1.
Cardiovascular System
Tariq Siraj Qazi
Assistant Professor/ Principal
JCN Abbottabad
A&P-I Unit VIII

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.

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).

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

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

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 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.
• Pericardial cavity with pericardial fluid.

7.
Layers of heart
• —three layers
1. Outer Pericardium—membranous layer
2. Middle Myocardium—muscular layer
3. Inner Endocardium—endothelial layer
Pericardium----fibrous and serous membrane
Pericardial fluid----25 to 35 ml
Myocardium----- three types of muscle fibers
i. Pacemaker
ii. Conductive system
iii. Contractile

8.
Serous membrane
Continuous with
blood vessels

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
4. Bathmotropic action.......Excitability of muscles

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

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.

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.
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.
Tricuspid Valve

15.
• The “ lub” is the first heart sound, commonly
termed S1, and is caused by turbulence
caused by the closure of mitral and tricuspid
valves at the start of systole. The second
sound,” dub” or S2, is caused by the closure of
aortic and pulmonic valves, marking the end
of systole.

16.
Chambers of the heart; valves

17.
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.

18.
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.

19.
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)

20.
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.

21.
Conduction System

22.
Heart Conduction System

23.
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.

24.
Cardiac Cycle cont…
• Atrial systole contributes 60 ml of blood to the
volume of 40 ml already in each ventricle.
• At the end of ventricular diastole, each ventricle
has 100 ml.
• This blood volume (100 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.

25.
❖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 60 ml of blood
each into the pulmonary trunk and aorta respectively.
• The blood volume remaining in each ventricle at the
end of systole, about 40 ml, is the end-systolic volume
(ESV).
• Stroke volume (the volume ejected per beat by each
ventricle) equals EDV minus ESV (SV=EDV—ESV ).

26.
• 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

27.
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

28.
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

29.
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

30.
Coronary Arteries (Anterior view)

31.
Coronary Arteries (posterior view)

32.
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)
35

33.
36
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”

34.
37
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

35.
38
• 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

36.
39
• Adventitia (t. externa) – longitudinally running
collagen and elastin for strength and recoil

37.
40
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

38.
41
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

39.
42
Exercise helps
circulation
(because
muscles
contract and
squeeze blood
back to the
heart)

40.
43
Vascular System
(Blood vessels of the body)
• Two circulations
– Systemic
– Pulmonary
• Arteries and veins usually run together
• Often nerves run with them

41.
44
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

42.
45
Pulmonary Circulation
• After gas exchange blood enters venules
• Larger and larger into Superior and Inferior Pulmonary
veins
• Four Pulmonary Veins empty into left atrium

43.
47
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.

44.
48
• 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