THE CIRCULATORY SYSTEM

LEARNING OUTCOMES
At the end of this lesson, the students must be able to:
1. Distinguish the layers and other structures of the heart and give their
functions;
2. Cite the disorders and diagnostic tests of the circulatory system;
3. Identify the two main divisions of the vascular system, describe the
function of each, and trace the flow of blood throughout the system;
4. Point out the different types of blood vessels and describe the structure
and functions of each;
5. Enumerate the major constituents of blood and describe the function of
each of the formed elements;
6. Differentiate serum, plasma, and whole blood;
7. Describe the vessels, structure, and functions of the lymphatic system;
8. Define hemostasis and explain the basic coagulation and fibrinolysis
processes; and
9. Specify and locate major veins in the arms and legs and discuss the
sustainability of each for venipuncture.
THE CIRCULATORY SYSTEM
- transports the oxygenated blood from the heart and
lungs all throughout the body thru the arteries, and then
the oxygen depleted blood is returned to its origin thru
the help of the veins.
- helps in the coagulation process, regulates the body
temperature and assists the body in fighting diseases.
- two main components: the Cardiovascular system and
the Lymphatic system.
THE LAYERS, STRUCTURES OF THE HEART AND
THEIR FUNCTION
- hollow muscular organ
- four chambers (left atrium, right atrium, left ventricles,
and right ventricles)
- surrounded by pericardium (thin, fluid-filled sac)
- about the same size as of a man's clenched fist
Layers of the heart
1. Epicardium - thin, watery membrane in the outer
layer of the heart.
Function: covers the heart and attached to the
pericardium.
2. Myocardium - thick layer of cardiac muscles in the
middle layer of the heart.
Function: pumps blood to the arteries by contracting.
3. Endocardium - thin layer of epithelial cells in the
inner layer of the heart.
Function: lines the valves and interior chambers.
Chambers of the heart
1.Right Atrium - upper right chamber
Function: Receives deoxygenated blood from the
body.

2.Right Ventricle - lower right chamber

Function: Receives the blood from the right atrium
and pumps into pulmonary artery.
Chambers of the heart (Continuation)
3.Left Atrium - upper left chamber
Function: Receives oxygenated blood from the lungs
and pumps it into the left ventricle.

4.Left Ventricle - lower left chamber

Function: Receives blood from the left atrium and
pumps it into the aorta.
Valves of the heart
1. Right AV valve - tricuspid valve which is located
between the right atrium and right ventricle.
Function: Closes as the right ventricles contracts
preventing blood from flowing back to the right atrium.

2. Left AV valve - bicuspid or mitral valve which is located

between the left atrium and left ventricle.
Function: Closes as the left ventricles contracts
preventing blood from flowing back to the left atrium.
Valves of the heart
3. Right semilunar valve - pulmonary or pulmonic valve
located at the entrance of the pulmonary artery.
Function: Closes when the right ventricle relaxes
preventing blood from flowing back to the right
ventricle.

4. Left semilunar valve - aortic valve located at the

entrance of the aorta.
Function: Closes when the left ventricle relaxes
preventing blood from flowing back to the left ventricle.
Septa
1. Interatrial septum - partition that separates the right
from the left atria.
2. Interventicular septum - separates the right and the
left ventricles.

Coronary Circulation
- The heart receives blood supply thru the left and right
coronary arteries, and coronary veins return the oxygen
depleted blood from the heart muscle back to the heart.
Heart function
- the Coronary circulation supplies the blood and also
provides drainage from the tissues.
- composed of the left and right coronary arteries and
coronary veins.
- Poor circulation could lead to Ischemia which is caused
by inadequate supply of oxygen and Myocardial
infraction or heart attack
 Figure 3.1 The Blood Flow of the Human Heart
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 Functions of the heart
Function Description
Cardiac Cycle Systole (contraction) & diastole (relaxation) which lasts about 0.8
seconds
Electrical conduction system Sends electric impulses throughout the myocardium which is
initiated by the Sinoatrial (SA) node (pacemaker)
Electrocardiogram (ECG) Provides the graphical representation of the cardiac cycle's activity
Origin of heart sounds "lubb" which is the first sound as the ventricles contract or the AV
valves close and "dupp" or the second sound which is heard when
the semilunar valves close and the ventricles relax.

Heart rate & cardiac output The average heart rate is 72 beats per minute (bpm) and the cardiac
output refers to the volume of blood pumped per minute
Pulse A rhythmic throbbing resulting from the alternating expansion and
contraction of the artery
Blood pressure The force which was exerted by the blood on the walls of the vessel
which is measured by the sphygmomanometer. The blood pressure is
the difference between the systolic (pressure during contraction)
and diastolic (pressure during relaxation).
DISORDERS AND DIAGNOSTICS TESTS OF THE
CIRCULATORY SYSTEM
The human heart may have disorders which can be
detected and addressed using the proper diagnostic tests:
1.Angina pectoris - chest pain resulting from reduced
blood flow to the heart.
2.Aortic stenosis - a murmur sound produced when the
aortic leaflets fail to fully open during systole.
3.Bacterial endocarditis - an infection that happens
when a bacteria enters and resides in the heart lining
or blood vessel.
DISORDERS AND DIAGNOSTICS TESTS OF THE
CIRCULATORY SYSTEM
4.Congestive heart failure - results to general feeling or
weakness due to insufficient blood being pumped by
the heart.
5.Myocardial infarction - known as heart attack due to
decrease or full stoppage of blood flow that damages
the heart muscle.
6.Pericarditis - inflammation of the pericardial sac that
maybe due to viral infection
List of diagnostic tests for heart disorders:
 Arterial Blood Gases (ABG)
 Aspartate aminotransferase (AST) or Serum glutamic-
oxaloacetic transaminase (SGOT)
 Cholesterol
 Creatine kinase (CK)
 Creatine Kinase (CK)-MB
 Digoxin
List of diagnostic tests for heart disorders: (Continuation)
 Electrocardiogram (ECG or EKG)
Lactate dehydrogenase (LD) isoenzymes
 Microbial cultures
 Myoglobin
 Potassium (K)
 Triglycerides
 Troponin T (TnT)
TWO MAIN DIVISIONS AND FUNCTIONS OF THE
VASCULAR SYSTEM

Vascular System - the loop which consists of a system

of blood vessels through which blood is circulated to the
rest of the body.
• two divisions:
(1) pulmonary circulation and
(2) systemic circulation
TWO MAIN DIVISIONS AND FUNCTIONS OF THE
VASCULAR SYSTEM
The pulmonary circulation moves the blood between the
right ventricle of the heart to the lungs.
During the process, oxygen is absorbed and carbon dioxide
is released, after which, the oxygenated blood flows back
to the left atrium of the heart. The systematic circulation
moves the oxygenated blood and nutrients from the left
ventricle of the heart to the rest of the body. The
deoxygenated blood with carbon dioxide & wastes flows
back to the right atrium.
 Figure 3.2 The Pulmonary and Systemic Circulation
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Structure of the Vascular System
a) Arteries - thick-walled blood vessels that carry oxygen-
rich blood from the heart to the tissues of the body.
b) Arterioles - a small-diameter blood vessel that branches
out from the arteries and leads to the capillaries.
c) Veins - tubes with thin walls that carry deoxygenated
blood from tissues to the heart.
d) Venules - a very small vein that collects blood from the
capillaries.
e) Capillaries - fine hair-like blood vessels that connect
arterioles and veins.
 Figure 3.3 Venous and arterial system
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TYPES, STRUCTURES AND FUNCTIONS OF BLOOD VESSELS
Blood vessel structure
A. Layers
• tunica adventitia (outer connective tissue),
• tunica media (middle, muscle and elastic fiber), and
• tunica intima (inner, endothelial cells)
B. Lumen- - space inside the blood vessel where the
blood flows.
C. Valves- - found in the veins, thin membranous leaflets
that prevent backflow of blood.
THE FLOW OF BLOOD
• Oxygen-poor blood is returned to the heart thru the superior and
inferior venae cavae and it enters the right atrium of the heart.
• The right atrium contracts, pushing blood through the tricuspid valve,
and into the right ventricle.
• The contraction on the right ventricle forces the blood to the
pulmonary semilunar valve into the pulmonary artery.
• It flows through the pulmonary artery to the capillaries of the lungs.
• Oxygen-rich blood flows back to the heart thru the pulmonary veins
and enters the left atrium.
• The left atrium contracts forcing the blood in the bicuspid valve into
the left ventricle.
THE FLOW OF BLOOD (Continuation…)
• The contraction of the left ventricle forces the blood through the
aortic semilunar valve to the aorta.
• The blood travels through the body by the way of the arteries. They
branch into smaller arteries and the smallest of which are the
arterioles.
• The arterioles connect with the capillaries. Oxygen, water, and
nutrients from the blood are diffused through the capillary walls to
the cells and carbon dioxide and other end product enters the
bloodstream.
• The capillaries connect with the venules.
• The venules merge into larger veins until the blood returns to the
heart by thru the superior or inferior vena cava.
 Click to
view the
Augmented
Reality of
the Heart:
Disorders of the vascular system
1. Aneurysm - an enlargement of the artery due to the weakening of
the artery wall.
2. Arteriosclerosis- hardening of the artery wall due to aging.
3. Atherosclerosis-formation of plaques in the inner walls.
4. Embolism - clot or bubble which causes obstruction of an artery.
5. Embolus- obstruction that is carried and lodged in a vessel.
6. Hemorrhoids- swollen veins in the area of the anus.
7. Phlebitis- inflammation of the veins particularly the wall.
8. Thrombophlebitis- swelling of the veins of the legs that usually
occurs during pregnancy.
9. Thrombus- blood clot that impedes blood flow.
10.Varicose Veins- usually found in the legs, these are veins that have
been twisted and have enlarged.
Diagnostic Test of the vascular system
 D-Dimer
 Fibrin degradation products (FDP)
 Lipoproteins
 Prothombin time (PT)
 Partial thromboplastin time (PTT/APTT)
 Triglycerides
MAJOR CONSTITUENTS AND FUNCTIONS OF BLOOD CELLS

The blood is the red fluid that is transported throughout the

body through the circulatory system.

There are two functions:

1. Arterial blood
2. Venous blood
 Figure 3.5 Composition of the Blood
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HUMAN BLOOD
• Composed of plasma and other formed elements.
• Contains gases (02, CO2, N), minerals (Na, K, Ca, Mg), carbs & lipids,
proteins, etc.

Plasma - a clear, straw-colored liquid portion of the blood which is 90% water.

Three components:
1. Erythrocytes (red blood cells)
2. Leukocytes (white blood cells)
3. Thrombocytes (platelets)
Blood type
• The human blood type is inherited and determined by the antigens on the
surface of the red blood cells.
• The blood contains or can develop antibodies directed at the opposite blood
type.
• Blood type match is important especially during blood transfusion because
the wrong type could agglutinate the red blood cells. When a doctor
mentions blood type, he is referring to your or ABO system or Rhesus (RH)
factor.
ABO blood group system
• System of classifying human blood by the presence of antigens A and B and
based on the antigenic components found on the surface of the red blood
cells.
• Patient's blood could be classified as A, B, O, or AB (universal patients).
RH blood-group system
• system of classification of primary importance in obstetrics because of the
hemolytic disease of the newborn (HDN).
• based on the "D" antigen or the Rh factor. Rh positive (Rh+) have red blood
cells that have the D antigen while the Rh negative (Rh -) does not have the
D antigen.
• Compatibility and cross-match is necessary to determine the compatibility of
the donor and recipient's blood because an individual who do not produce
the D antigen will produce anti-D which could be fatal if they encounter the
D antigen.
 Figure 3.6 ABO System Blood Types
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WHOLE BLOOD, SERUM AND PLASMA
There are three blood specimen that are collected for testing
purposes:
1. Serum
2. Plasma
3. The whole blood
Blood disorders
1. Anemia- caused by not having enough healthy red blood cells or
hemoglobin.
2. Leukemia - cancer of the blood forming tissues like the bone marrow or the
lympathic system.
3. Leukocytes - high number could indicate urinary tract infection.
4. Leukocytosis - increase of the number of white blood cells in the blood due
to illness or infection.
5. Leukopenia - reduced number of white cells in the blood.
6. Polycythemia - the marrow produces too many red blood cells resulting to
blood thickening.
7. Thrombocytosis - the body produces too many platelets (thrombocytes)
which affects the blood clotting.
8. Thrombocytopenia - characterized by low platelet count.
Diagnostic Test for blood disorders
 ABO & RH type
 Bone marrow examination
 Complete Blood Count (CBC)
 Cross-match
 Differential (diff)
 Eosinophil (Eos) count
 Erythrocyte sedimentation rate (ESR)
 Ferritin
 Hematocrit (Hct)
 Hemoglabin (Hb or Hgb)
 Hemogram
 Indices (MCH, MCV, MCHC)
 Iron (Fe)
 Reticulocyte (retic) count
 Total iron-b-nding capacity (TIBC)
STRUCTURE AND FUNCTION OF THE LYMPHATIC SYSTEM
The lymphatic system of the human body is a network of tissues and organs
that is responsible for the removal of toxins and waste in the body.
Primary function:
The main function is to transport the white blood cells to and from the lymph
nodes throughout the body.
Structure of the Lymphatic System
o The Lymphatic System is composed of fluids or lymph which is similar to
plasma but is composed of 95% water.
o The lymph is transported throughout the system thru the lymphatic vessels,
ducts and masses of lymph tissue called nodes.
 Figure 3.8 The Lymphatic System
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Functions of the Lymphatic System
Aside from the transporting the white blood cells to and from the
lymph nodes, the Lymphatic System has other functions:
(1) transport back the tissue fluids to the bloodstream,
(2) removes impurities,
(3) processes lymphocytes and
(4) transport the fats absorbed from the small intestine into the bloodstream.
The Lymph, an excess tissue fluid that filters into lymphatic capillaries.
The Capillaries are joined and forms the larger vessels which empties into the
right lymphatic duct and thoracic duct which empties into the larger veins of
the upper body.
Disorders of the Lymphatic System
1. Lymphangitis - inflammation of lymphatic channels resulting from an
infection at a site distal to the channel.
2. Lymphadenitis - refers to the inflammation of the lymph nodes.
3. Lymphadenopathy - also called adenopathy, a disease where there is
abnormality in the size or number of lymph nodes.
4. Splenomegaly - enlargement of the spleen.
5. Hodgkin's disease - cancer on the part of the immune system characterized
by enlarged lymph nodes.
6. Lymphosarcoma - a type of cancer that develops from lymphocytes.
7. Lymphoma - cancer that begins with the lymphocytes.
Diagnostic Test for the Lymphatic System disorder
 Bone marrow biopsy
 Complete Blood Count
 Culture & Sensitivity
 Lymph node biopsy
 Mononucleosis test
HEMOSTASIS, BASIC COAGULATION AND FIBRINOLYSIS PROCESSES
Hemostasis is the stoppage of bleeding as a response to an injury
whether it be normal vasoconstriction where the vessel walls close temporarily,
abnormal obstruction like plaque or by coagulation such as litigation.
There are four interrelated responses:
1. Vasoconstriction - the vessel walls are constricted after an injury which
results to reduced flow of flood in the site of injury.
2. Formation of the primary platelet plug - platelets stick together on the
site of the injury forming as plug.
3. Progression to the stable blood clot
4. Fibrinolysis or dissolving of clot
Coagulation factors and pathways
Coagulation or clotting is the process where the blood changes from a
liquid form into a gel that forms the blood clot.
There are three types:
1. Enzyme precursors,
2. Cofactors, and
3. Substrates
Pathways of the clotting cascade:
1. Extrinsic pathway
2. Intrinsic pathway
Phases of cell-based coagulation:
1. Initiation
2. Amplification, and
3. Propagation
Role of the thrombin
• Thrombin is an enzyme that plays an important role in coagulation.
• It amplifies coagulation and converts fibrinogen to soluble fibrin.
• This supports the platelet plug formation by activating factor XIII to
cross-link fibrin and also controls the formation & coagulation process
by activating protein C.
Vasoconstriction Platelet Plug formation
• due to contraction of smooth • The initiation phase
muscle fibers
• Decrease blood flow and limits
blood lost
• reduces diameter of blood vessel

Secondary hemostatic plug

formation
• Amplification
• Propagation
Fibrinolysis
Fibrinolysis is the process where the fibrin is dissolved. It has two
main activities:
(1) the intact vessels are reopened by dissolving the clots, and
(2) removing hemostatic clots from the tissue as part of the healing process.
The role of the liver in hemostasis
• The liver’s role in the hemostasis is to synthesize coagulation factors
such as V, VIII, prothrombin, & fibrogen.
• This organ produces heparin and bile salts needed for synthesis.
• It is also responsible for the production of bile salts needed for vitamin K
absorption.
Hemostatic Disorders
1. Deep venous thrombosis (DVT) - happens when blood clot forms in one or
more deep veins, usually in the legs.
2. Disseminated intravascular coagulation - when the formation of small clots
blocks the small blood vessels.
3. Hemophilia - disorder involving lack of sufficient blood-clotting proteins.
4. Thrombocytopenia - low platelet count
Diagnostic Test for Hemostatic disorders
 Bleeding time
 D-dimer
 Factor assays
 Fibrin degradation products (FDP)
 Platelet function assay (PFA)
 Prothrombin time (PT)
 Partial thromboplastin time (PTT or APTT)
MAJOR ARM AND LEG VEINS IN VENIPUNCTURE

A.Antecubital fossa
• also called the elbow pit is a triangular area on
the anterior of the elbow.
• the first-choice for venipuncture site because
there are several major arm veins called
antecubital veins which are close to the surface
which makes it easy to locate and penetrate.
B.H-Shaped antecubital veins - a vein arrangement
that occurs in about 70% of the population.
• Median cubital vein - preferred venipuncture
site; easiest to access and least painful;
• Cephalic Vein - second choice in venipuncture
site; harder to palpate; only available site for
obese patients;
• Basilic vein - last choice vein in vebipuncture;
not well anchored; punctures are more painful;
C.M-Shaped antecubital veins - the intermediate
antebrachial vein and involves the median,
median cephalic and median basilic veins.
• Median vein - intermediate antebrachial vein;
first-choice vein; safest and less painful;
• Median cephalic vein - intermediate cephalic
vein; second choice in venipuncture site; less
likely to roll;
• Medial basilic vein - intermediate basilic vein;
last choice vein because although it is more
painful;
D. Other arm and hand veins - used only if the antecubital veins are not
accessible. The veins at the back of the hand which can be used are
smaller, so it may be very painful. Take note that the underside of the wrist
is never used as a venipuncture site.
E.Leg, ankle and foot veins - must not be used in
venipuncture with the permission of a physician
due to complications such as thrombosis.
F. Arteries - not used for routine blood collection
and limited to collection of arterial blood gas.
Special training is needed and it is more risky for
the patient.