pH above 7.45 HCl + NaHCO3 → H2CO3 + NaCl

 Acidosis—pH below 7.35 strong acid + weak base + weak acid + salt
Carbonic acid dissociates in the presence of a strong base Renal failure is an uncommon but serious problem in
to form a weak base and water which the kidneys are unable to concentrate urine, and
dialysis must be done to maintain chemical homeostasis
of blood
NaOH + H2CO3 → NaHCO3 + H2O
 With age, filtration rate decreases and tubule cells
strong base + weak acid + weak base + water
become less efficient at concentrating urine, leading to
urgency, frequency, and incontinence
 In men, urinary retention is another common problem
Respiratory mechanisms

 Respiratory rate can rise and fall depending on Problems associated with aging
changing blood pH to retain CO2(decreasing the blood  Urgency—feeling that it is necessary to void
pH) or remove CO2 (increasing the blood pH)  Frequency—frequent voiding of small amounts of urine
 Nocturia—need to get up during the night to urinate
 Incontinence—loss of control
Renal mechanisms  Urinary retention—common in males, often the result
 When blood pH rises: of hypertrophy of the prostate gland

 Bicarbonate ions are excreted

 Hydrogen ions are retained by kidney tubules

 When blood pH falls:

 Bicarbonate ions are reabsorbed

 Hydrogen ions are secreted
 Urine pH varies from 4.5 to 8.0

Developmental Aspects of the Urinary System

 The kidneys begin to develop in the first few weeks of

embryonic life and are excreting urine by the third month
of fetal life

 Common congenital abnormalities include polycystic

kidney and hypospadias

 Common urinary system problems in children and

young to middle-aged adults include infections caused by
fecal microorganisms, microorganisms causing sexually
transmitted infections, and Streptococcus

Control of the voluntary urethral sphincter does not start

until age 18 months

 Complete nighttime control may not occur until the

child is 4 years old

 Urinary tract infections (UTIs) are the only common

problems before old age

 Escherichia coli (E. coli), a bacterium, accounts for 80

percent of UTIs