The cardiovascular system consists of the heart and blood vessels. The heart pumps blood through a network of arteries, capillaries and veins. The heart has four chambers and is composed of three layers. It is located in the chest cavity slightly left of center. The heart's natural pacemaker, the sinoatrial node, initiates electrical impulses that cause coordinated contractions. Blood pressure, cardiac output and peripheral resistance determine blood flow. Diseases can disrupt blood flow and oxygen delivery, like atherosclerosis, heart failure and ischemic heart disease including angina and myocardial infarction.

1. Cardiovascular system
Prepared by: Abhishek Dabra
Assistant Professor
Pharmacology
GGSCOP

2. Cardiovascular system
This system divided into two main
parts
• Cardio (Heart): whose pumping
actin ensure constant circulation
of blood
• Vascular (Blood vessels): which
form a lengthy network
throughout the body through
which blood flows.
Lymphatic system is closely
associated with cardiovascular
system both structurally and
functionally.

3. Structure of Heart
• The heart is cone shaped organ
which is about 10 cm long,
approximately the size of the
owners fist.
• It weigh varies from 225 g to
400 g.
• The heart lies in the thoracic
cavity between the lungs
(mediastinum cavity). It lies a
little more toward left side and
present a base above and an
apex below.
• The heart wall is composed of
three layers of tissues i.e.
pericardium, myocardium &
Endocardium

4. Pericardium
• It is the outermost layer made up of two sacs i.e. Fibrous
pericardium (outer layer) and serous pericardium (Inner layer).
The inelastic fibrous nature of this layer prevents overdistension
of the heart.
• Serous pericardium has two layers:
i. Parietal pericardium; attached with fibrous percardium
ii. Visceral pericardium; is adhered to heart muscle.
Serous pericardium consist of flattened epithelial cells, secretes
serous fluid called pericardial fluid (present between parietal an
visceral pericardium)

5. Myocardium
• It composed of specialized cardiac muscle found only in heart. It
is striated like skeletal muscle but an involuntary muscle.
• The end of the cell and their branches are very close contact with
the ends and branches of adjacent cells.
• Microscopically these joint or intercalated disc are thicker, darker
lines than the striations. Due to this arrangement cardiac muscle
appear as a sheet rather than a very large number of individual
cells.
• Because of end to end continuity of the fibers, each one does not
need to have a separate nerve supply.
• When an impulse is initiated it spreads from cell to cell via the
branches and intercalated discs over the whole ‘sheet’ of muscle,
causing contraction

6. Myocardium contd.
• The sheet arrangement of myocardium enables the atria and
ventricle to contact in a coordinated and efficient manner.
• Apex of myocardium is thick while base is thin comparatively.

7. Endocardium
• This lines the chamber and valve of the heart. It is thin smooth
membrane to ensure smooth flow of blood throughout the heart
• Consist of flattened epithelial cells and is continuous with the
endothelium lining the blood vessels.

8. Heart

10. Structure and function of Blood vessels
(artery, vein and capillaries)
• Blood vessels vary in structure, size and function and there are
several types: Arteries, arterioles, capillaries, venules and veins
Arteries and arterioles:
These blood vessels transport blood away from the heart. They
vary considerably in size and their walls consist of three layers of
tissue
• Tunica adventitia (Outer fibrous tissue layer)
• Tunica media (Middle layer of smooth muscle and elastic tissue)
• Tunica intima (Inner most layer of squamous epithelium known
as endothelium)

11. Capillaries and sinusoids
• The smallest arteries breakup into a number of minute
vessels called capillaries. Capillary wall consist of a single layer
of endothelial cells sitting on a very thin basement
membrane, through which water and other small molecule
can pass.
• Blood cells and large molecule (plasma proteins) do not
normally pass through capillary walls.
• The capillary form a vast network of tiny vessels that link the
smallest arterioles to the smallest venules.
• The capillary bed is the site of exchange of substance
between the blood and tissue fluid which bathes the body
cells and with the exception of those on the skin surface and
in the cornea of the eye, every body cells lies close to a
capillary.

12. Capillaries and sinusoids contd.
• Entry to capillary bed is guarded by smooth muscle (Capillary
sphincter) that direct blood flow.
• In certain places, including the liver and bone marrow, the
capillaries are significantly wider and leakier than normal and
are known as sinusoids.
• Due to their incomplete wall and larger lumen, blood flow
with less pressure and can come directly in contact with the
cells outside the sinusoid wall
• This allows much faster exchange of substances between the
blood and the tissues.

13. Veins and venules
• Veins returns blood at low pressure to heart. Walls of vein are
thinner than arteries but have the same three layers of tissue.
• They are thin because there is less muscle and elastic tissue in
the tunica media, as vein carry low blood pressure than arteries.
When cut, the veins collapse while the thicker walled arteries
remain open and blood spurts at high pressure while a steady
flow of blood escapes from a vein.
• Some veins possess valve ( valve cusp) which prevent back flow
of blood and ensure the flow of blood towards heart. Cusp are
semilunar in shape.

14. Anastomoses and End-arteries
• Anastomoses are the arteries that form a link between main
arteries supplying an area e.g. palms of hands, soles of feet, the
brain and joint, if any artery supplying the area is occluded
anastomotic arteries provide a co-lateral circulation just to provide
an adequate time to the main artery to dilate.
• An End-artery is an artery that is the sole source of blood to a tissue
e.g. branches from the circulus arterious in the brain and central
artery to the retina of eye. When an end-artery is occluded, the
tissue it supplies die because there is no alternative blood supply.

15. Element of conduction system of heart
• The heart possesses the property of auto-rhythmicity which
means it generate its own electrical impulse and beats
independently of nervous or hormonal control i.e. it is not reliant
on external mechanism to each heart beat.
• However it is supplied with both sympathetic and
parasympathetic nerve fibers which increase or decreases
respectively the intrinsic heart rate.
• In addition the heart respond to a number of circulating
hormones, including adrenaline and thyroxine.
• Small group of specialized neuromuscular cells in the
myocardium initiate and conduct impulses, causing coordinated
and synchronized contraction of heart muscle.

16. Sino-Atrial node (SA node)
• Small mass of specialized cells
lies in the wall of right atrium
near the opening of superior
vena cava.
• Sino-atrial cells generate
regular impulses because they
are electrically unstable. This
instability leads them to
discharge (depolarize) regularly
(usually 60 to 80 times a
minute).
• This depolarization is followed
by recovery (repolarization) but
almost immediately their
instability leads them to
discharge again.

17. Atrio-ventricular (AV) node
• This small mass of neuromuscular tissue is situated in the wall of
the atrial septum near atrio-ventricular valve.
• The AV node merely transmit the electrical signal from the atria
into the ventricles. There is a delay here; the electrical signal takes
0.1 of a second to pass through into the ventricles. This allow the
atria to finish contracting before the ventricle starts.
• It acts as secondary pacemaker
Bundle of His
• The mass of specialized fibers originates from the AV node

18. The Cardiac cycle
• Normal heart beat
60 to 80 b. p. m.
• During each heart
beat / cardiac
cycle, the heart
contract (Systole)
and then relaxes
(diastole).
Stages of cardiac cycle:
• Atrial systole:
Contraction of the
atria
• Ventricular systole:
Contraction of
ventricles
• Complete cardiac
diastole: Relaxation
of atria and
ventricles

19. Cardiac output
• The cardiac output is the amount of blood ejected from each
ventricle every minute. The amount expelled by each contraction of
each ventricle is the stroke volume.
• Cardiac output is expressed in liter per minute (L/min). And can be
calculated by multiplying the stroke volume by the heart rate
(measured in beats per minute).
Cardiac output = Stroke volume X Heart rate
• Normal stroke volume 72 ml and heart rate is 72, so accordingly the
cardiac output is 5 L/min

20. Regulation of blood pressure
• Blood pressure is the force or pressure that the blood exerts on the
walls of blood vessels. There are two type of blood pressure
• Systolic blood pressure: When the left ventricle contracts and
pushes blood into the aorta, the pressure produced within the
arterial system is called the systolic blood pressure. In adults it is
about 120 mmHg or 16kPa.
• Diastolic blood pressure: In complete cardiac diastole when the
heart is resting following the ejection of blood, the pressure within
the arteries is much lower and is called diastolic blood pressure.
BP = 120/80 mmHg or BP= 16/11 kPa

21. Factors determining blood pressure
• Cardiac output
• Peripheral or arteriolar resistance
• Auto-regulation
Control of blood pressure:
Blood pressure is controlled in two way:
• Short term control, on a moment to moment basis, which mainly
involves the baroreceptor reflex, chemoreceptor and circulating
hormone
• Long term control, involves regulation of blood volume by kidney
and the renin-angiotensin-aldosterone system

22. Short term blood pressure regulation
• Cardiovascular center is
collection of inter
connected neurons in the
medulla and pons of the
brain stem. The CVC
receive, integrate,
coordinates and input
from:
• Baroreceptor
• Chemoreceptor
• Higher center in brain
• The CVC send autonomic
nerve to the heart and
blood vessels

26. Electrical changes in the heart
• Body tissue and fluid conduct electricity well so electrical activity of the heart
can be recorded on the skin surface using electrode positioned on the limbs and
chest.
• This recording is called as electrocardiogram (ECG). It shows the spread of
electrical signal generated by the SA node as it travels through the atria, AV
node and the ventricles.
• Normal ECG tracing shows five wave which have been named P, Q, R, S and T.
• The P wave arises when the impulse from the SA node sweeps overs the atria
(atrial depolarization).
• The QRS complex represents the very rapid spread of the impulse from the AV
node through the AV bundle and the purkinje fibers and the electrical activity of
the ventricular muscle (ventricular depolarization).
• A delay between the completion of P wave and onset of QRS complex
represents the conduction of the impulse through the AV node which is much
slower the conduction elsewhere in the heart, and allow atrial contraction to
finish completely before ventricular contraction starts.
• The T wave represents the relaxation of the ventricular muscle (ventricular
repolarization). Atrial repolarization occurs during ventricular contraction is not
seen because of larger QRS complex.

28. Disorder of heart
1. Shock:
Shock occurs when the metabolic needs of cells are not being met
because of inadequate blood flow. In effect, there is a reduction in
circulating blood volume, in blood pressure and in cardiac output.
This causes tissue hypoxia, an inadequate supply of nutrients and
the accumulation of waste products.
i. Hypovolaemic shock: This occurs when the blood volume is
reduced by 15 to 25%. Reduced venous return and in turn cardiac
output may occur following:
i. Hypovolaemic
ii. Cardiogenic
iii. Septic
iv. Neurogenic
v. Anaphylactic

29. a) severe hemorrhage — whole blood is lost
b) extensive superficial burns — serum is lost and blood cells at the
site of the burn are destroyed
c) severe vomiting and diarrhoea — water and electrolytes are lost
ii. Cardiogenic shock:
This occurs in acute heart disease when the damaged heart muscle
cannot maintain an adequate cardiac output, e.g. in myocardial
infarction
iii. Septic shock:
This is caused by severe infections in which endotoxins are
released into the circulation from dead Gram-negative bacteria,
e.g. Enterobacteria, Pseudomonas.
They cause an apparent reduction in the blood volume because of
vasodilatation and pooling of blood in the large veins. This reduces
the venous return to the heart and the cardiac output

30. iv. Neurogenic shock (vasovagal attack, fainting):
The causes include sudden acute pain, severe emotional experience,
spinal anesthesia and spinal cord damage. Parasympathetic nerve
impulses reduce the heart rate, and in turn, the cardiac output.
The venous return may also be reduced by the pooling of blood in
dilated veins. These changes effectively reduce the blood supply to the
brain, causing fainting. The period of unconsciousness is usually of short
duration.
v. Anaphylactic shock:
In allergic reactions an antigen interacts with an antibody and a variety
of responses can occur. In severe cases, the chemicals released, e.g.
histamine, bradykinin, produce widespread vasodilatation and
constriction of bronchiolar smooth muscle (bronchospasm).
The vasodilatation profoundly reduces the venous return and cardiac
output resulting in tissue hypoxia. Bronchospasm reduces the amount of
air entering the lungs, increasing tissue hypoxia.

31. 2. Disease of blood vessels:
Patchy changes (atheromatous plaques) develop in the tunica
intima of large and medium-sized arteries. These consist of
accumulations of cholesterol and other lipid compounds, excess
smooth muscle and fat-filled monocytes (foam cells). The plaque is
covered with a fibrous cap. As plaques grow they spread along the
artery wall forming swellings that protrude into the lumen.
3. Arteriosclerosis:
This is a progressive degeneration of arterial walls, associated with
ageing and accompanied by hypertension.
i) Large and medium arteries
The tunica media is infiltrated with fibrous tissue and calcium. This
causes the vessels to lose their elasticity. The lumen dilates and
they become tortuous Loss of elasticity increases systolic blood
pressure.

32. ii) Small arteries and arterioles:
Hyaline thickening of the tunica media and tunica intima causes
narrowing of the lumen and they become tortuous. These arteries
are the main determinants of peripheral resistance (p. 80) and
narrowing of their lumens increases peripheral resistance and
blood pressure.
Ischaemia of tissues supplied by affected arteries may occur. In the
limbs, the resultant ischaemia predisposes to gangrene which is
particularly serious in people with diabetes mellitus.
3. Cardiac failure
The heart is described as failing when the cardiac output is unable
to maintain the circulation of sufficient blood to meet the needs of
the body. In mild cases, cardiac output is adequate at rest and
becomes inadequate only when increased cardiac output is
required, e.g. in exercise.

33. 4. Ischaemic Heart Disease:
 Ischaemic heart disease is due to the effects of atheroma,
causing narrowing or occlusion of one or more branches of the
coronary arteries.
 The narrowing is caused by atheromatous plaques. Occlusion
may be by plaques alone, or plaques complicated by
thrombosis.
 The overall effect depends on the size of the coronary artery
involved and whether it is narrowed or occluded. Narrowing of
an artery leads to angina pectoris, and occlusion to myocardial
infarction, i.e. an area of dead tissue.
a) Angina pectoris:
This is sometimes called angina of effort because increased cardiac
output required during extra physical effort causes severe
ischaemic pain in the chest.

34. The pain may also radiate to the arms, neck and jaw. Other factors
which may precipitate angina include:
• Cold weather
• exercising after a heavy meal
• strong emotions.
b) Myocardial infarction
 An infarct is an area of tissue that has died because of lack of
oxygenated blood. The myocardium is affected when a branch
of a coronary artery is occluded.
 The commonest cause is an atheromatous plaque complicated
by thrombosis.
 The extent of myocardial damage depends on the size of the
blood vessel and site of the infarct.
 The damage is permanent because cardiac muscle cannot
regenerate and the dead tissue is replaced with non-functional
fibrous tissue.

35.  Speedy restoration of blood flow through the blocked artery
using clot-dissolving (thrombolytic) drugs can greatly reduce the
extent of the permanent damage and improve prognosis, but
treatment must be started within a few hours of the infarction
occurring.
 The effects and complications are greatest when the left
ventricle is involved.