This document provides an overview of the cardiovascular system, including: - The heart's structure, chambers, valves, and conduction system. - Blood flow through the heart and the events of the cardiac cycle. - Types of blood vessels and circulation (pulmonary, systemic, coronary, hepatic portal). - Functions of the cardiovascular system like oxygen transport and nutrient delivery. - Key terms like stroke volume and cardiac output.

1. Cardiovascular System
Ikramullah
Wiqarullah

2. Objectives
At the end of this session, the students will be able to:
• Describe the location, structure and functions of the
heart and its great blood vessels.
• Discuss the blood flow through the heart
• Describe the structure and functional features of the
conducting system of the heart.
• Describe the principal events of a cardiac cycle.

3. • Explain the structure and function of:
• Arteries
• Veins &
• Capillaries
• Describe the following types of blood circulation:
• Pulmonary circulation
• Systemic circulation (coronary & hepatic portal
circulation).

4. Parts of the Circulatory System
• Divided into three major parts:
– Heart
– Blood
– Blood Vessels

5. Functions of cardiovascular System
• Circulate blood throughout entire body for
– Transport of oxygen to cells.
– Transport of CO2 away from cells.
– Transport of nutrients to cells.
– Movement of immune system components. (cells,
antibodies)
– Transport of endocrine gland secretions.

6. Heart
• Location: mediastinum and rests on the diaphragm.
• Size: as much as one’s close fist.
• Weight: 250 g in adult female and 300 g in male.
• Structure: Cone shaped with pointed apex inferiorly to
left and broad base superiorly to the right.
 Membranous Layers
• Two Pericardium as superficial fibrous pericardium of
connective tissue and deeper serous pericardium of
epithelial tissue connected with the fibrous
pericardium.
• Serous pericardium—Parietal and visceral membrane.
Pericardial cavity with pericardial fluid.

7. Layers of heart
• —three layers
Epicardium or visceral layer
Myocardium—muscular layer
Endocardium—endothelial layer

8. Serous membrane
Continuous with
blood vessels

9. Chambers of the Heart
 Four chambers—two pumps
─ Two atria (superior)
─ Two ventricles (inferior)
 Right Pump
Right Atrium receives deoxygenated blood from
three veins as:
─ Superior vena cava
─ Inferior vena cava
─ Interatrial septum—between right and left atrium

10. Right Ventricle:
• Inside ridges called trabeculae carnae
• Receives blood from right atrium via tricuspid valve
(Right atrioventricular valve)
• The cusps are connected to chordae tendineae.
• Chordae tendineae are connected to papillary
muscles.
• The partition between right and left ventricle is
interventricular septum.
• Deoxygenated blood is pumped out through the
pulmonary valve (Pulmonary valve) into a large
artery called pulmonary trunk which divides into
right and left pulmonary arteries.

11. Tricuspid Valve

12. Left Pump
Left Atrium
• It receives oxygenated blood from lungs through four
pulmonary veins.
• Passes blood to the left ventricle via bicuspid (mitral)
valve or left atrioventricular valve.
Left Ventricle
• The thickest chamber of the heart.
• Forms the apex of the heart
• Blood passes from the left ventricle through the
aortic valve (aortic semilunar valve) into the
ascending aorta.
• Some blood from the ascending aorta flows into the
coronary arteries.

13. Great Blood vessels
The great blood vessels provide a pathway for the
entire cardiac circulation to proceed.
•Superior and inferior vena cava. The heart receives
relatively oxygen-poor blood from the veins of the body through
the large superior and inferior vena cava and pumps it through
the pulmonary trunk.
•Pulmonary arteries. The pulmonary trunk splits into the right
and left pulmonary arteries, which carry blood to the lungs,
where oxygen is picked up and carbon dioxide is unloaded.
•Pulmonary veins. Oxygen-rich blood drains from the lungs
and is returned to the left side of the heart through the four
pulmonary veins.
•Aorta. Blood returned to the left side of the heart is pumped out
of the heart into the aorta from which the systemic arteries
branch to supply essentially all body tissues

14. Atrioventricular valves
• The atrioventricular valves are thin, leaflike structures
located between the atria and the ventricles. The right
atrioventricular opening is guarded by the tricuspid
valve, so called because it consists of three irregularly
shaped cusps, or flaps. The leaflets consist essentially
of folds of endocardium (the membrane lining the
heart) reinforced with a flat sheet of dense connective
tissue. At the base of the leaflets, the middle
supporting flat plate becomes continuous with that of
the dense connective tissue of the ridge surrounding
the openings.

16. Semilunar valves
• They have three cusps.
• They are located at the base of both the
pulmonary trunk (pulmonary artery) and the
aorta, the two arteries taking blood out of the
ventricles.
• These valves permit blood to be forced into the
arteries, but prevent backflow of blood from the
arteries into the ventricles.
• These valves do not have chordae tendineae, and
are more similar to valves in veins than
atrioventricular valves.

17. Sound of the Heart

18. Chambers of the heart; valves

19. Valvular Disorders
• Stenosis (= narrowing): Failure of a valve to
close completely is called insufficiency or
incompetence, e.g, Mitral stenosis or aortic
stenosis in which there is backflow of blood.
• Rheumatic fever, an acute inflammatory disease
caused by streptococcal infection, is one of the
causes of valvular disorders.

20. Conduction System
• Specialized cardiac muscle fibers called
autorhythmic fibers.
• Self-excitable
• Generate electrical activity (action potential).
• No dependent on nerves for stimulation.
• Heart has its own intrinsic system.

21. Conduction System
• Cardiac muscle cells. Cardiac muscle cells can
and do contract spontaneously and independently,
even if all nervous connections are severed.
• Rhythms. Although cardiac muscles can beat
independently, the muscle cells in the different
areas of the heart have different rhythms.
• Intrinsic conduction system. The intrinsic
conduction system, or the nodal system, that is
built into the heart tissue sets the basic rhythm.
• Composition. The intrinsic conduction system is
composed of a special tissue found nowhere else in
the body; it is much like a cross between a muscle
and nervous tissue.
• Function. This system causes heart muscle
depolarization in only one direction- from the atria
to the ventricles; it enforces a contraction rate of

22. Conduction System
• approximately 75 beats per minute on the heart,
thus the heart beats as a coordinated unit.
• Sinoatrial (SA) node. The SA node has
the highest rate of depolarization in the whole
system, so it can start the beat and set the pace for
the whole heart; thus the term “pacemaker“.
• Atrial contraction. From the SA node, the impulse
spread through the atria to the AV node, and then
the atria contract.
• Ventricular contraction. It then passes through
the AV bundle, the bundle branches, and the
Purkinje fibers, resulting in
a “wringing” contraction of the ventricles that
begins at the heart apex and moves toward the
atria.
• Ejection. This contraction effectively ejects blood
superiorly into the large arteries leaving the heart.

23. The Pathway of the Conduction System
• SA node. The depolarization wave is initiated by the
sinoatrial node.
• Atrial myocardium. The wave then successively
passes through the atrial myocardium.
• Atrioventricular node. The depolarization wave
then spreads to the AV node, and then the atria
contract.
• AV bundle. It then passes rapidly through the AV
bundle.
• Bundle branches and Purkinje fibers. The wave
then continues on through the right and left bundle
branches, and then to the Purkinje fibers in the
ventricular walls, resulting in a contraction that ejects
blood, leaving the heart.

25. Heart Conduction System

26. Cardiac Cycle and Heart Sounds
In a healthy heart, the atria contract
simultaneously, then, as they start to relax,
contraction of the ventricles begin.
• Systole. Systole means heart contraction.
• Diastole. Diastole means heart relaxation.
• Cardiac cycle. The term cardiac cycle refers to
the events of one complete heart beat, during
which both atria and ventricles contract and then
relax.
• Length. The average heart beats approximately
75 times per minute, so the length of the cardiac
cycle is normally about 0.8 second.

27. Cardiac Cycle and Heart Sounds
• Mid-to-late diastole. The cycle starts with the heart in
complete relaxation; the pressure in the heart is low, and
blood is flowing passively into and through the atria into the
ventricles from the pulmonary and systemic circulations; the
semilunar valves are closed, and the AV valves are open;
then the atria contract and force the blood remaining in their
chambers into the ventricles.
• Ventricular systole. Shortly after, the
ventricular contraction begins, and the pressure within the
ventricles increases rapidly, closing the AV valves; when
the intraventricular pressure is higher than the pressure in
the large arteries leaving the heart, the semilunar valves are
forced open, and blood rushes through them out of the
ventricles; the atria are relaxed, and their chambers are again
filling with blood.

28. Cardiac Cycle and Heart Sounds
• Early diastole. At the end of systole, the
ventricles relax, the semilunar valves snap shut,
and for a moment the ventricles are completely
closed chambers; the intraventricular pressure
drops and the AV valves are forced open; the
ventricles again begin refilling rapidly with blood,
completing the cycle.
• First heart sound. The first heart sound, “lub”,
is caused by the closing of the AV valves.
• Second heart sound. The second heart
sound, “dub”, occurs when the semilunar valves
close at the end of systole.

29. Cardiac Output
• Cardiac output is the amount of blood pumped out
by each side of the heart in one minute. It is the product of
the heart rate and the stroke volume.
• Stroke volume. Stroke volume is the volume of blood
pumped out by a ventricle with each heartbeat.
• Regulation of stroke volume. According to Starling’s law
of the heart, the critical factor controlling stroke volume is
how much the cardiac muscle cells are stretched just before
they contract; the more they are stretched, the stronger the
contraction will be; and anything that increases the volume
or speed of venous return also increases stroke volume and
force of contraction.
• Factors modifying basic heart rate. The most important
external influence on heart rate is the activity of the
autonomic nervous system, as well as physical
factors (age, gender, exercise, and body temperature).

30. Blood Vessels
• Blood circulates inside the blood vessels, which
form a closed transport system, the so-called
vascular system.
• Arteries. As the heart beats, blood is propelled
into large arteries leaving the heart.
• Arterioles. It then moves into successively
smaller and smaller arteries and then into
arterioles, which feed the capillary beds in the
tissues.
• Veins. Capillary beds are drained by venules,
which in turn empty into veins that finally empty
into the great veins entering the heart.

31. Tunics

32. Tunics
• Tunica intima. The tunica intima, which lines the
lumen, or interior, of the vessels, is a thin layer of
endothelium resting on a basement membrane and
decreases friction as blood flows through the vessel
lumen.
• Tunica media. The tunica media is the bulky middle
coat which mostly consists of smooth muscle and
elastic fibers that constrict or dilate, making the blood
pressure increase or decrease.
• Tunica externa. The tunica externa is the outermost
tunic composed largely of fibrous connective tissue,
and its function is basically to support and protect the
vessels.

33. Major Arteries of the Systemic Circulation
Arterial Branches of the Ascending Aorta
• The aorta springs upward from the left ventricle of
heart as the ascending aorta.
• Coronary arteries. The only branches of the
ascending aorta are the right and left coronary
arteries, which serve the heart.
• Arterial Branches of the Aortic Arch
• The aorta arches to the left as the aortic arch.
• Brachiocephalic trunk. The brachiocephalic trunk,
the first branch off the aortic arch, splits into
the right common carotid artery and right
subclavian artery.

34. Major Arteries of the Systemic Circulation
• Left common carotid artery. The left common carotid
artery is the second branch off the aortic arch and it
divides, forming the left internal carotid, which serves
the brain, and the left external carotid, which serves
the skin and muscles of the head and neck.
• Left subclavian artery. The third branch of the aortic
arch, the left subclavian artery, gives off an important
branch- the vertebral artery, which serves part of the
brain.
• Axillary artery. In the axilla, the subclavian artery
becomes the axillary artery.
• Brachial artery. the subclavian artery continues into
the arm as the brachial artery, which supplies the arm.
• Radial and ulnar arteries. At the elbow, the brachial
artery splits to form the radial and ulnar arteries, which
serve the forearm.

36. Arterial Branches of the Thoracic Aorta
• The aorta plunges downward through the thorax,
following the spine as the thoracic aorta.
• Intercostal arteries. Ten pairs of intercostal arteries
supply the muscles of the thorax wall.
Arterial Branches of the Abdominal Aorta
• Finally, the aorta passes through the diaphragm
into the abdominopelvic cavity, where it
becomes the abdominal aorta.
• Celiac trunk. The celiac trunk is the first branch
of the abdominal aorta and has three branches:
the left gastric artery supplies the stomach;
the splenic artery supplies the spleen, and
the common hepatic artery supplies the liver.

37. Arterial Branches of the Abdominal
Aorta
• Superior mesenteric artery. The unpaired superior
mesenteric artery supplies most of the small intestine
and the first half of the large intestine or colon.
• Renal arteries. The renal arteries serve the kidneys.
• Gonadal arteries. The gonadal arteries supply the
gonads, and they are called ovarian arteries in females
while in males they are testicular arteries.
• Lumbar arteries. The lumbar arteries are several pairs
of arteries serving the heavy muscles of the abdomen
and trunk walls.
• Inferior mesenteric artery. The inferior mesenteric
artery is a small, unpaired artery supplying the second
half of the large intestine.
• Common iliac arteries. The common iliac arteries are
the final branches of the abdominal aorta.

38. Veins Draining into the Superior Vena Cava
• Veins draining into the superior vena cava are
named in a distal-to-proximal direction; that is, in
the same direction the blood flows into the superior
vena cava.
• Radial and ulnar veins. The radial and ulnar
veins are deep veins draining the forearm; they
unite to form the deep brachial vein, which drains
the arm and empties into the axillary vein in the
axillary region.
• Cephalic vein. The cephalic vein provides for the
superficial drainage of the lateral aspect of the arm
and empties into the axillary vein.
• Basilic vein. The basilic vein is a superficial vein
that drains the medial aspect of the arm and
empties into the brachial vein proximally.

39. Veins Draining into the Superior Vena Cava
• Median cubital vein. The basilic and cephalic veins are
joined at the anterior aspect of the elbow by the median
cubital vein, often chosen as the site for blood removal for the
purpose of blood testing.
• Subclavian vein. The subclavian vein receives venous blood
from the arm through the axillary vein and from the skin and
muscles of the head through the external jugular vein.
• Vertebral vein. The vertebral vein drains the posterior part of
the head.
• Internal jugular vein. The internal jugular vein drains the
Dural sinuses of the brain.
• Brachiocephalic veins. The right and left brachiocephalic
veins are large veins that receive venous drainage from the
subclavian, vertebral, and internal jugular veins on their
respective sides.
• Azygos vein. The azygos vein is a single vein that drains the
thorax and enters the superior vena cava just before it joins
the heart.

41. Veins Draining into the Inferior Vena Cava
• The inferior vena cava, which is much longer than
the superior vena cava, returns blood to the heart
from all body regions below the diaphragm.
• Tibial veins. The anterior and posterior tibial
veins and the fibular vein drain the leg;
the posterior tibial veins becomes the popliteal
vein at the knee and then the femoral vein in the
thigh; the femoral vein becomes the external
iliac vein as it enters the pelvis.
• Great saphenous veins. The great saphenous
veins are the longest veins in the body; they
begin at the dorsal venous arch in the foot and
travel up the medial aspect of the leg to empty
into the femoral vein in the thigh.

42. Veins Draining into the Inferior Vena Cava
• Common iliac vein. Each common iliac vein is
formed by the union of the external iliac vein and
the internal iliac vein which drains the pelvis.
• Gonadal vein. The right gonadal vein drains the
right ovary in females and the right testicles in
males; the left gonadal veins empties into the left
renal veins superiorly.
• Renal veins. The right and left renal veins drain
the kidneys.
• Hepatic portal vein. The hepatic portal vein is a
single vein that drains the digestive tract organs
and carries this blood through the liver before it
enters the systemic circulation.
• Hepatic veins. The hepatic veins drain the liver.

43. CORONARY CIRCULATION
• Heart is supplied by TWO CORONARY arteries:
1- Left coronary artery---(LCA)
2- Right coronary artery---(RCA)
• These coronary arteries arise at the root of
the aorta.
43

44. Coronary arteries & their branches
LCA---- it passes under the left atrium and divides
into two branches:
1. Left Anterior Descending (LAD)
• It gives off smaller branches to the interventricular
septum and anterior walls of both ventricles.
2. Circumflex Artery
• It continues around the left side of the heart and
supplies blood to the left atrium and posterior wall
of the left ventricle.
44

45. Coronary arteries
RCA ---- It gives off two branches:
1. Marginal Artery
• It supplies blood to the lateral aspect of the
right atrium and ventricle.
2. Posterior descending artery
• It supplies blood to the posterior walls of both
ventricles.
45

46. Diagram of coronary circulation
46

47. Coronary Arteries

48. Venous return of Heart
Most of the venous blood return to heart occurs
through the coronary sinus and anterior cardiac
veins, which drain into the right atrium
48

49. Blood flow to Heart during Systole & Diastole
• During systole when heart muscle contracts it
compresses the coronary arteries therefore
blood flow is less to the left ventricle during
systole and more during diastole.
• To the subendocardial portion of Left ventricle it
occurs only during diastole
49

50. 50

51. 51
Special features of veins
• Valves
– Prevent backflow
– Most abundant in legs (where blood
has to travel against gravity)
• Muscular contraction
– Aids the return of blood to heart in
conjunction with valves

52. 52
Exercise helps
circulation
(because
muscles
contract and
squeeze blood
back to the
heart)

53. 53
Vascular System
(Blood vessels of the body)
• Two circulations
– Systemic
– Pulmonary
• Arteries and veins usually run together
• Often nerves run with them

54. 54
Pulmonary Circulation
• Pulmonary trunk branches
– Right and left pulmonary arteries
– Division into lobar arteries
• 3 on right
• 2 on left
– Smaller and smaller arterioles, into capillaries surrounding alveoli
• Gas exchange

55. 55
Pulmonary Circulation
• After gas exchange blood enters venules
• Larger and larger into Superior and Inferior Pulmonary
veins
• Four Pulmonary Veins empty into left atrium

56. 56

57. 57
Systemic Circulation
• Oxygenated blood to body
• Leaves LV through Ascending Aorta
– Only branches are the 2 coronary arteries to the heart
• Aortic Arch has three arteries branching from it:
1. Brachiocephalic trunk, has 2 branches:
• Right common carotid a.
• Right subclavian a.
2. Left common carotid a.
3. Left subclavian a.
Ligamentum arteriosum
connecting to pulmonary a.

58. 58
• Hepatic portal system
– Picks up digested nutrients from stomach & intestines and
delivers them to liver for processing and storage
• Storage of nutrients
• Detoxification of toxins, drugs, etc.
Tributaries of hepatic
portal vein:
-superior mesenteric vein
-splenic vein
-inferior mesenteric vein

59. 59

60. References:
• Gerard J, Tortora/Brayan Derrickson edition
2016.