The document provides an overview of the cardiovascular system, including: - The heart's structure, chambers, valves, and conduction system. - Blood flow through the heart in a cardiac cycle, including systole and diastole of the atria and ventricles. - Major blood vessels like arteries, veins, and capillaries. Pulmonary and systemic circulation are described. - Coronary circulation which supplies blood to the heart muscle is explained in detail. Common cardiovascular diseases like coronary artery disease and myocardial infarction are also summarized.

1. Cardiovascular System
Muhammad Iqbal
Lecturer
KMU
A&P-I Unit VIII
1

2. Objectives
At the end of this session, the students will be able to:
• Define blood and list its functions
• Describe the composition, sites of production and
functions of cellular parts of blood and plasma
• Briefly explain the ABO blood groups & Rh factor.
• 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. 2

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

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

5. Functions of C-V 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
5

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.
• —three layers
1. Outer Pericardium—membranous layer
2. Middle Myocardium—muscular layer
3. Inner Endocardium—endothelial layer
6

7. Layers of heart
 Membranous Layers
• Two Pericardiums 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.(balloon eg)
• Pericardial cavity with pericardial fluid-----25 to 35 ml
 Myocardium
i. Pacemaker
ii. Conductive system
iii. Contractile muscle fibers
7

8. Serous membrane
Continuous with
blood vessels
8

9. Actions of the Heart
• Actions of the heart are classified into four types:
1. Chronotropic action----Heart Rate
2. Inotropic action.......Force of contraction
3. Dromotropic action.......Conduction of impulse
(Speed)
4. Bathmotropic action.......Excitability of muscles
9

10. 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
─ Coronary sinus
• Interatrial septum—between right and left atrium
10

11.  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 (p. semilunar valve) into a large
artery called pulmonary trunk which divides into right
and left pulmonary arteries.
11

12. 12

13. 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

14. 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.
14

15. Tricuspid Valve
15

16. 16

17. • The “ lub” is the first heart sound, commonly
termed S1, and is produced by turbulence
caused by the closure of mitral and tricuspid
valves at the start of systole. The second
sound,” dup” or S2, is caused by the closure of
aortic and pulmonic valves, marking the end
of systole.
17

18. Chambers of the heart; valves
18

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.
• Mitral Valve Prolapse (MVP): The protrusion of
one or both cusps of the mitral valve into the
left atrium during ventricular contraction.
• Rheumatic fever, an acute inflammatory disease
caused by streptococcal infection, is one of the
causes of valvular disorders.
19

20. Conduction System
• Specialized cardiac muscle fibers called
autorhythmic fibers.
• Self-excitable
• Generate electrical activity (action potential).
• Not dependent on nerves for stimulation.
• Heart has its own intrinsic system.
• Syncytium (atrioventricular) acts like a single unit
20

21. These muscle fibers have two important functions
1. Act as a pacemaker (setting the rhythm of electrical
excitation that causes the contractions)
2. Form the conduction system (a network of specialized
cardiac muscle fibers)
• The conduction system occurs as follows:
1. Sinoatrial (SA) node, located in the right atrial wall
just inferior and lateral to the opening of the superior
vena cava, generate electrical signals.
2. After atrial contraction the action potential reaches
the atrioventricular (AV) node, located in the interatrial
septum just anterior to the opening of the coronary
sinus.
3. From the AV node, the action potential enters the
atrioventricular (AV) bundle (also known as bundle of His)
21

22. 4. The AV bundle divides into right and left bundle
branches and extending via interventricular
septum toward the heart apex.
5. The right and left bundle branches finally divide
into Purkinji fibers that conduct the action
potential upward to the remaining of the
ventricles.
22

23. Conduction System
23

24. Heart Conduction System
24

25. Cardiac Cycle
Cardiac cycle consists of systole and diastole of atria
and ventricles
Atrial Systole (Atrial contraction):
• Lasts about 0.1 sec
• At the same time, the ventricles are relaxed
• Depolarization of the SA node causes atrial
depolarization which is marked by P wave in the
ECG.
• Atrial depolarization causes atrial systole.
• Blood is forced via AV valves into the ventricles.
25

26. Cardiac Cycle cont…
• Atrial systole contributes 25 ml of blood to the
volume of 105 ml already in each ventricle.
• At the end of ventricular diastole, each ventricle
has about130 ml.
• This blood volume (120—130 ml) is called end-
diastolic volume (EDV).
• The QRS complex in the ECG marks the onset of
ventricular depolarization.
• The percentage of the EDV ejected (about 60%)
is ejection fraction.
26

27. Ventricular Systole:
• It lasts about 0.3 sec
• At the same time, the atria are relaxed.
• Ventricular depolarization causes ventricular systole.
• The T wave in the ECG marks the onset of ventricular
repolarization.
• The right and left ventricles eject about 70 ml of blood
each into the pulmonary trunk and aorta respectively.
• The blood volume remaining in each ventricle at the
end of systole, about 60 ml, is the end-systolic volume
(ESV).
• Stroke volume (the volume ejected per beat by each
ventricle) equals EDV minus ESV (SV=EDV—ESV ). 27

28. • Cardiac Output: The amount of blood ejected by
each ventricle in one minute is called cardiac
output (CO).
• Cardiac output = Heart rate × Stroke volume
• Pre-load:
• Degree of tension on muscle when it begins to
contract.
• Pre-load = end-diastolic pressure
• After-load: Load against which muscle exerts its
contractile force.
• After-load = pressure in aorta and pulmonary trunk
28

29. CORONARY CIRCULATION
• Heart is supplied by TWO CORONARY arteries:
1- Right coronary artery---(RCA)
2- Left coronary artery---(LCA)
• These coronary arteries arise at the root of
the aorta.
29

30. Coronary arteries & their branches
 LCA---- it passes under the left atrium and divides into
two branches:
1. 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.
2. Left Anterior Descending (LAD)
• It gives off smaller branches to the interventricular
septum and anterior walls of both ventricles.
30

31. Coronary arteries cont…
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.
31

32. Coronary Arteries (Anterior view)
32

33. Coronary Arteries (posterior view)
33

34. 34

35. • 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
35

36. 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
36

37. • As we know blood flow to subendocardial
surface of left ventricle during systole is not
there, therefore, this region is prone to
ischemic damage and most common site of
Myocardial infarction.
37

38. • Coronary blood flow to the right side is
not much affected during systole.
Reason---Pressure difference between
aorta and right ventricle is greater during
systole than during diastole, therefore
more blood flow to right ventricle occurs
during systole.
38

39. CORONARY ARTERY DISEASE
• Ischemic heart disease (IHD) (angina pectoris)
• Myocardial Infarction
• Angina pectoris:
– there is reduced coronary artery blood flow due to
atherosclerosis (cholestrol deposition -- Plaque)
39

40. CAUSES OF IHD:
–Cigarette smoking
–Hypertension
–Diabetes mellitus
–Increased lipids ( cholesterol)
–Other factors: lack of exercise, anxiety etc.
40

41. MYOCARDIAL INFARCTION (MI):
– it is due to obstruction to the coronary blood flow, at
least 75 % of lumen of coronary artery is blocked by
thrombus.
– MI is the common cause of death.
41

42. 42

43. 43

44. 44
3 Major types of blood
vessels
• Body
• RA
• RV
• Lungs
• LA
• LV
• Boby
1.Arteries
2.Capillaries
3.Veins
Arteries carry blood away from the heart
-”branch,” “diverge” or “fork”
Veins carry blood toward the heart
-”join”, “merge,” “converge”

45. 45
General characteristics of vessels
• Three layers (except for the smallest)
1. Tunica intima
2. Tunica media
3. Tunica externa or adventitia
• Lumen is the central blood filled space

46. 46
• Intima is endothelium (simple squamous epithelium)
• Tunica media: layers of circular smooth muscles
– Lamina (layers) of elastin and collagen internal and external
– Thicker in arteries than veins (maintain blood pressure)
Smooth muscle
contraction:
vasoconstriction
Smooth muscle
relaxation:
vasodilation

47. 47
• Adventitia (t. externa) – longitudinally running
collagen and elastin for strength and recoil

48. 48
Capillaries
Heart to arteries to capillaries to veins to heart
• Capillaries are smallest
– 8-10um
– Just big enough for single file erythrocytes
– Composed of: single layer of endothelial cells surrounded by
basement membrane
• Universal function
– Oxygen and nutrient delivery to tissues
– CO2 and nitrogenous waste removal
• Some also have tissue specific functions

49. 49
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

50. 50
Exercise helps
circulation
(because
muscles
contract and
squeeze blood
back to the
heart)

51. 51
Vascular System
(Blood vessels of the body)
• Two circulations
– Systemic
– Pulmonary
• Arteries and veins usually run together
• Often nerves run with them

52. 52
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

53. 53
Pulmonary Circulation
• After gas exchange blood enters venules
• Larger and larger into Superior and Inferior Pulmonary
veins
• Four Pulmonary Veins empty into left atrium

54. Aorta
54

55. 55

56. 56

57. Nine common sites of Pulse
• The pulse may be palpated in any place that
allows an artery to be compressed near the
surface of the body, such as at the neck
(carotid artery), wrist (radial artery), at the
groin (femoral artery), behind the knee
(popliteal artery), near the ankle joint
(posterior tibial artery), and on foot (dorsalis
pedis artery).
57

58. 58

59. 59

60. 60

61. 61