Cardiovascular system

CARDIOVASCULAR SYSTEM
BY
SONI KUMARI SHAH

Cardiovascular System
The cardiovascular (cardio – heart, vascular – blood
vessels) system is divided for descriptive purposes into two
main parts:
The heart, whose pumping action ensures constant
circulation of the blood
The blood vessels, which form a lengthy network through
which the blood flows.

Organs Of Cardiovascular System
Blood: It is a fluid connective tissue.
Blood vessel: It is the channel in which blood is flowing.
Heart: It is a muscular blood pumping organ.

Blood Vessels
Blood vessels vary in structure,
size and function, and there are
several types:
Arteries
Arterioles
Capillaries
Venules
Veins
arterioles
venules

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 or outer layer of fibrous tissue
tunica media or middle layer of smooth muscle and elastic
tissue
tunica intima or inner lining of squamous epithelium called
endothelium.

The amount of muscular and elastic tissue
varies in the arteries depending upon their size
and function.
In the large arteries, including the aorta,
sometimes called elastic arteries, the tunica
media contains more elastic tissue and less
smooth muscle.
This allows the vessel wall to stretch,
absorbing the pressure wave generated by the
heart as it beats.

These proportions gradually change as the arteries branch many
times and become smaller until in the arterioles (the smallest
arteries) the tunica media consists almost entirely of smooth
muscle.
This enables their diameter to be precisely controlled, which
regulates the pressure within them.
Arteries have thicker walls than veins to withstand the high
pressure of arterial blood.

Anastomoses And End-arteries
Anastomoses are arteries that form a link between main
arteries supplying an area, e.g. the arterial supply to the palms of
the hand and soles of the feet, the brain, the joints and, to a
limited extent, the heart muscle.
If one artery supplying the area is occluded, anastomotic arteries
provide a collateral circulation.
This is most likely to provide an adequate blood supply when the
occlusion occurs gradually, giving the anastomotic arteries time
to dilate.

Anastomoses And End-arteries
An end-artery is an artery that is the sole source of blood to a
tissue, e.g. the branches from the circulus arteriosus (circle of
Willis) in the brain or the central artery to the retina of the eye.
When an end-artery is occluded the tissues it supplies die
because there is no alternative blood supply.

Capillaries And Sinusoids
The smallest arterioles break up into a number of minute vessels
called capillaries.
Capillary walls consist of a single layer of endothelial cells sitting
on a very thin basement membrane, through which water and
other small molecules can pass.
Blood cells and large molecules such as plasma proteins do not
normally pass through capillary walls.
The capillaries form a vast network of tiny vessels that link the
smallest arterioles to the smallest venules.

Capillaries And Sinusoids
In certain places, including the liver and bone marrow, the
capillaries are significantly wider and leakier than normal.
These capillaries are called sinusoids and because their walls
are incomplete and their lumen is much larger than usual, blood
flows through them more slowly under less pressure and can
come directly into contact with the cells outside the sinusoid wall.
This allows much faster exchange of substances between the
blood and the tissues.

Capillary Refill Time
When an area of skin is pressed firmly with a finger, it turns white
(blanches) because the blood in the capillaries under the finger
has been squeezed out.
Normally it should take less than two seconds for the capillaries to
refill once the finger is removed, and for the skin to turn pink
again.
Although the test may produce unreliable results, particularly in
adults, its use in children can be useful and a prolonged capillary
refill time suggests poor perfusion or dehydration.

Veins And Venules
Veins return blood at low pressure to the heart.
The walls of the veins are thinner than arteries but have the
same three layers of tissue .
They are thinner because there is less muscle and elastic
tissue in the tunica media, as veins carry blood at a lower
pressure than arteries.
When cut, the veins collapse while the thicker-walled
arteries remain open. When an artery is cut blood spurts at
high pressure while a slower, steady flow of blood escapes

Veins And Venules
Some veins possess valves, which prevent backflow of blood, ensuring that it
flows towards the heart.
They are formed by a fold of tunica intima and strengthened by connective
tissue.
The cusps are semilunar in shape with the concavity towards the heart.
Valves are abundant in the veins of the limbs.
They are absent in very small and very large veins in the thorax and abdomen.
Valves are assisted in maintaining one-way flow by skeletal muscles
surrounding the veins.

Veins And Venules
The smallest veins are called venules.
Veins are called capacitance vessels because they are
distensible, and therefore have the capacity to hold a large
proportion of the body’s blood.

Types Of Blood Vessels On The Basis Of Function
Conducting vessels
Distributing vessels
Resistance vessels
Exchanging vessels
Capacitance vessels

Blood Supply Of Blood Vessels
The outer layers of tissue of thick-walled blood vessels
receive their blood supply via a network of blood vessels
called the vasa vasorum.
Thin-walled vessels and the endothelium of the others
receive oxygen and nutrients by diffusion from the blood
passing through them.

Blood Vessel Diameter And Blood Flow
Resistance to flow of fluids along a tube is determined by three factors: the
diameter of the tube; the length of the tube; and the viscosity of the fluid.
The most important factor determining how easily the blood flows through
blood vessels is the diameter of the resistance vessels (the peripheral
resistance).
The length of the vessels and viscosity of blood also contribute to peripheral
resistance, but in health these are constant and are therefore not significant
determinants of changes in blood flow.
Peripheral resistance is a major factor in blood pressure regulation.
Constant adjustment of blood vessel diameter helps to regulate peripheral

Differences Between Artery And Vein
SN Arteries Vein
1 Arteries carry oxygenated blood,
away from heart except pulmonary
artery
Veins carry deoxygenated blood,
towards the heart except pulmonary
vein
2 These are mostly deeply situated in
the body.
These are superficial an deep in
location.
3 They have thick wall. They have thin wall.
4 They pass narrow lumen. They pass wide lumen.
5 They are reddish in color. They are bluish in color.
6 Arteries blood pressure is high. Veins blood pressure is low.
7 High elasticity. Low elasticity.
8 Internal valves are absent. Internal valves are present.

Thrombus and Embolus
A blood clot formed within the heart or blood vessels from the
constitute of blood, causing obstruction of blood vessel is known as
thrombus.
Embolus or embolism is a mass of undissolved matter present in the
blood vessel or lymphatic vessel causing obstruction, which is brought
there by blood or lymph and it may be solid, liquid or gaseous.

Heart
The heart is a roughly cone-
shaped hollow muscular organ.
It is about 10 cm long and is about
the size of the owner’s fist.
It weighs about 225 g in women
and is heavier in men (about 310
g).

Position of heart
The heart lies in the thoracic cavity in the
mediastinum (the space between the
lungs).
Vertebral level: 5th to 8th thoracic
vertebrae
It lies obliquely, a little more to the left
than the right, and presents a base
above, and an apex below.
The apex is about 9 cm to the left of the
midline at the level of the 5th intercostal
space, i.e. a little below the nipple and
slightly nearer the midline.

Apex Beat
The apex is the tip or summit of the heart and the apex beat is
the impact of the organ against the chest wall during systole.
The normal apex beat can be palpated in the pericardium on left
5th intercostal space.
In children apex beat occurs 4th intercostal space medial to
nipple.
Importance Of Apex Beat
Measurement of heart rate
Position of heart
Diagnosis of different heart diseases.

External Structure Of Heart
Surfaces of heart
Anterior surface
Inferior surface
Posterior surface
Right and left pulmonary surface
The coronary sulcus circles the heart, separating atria from the ventricle.
The anterior and posterior interventricular sulcus separates the two ventricles.

Organs associated with the
heart
Inferiorly – the apex rests on the central
tendon of the diaphragm
Superiorly – the great blood vessels, i.e.
the aorta, superior vena cava, pulmonary
artery and pulmonary veins
Posteriorly – the oesophagus, trachea,
left and right bronchus, descending aorta,
inferior vena cava and thoracic vertebrae
Laterally – the lungs – the left lung
overlaps the left side of the heart
Anteriorly – the sternum, ribs and

Structure Of Heart
The heart wall
The heart wall is composed of
three layers of tissue:
Pericardium
Myocardium and
Endocardium.

Pericardium
The pericardium is the outermost layer
and is made up of two sacs.
The outer sac (the fibrous pericardium)
consists of fibrous tissue and the inner
(the serous pericardium) of a
continuous double layer of serous
membrane.
The outer layer of the serous
pericardium, the parietal pericardium,
lines the fibrous pericardium. The inner
layer, the visceral pericardium, which is
continuous with the parietal pericardium,
is adherent to the heart muscle.

Pericardial Fluid
The serous membrane consists of flattened epithelial cells. It
secretes serous fluid, called pericardial fluid, into the space
between the visceral and parietal layers, which allows
smooth movement between them when the heart beats.

Myocardium
The myocardium is composed of
specialized cardiac muscle found only in
the heart.
It is striated, like skeletal muscle, but is
not under voluntary control.
Each fiber (cell) has a nucleus and one or
more branches.
The ends of the cells and their branches
are in very close contact with the ends
and branches of adjacent cells.
Microscopically these ‘joints’, or
intercalated discs, are thicker, darker lines
than the striations.
The myocardium is thickest at the apex
and thins out towards the base

Endocardium
This lines the chambers and valves of the heart.
It is a thin, smooth membrane to ensure smooth flow of
blood through the heart.
It consists of flattened epithelial cells, and it is continuous
with the endothelium lining the blood vessels.

Interior Of The Heart
Consists of
Chambers Of Heart(four)
Right Atrium
Right Ventricle
Left Atrium
Left Ventricle
Valves Of Heart
Atrioventricular Valve
Bicuspid Valve
Tricuspid Valve
Semi Lunar Valve
Pulmonary Valve
Aortic Valve

Chambers Of The Heart
Heart is made up of four chambers. Upper two chambers are known as
atrium and lower two chambers are known as ventricles.
Right Atrium
The right atrium serves as the receiving chamber for blood returning to the
heart from the systemic circulation.
The two major systemic veins, the superior and inferior venae cava, and the
large coronary vein called the coronary sinus that drains the heart
myocardium empty into the right atrium.
The superior vena cava drains blood from regions superior to the diaphragm:
the head, neck, upper limbs, and the thoracic region.
The inferior vena cava drains blood from areas inferior to the diaphragm: the
lower limbs and abdominopelvic region of the body.
The atria receive venous blood on a nearly continuous basis, preventing
venous flow from stopping while the ventricles are contracting. The opening
between the atrium and ventricle is guarded by the tricuspid valve.

Right Ventricle
The right ventricle receives blood from the right atrium through the
tricuspid valve.
Each flap of the valve is attached to strong strands of connective
tissue, the chordae tendineae, They connect each of the flaps to a
papillary muscle. There are three papillary muscles.
When the right ventricle contracts, it ejects blood into the pulmonary
trunk, which branches into the left and right pulmonary arteries that
carry it to each lung.
At the base of the pulmonary trunk is the pulmonary semilunar valve
that prevents backflow from the pulmonary trunk.

Left Atrium
After exchange of gases in the pulmonary capillaries, blood
returns to the left atrium high in oxygen via one of the four
pulmonary veins.
The opening between the left atrium and ventricle is
guarded by the mitral valve.

Left Ventricle
The muscular layer is much thicker in the left ventricle
compared to the right.
The mitral valve is connected to papillary muscles via chordae
tendineae.
There are two papillary muscles.
The left ventricle is the major pumping chamber for the
systemic circuit; it ejects blood into the aorta through the aortic
semilunar valve.

Valves Of Heart
Atrioventricular Valve:
Right atrioventricular valve: it lies between
right atrium and right ventricle. It is also
known as tricuspid valve. It has three flaps.
Left atrioventricular valve: it lies between left
atrium and left ventricle. It is also known as
bicuspid valve or mitral valve. It has two flaps.
Semilunar Valve: these are the two types of
valve found on the main branch of arteries
Pulmonary valve: it lies in the opening of
pulmonary trunk.
Aortic valve: it lies in the opening of aorta.

The heart is divided into a right and left side by the septum.
Each side is divided by an atrioventricular valve into the upper
atrium and the ventricle below.
The right atrioventricular valve (tricuspid valve) has three flaps
or cusps and the left atrioventricular valve (mitral valve) has two
cusps.
Flow of blood in the heart is one way; blood enters the heart via
the atria and passes into the ventricles below.

The valves between the atria and ventricles open and close
passively according to changes in pressure in the chambers.
They open when the pressure in the atria is greater than that in
the ventricles.
During ventricular systole (contraction) the pressure in the
ventricles rises above that in the atria and the valves snap shut,
preventing backward flow of blood prevented from opening
upwards into the atria by tendinous cords, called chordae
tendineae attached to papillary muscles.

Flow Of Blood Through The Heart
The two largest veins of the body, the
superior and inferior venae cava, empty
their contents into the right atrium.
 This blood passes via the right
atrioventricular valve into the right
ventricle, and from there is pumped into
the pulmonary artery or trunk (the only
artery in the body which carries
deoxygenated blood). The opening of the
pulmonary artery is guarded by the
pulmonary valve, formed by three
semilunar cusps. This valve prevents the
backflow of blood into the right ventricle
when the ventricular muscle relaxes.

Flow Of Blood Through The Heart
After leaving the heart the pulmonary artery
divides into left and right pulmonary
arteries, which carry the venous blood to the
lungs where exchange of gases takes place:
carbon dioxide is excreted and oxygen is
absorbed.
Two pulmonary veins from each lung carry
oxygenated blood back to the left atrium.
Blood then passes through the left
atrioventricular valve into the left ventricle,
and from there it is pumped into the aorta, the
first artery of the general circulation. The
opening of the aorta is guarded by the aortic
valve, formed by three semilunar cusps

Blood Supply To The Heart (The
Coronary Circulation)
Arterial Supply
The heart is supplied with arterial blood by the
right and left coronary arteries, which branch
from the aorta immediately distal to the aortic
Valve.
The coronary arteries receive about 5% of the
blood pumped from the heart, This large blood
supply, of which a large proportion goes to the
left ventricle, highlights the importance of the
heart to body function.
The coronary arteries traverse the heart,
eventually forming a vast network of capillaries.

Branches Of Right Coronary Artery
Anterior ventricular branch
Marginal branch
Posterior ventricular branch
Posterior interventricular artery
Atrial branch
Branches Of Left Coronary Artery
Anterior interventricular branch
Circumflex artery
Left marginal branch
Anterior ventricular and posterior ventricular branch
Atrial branches

Venous Drainage
Most of the venous blood is
collected into a number of cardiac
veins that join to form the
coronary sinus, which opens into
the right atrium.
The remainder passes directly into
the heart chambers through little
venous channels.

Tributaries Of Coronary Sinus
Great cardiac vein
Middle cardiac vein
Small cardiac vein
Left posterior ventricular vein
Left marginal vein
Anterior cardiac vein

Nerve Supply Of Heart
Sympathetic supply
From cardiac plexus formed from cervical and upper thoracic portion of sympathetic
trunk.
It increases the conductivity and contractility of heart muscles.
Sympathetic nerves supply the SA and AV nodes and the myocardium of atria
and ventricles, and stimulation increases the rate and force of the heartbeat.
Parasympathetic supply
From vagus nerve
It decreases conductivity and contractility.
Supplies SA and AV nodes and atrial muscle. Vagal stimulation reduces the
rate at which impulses are produced, decreasing the rate and force of the
heartbeat.

Conducting System Of The Heart
The heart possesses the property of auto rhythmicity, which means it
generates its own electrical impulses and beats independently of
nervous or hormonal control, i.e. it is not reliant on external mechanisms
to initiate each heartbeat.
Small group of specialized neuromuscular cells in the myocardium
initiate and conduct impulses causing a co-ordinate and synchronized
contraction of heart muscles.
Components Of Conducting System
1. SA (Sinoatrial) node
2. AV(Atrioventricular) node
3. Bundle of His or AV Bundle
4. Subendocardial plexus of purkinje fibers

Sinoatrial node (SA node)
This small mass of specialized cells lies in the wall of the right atrium
near the opening of the superior vena cava.
The sinoatrial cells generate these regular impulses because they are
electrically unstable.
This instability leads them to discharge (depolarize) regularly, usually
between 60 and 80 times a minute.
This depolarization is followed by recovery (repolarization), but almost
immediately their instability leads them to discharge again, setting the
heart rate.
Because the SA node discharges faster than any other part of the heart,
it normally sets the heart rate and is called the pacemaker of the
heart.
Firing of the SA node triggers atrial contraction.

Atrioventricular node (AV node)
This small mass of neuromuscular tissue is situated in the wall of the
atrial septum near the atrioventricular valves.
Normally, the AV node merely transmits the electrical signals 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 allows the atria to finish
contracting before the ventricles start.
The AV node also has a secondary pacemaker function and takes
over this role if there is a problem with the SA node itself, or with the
transmission of impulses from the atria.
Its intrinsic firing rate, however, is slower than that set by the SA node
(40–60 beats per minute).

Atrioventricular bundle (AV bundle or bundle of His) and
Purkinje Fibers
This mass of specialized fibers originates from the AV node.
The AV bundle crosses the fibrous ring that separates atria and ventricles
then, at the upper end of the ventricular septum, it divides into right and
left bundle branches.
Within the ventricular myocardium the branches break up into fine fibers,
called the Purkinje fibers.
The AV bundle, bundle branches and Purkinje fibers transmit electrical
impulses from the AV node to the apex of the myocardium where the
wave of ventricular contraction begins, then sweeps upwards and
outwards, pumping blood into the pulmonary artery and the aorta.

Mechanism Of Action Of Conducting System
The impulses from SA node are conducted to
AV node by three types of internodal fibers.
All these fibers converge towards the AV
node and interdigitate with fibers of AV
node, the bundle of His arises and this
divides into right and left branches.
These branches run on either side of
interventricular septum and gives off
Purkinje fibers which spread all over the
ventricular myocardium.

The Cardiac Cycle
At rest, the healthy adult heart is likely to beat at a rate of 60–80
beats per minute (bpm). During each heartbeat, or cardiac
cycle, the heart contracts (systole) and then relaxes (diastole).
The rhythmic contraction and relaxation of heart chambers in
cyclic pattern is called cardiac cycle.
During each heart beat or cardiac cycle the heart contract and
then relax.
The period of contraction is called systole and relaxing period is
called diastole.
The complete cardiac cycle is of 0.8 seconds.

Stages Of The Cardiac Cycle
Taking 74 bpm as an example,
each cycle lasts about 0.8 of a
second and consists of:
Atrial Systole –
contraction of the atria
Ventricular Systole –
contraction of the ventricles
Complete Cardiac
Diastole – relaxation of the atria
and ventricles.

Arterial Systole
Simultaneous contraction of both atria.
Opens AV valves( bicuspid and tricuspid valves).
Blood flows within the ventricles of respective sides.
No heart sound is produced.
Completes within 0.1 sec.

Ventricular Systole
Simultaneous contraction of both ventricles.
Bicuspid and Tricuspid valves get closed so that first heart sound
(LUBB) is produced
Blood is forced into pulmonary artery and aorta.
It completes within 0.3 seconds.

Complete Cardiac Diastole
Relaxation of both atria and ventricles together.
Both atria gets filled with blood.
Pulmonary and aortic valves get closed to prevent backflow of
blood so that second heart sound(DUBB) is produced.
It completes within 0.4 seconds.

Control Of Cardiac Cycle
Intrinsic Control
The heart beat originates and is controlled by SA node present
within the heart. SA node rhythmically generates the impulses
throughout the life.
Extrinsic Control
Though cardiac impulse is self generated and controlled, it can be
changed extrinsically(outside the heart) by hormones and neural
impulses.

Extrinsic Control
Hormonal Control
Various hormones like thyroxin, insulin, adrenaline, nor adrenaline and
sex hormones directly act on the SA node stimulating and inhibiting the
cardiac impulse.
Neural Impulse
The cardiovascular area is situated in the medulla. Heart is under control
of autonomic nervous system. ANS have two group of nerve fibers:
sympathetic and parasympathetic. Vagus nerve from parasympathetic
nervous system slows the heart rate while sympathetic nerves accelerate
the heart beat.

Heart Sound
There are four heart sounds, each corresponding to a particular event in
the cardiac cycle. The first two are most easily distinguished, and sound
through the stethoscope like ‘lub dup’.
The first sound (S1), ‘lub’, is fairly loud and is due to the closure of the
atrioventricular valves. This corresponds with the start of ventricular
systole.
The second sound(S2), ‘dup’, is softer and is due to the closure of the
aortic and pulmonary valves. This corresponds with ventricular diastole.
In both cases, as the valves close, the openings within the atrioventricular
septum guarded by the valves will become reduced, and blood flow
through the opening will become more turbulent until the valves are fully

Heart Sound
There is a third heart sound, S3, but it is rarely heard in healthy
individuals. It may be the sound of blood flowing into the atria, or
blood sloshing back and forth in the ventricle, or even tensing of
the chordae tendineae. S3 may be heard in youth, some athletes,
and pregnant women. If the sound is heard later in life, it may
indicate congestive heart failure, warranting further tests.
The fourth heart sound, S4, results from the contraction of the
atria pushing blood into a stiff or hypertrophic ventricle, indicating
failure of the left ventricle. S4 occurs prior to S1

Heart Murmur
The term murmur is used to describe an unusual sound coming from the
heart that is caused by the turbulent flow of blood.
Murmurs are graded on a scale of 1 to 6, with 1 being the most common,
the most difficult sound to detect, and the least serious. The most severe is
a 6.
Phonocardiograms or auscultograms can be used to record both
normal and abnormal sounds using specialized electronic stethoscopes.
During auscultation, it is common practice for the clinician to ask the
patient to breathe deeply. This procedure not only allows for listening to
airflow, but it may also amplify heart murmurs. Inhalation increases blood
flow into the right side of the heart and may increase the amplitude of
right-sided heart murmurs. Expiration partially restricts blood flow into
the left side of the heart and may amplify left-sided heart murmurs.

Proper Placement Of The Bell Of The Stethoscope To Facilitate
Auscultation.

Electrocardiogram (ECG)
The body tissues and fluids conduct electricity well, so
the electrical activity in the heart can be recorded on the
skin surface using electrodes positioned on the limbs
and/or the chest.
This recording, called an electrocardiogram (ECG)
shows the spread of the electrical signal generated by
the SA node as it travels through the atria, the AV node
and the ventricles.
The normal ECG tracing shows five waves which, by
convention, have been named P, Q, R, S and T.
The P wave arises when the impulse from the SA node
sweeps over 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).

The T wave represents the relaxation of the ventricular
muscle (ventricular repolarisation).
Atrial repolarisation occurs during ventricular
contraction, and so is not seen because of the larger
QRS complex.
The ECG described above originates from the SA node
and is called sinus rhythm. The rate of sinus rhythm is
60–100 b.p.m. A faster heart rate is called tachycardia
and a slower heart rate, bradycardia.
By examining the pattern of waves and the time interval
between cycles and parts of cycles, information about
the state of the myocardium and the cardiac conduction

Careful analysis of the ECG reveals a detailed picture of
both normal and abnormal heart function, and is an
indispensable clinical diagnostic tool.
The standard electrocardiograph (the instrument that
generates an ECG) uses 3, 5, or 12 leads.
The greater the number of leads an electrocardiograph
uses, the more information the ECG provides.
The term “lead” may be used to refer to the cable from
the electrode to the electrical recorder, but it typically
describes the voltage difference between two of the
electrodes.

The 12-lead electrocardiograph uses 10
electrodes placed in standard locations on
the patient’s skin.
In continuous ambulatory
electrocardiographs, the patient wears a
small, portable, battery-operated device
known as a Holter monitor, or simply a
Holter, that continuously monitors heart
electrical activity, typically for a period of 24
hours during the patient’s normal routine.

Uses of ECG
Determining and diagnosis of
Hear rate
Heart rhythm
Abnormal electrical condition
Poor blood flow to heart muscle
Heart attack
Coronary heart disease
Hypertrophy of heart

Blood Pressure
Blood pressure is the force or pressure that the blood exerts on the walls
of blood vessels.
Systemic arterial blood pressure maintains the essential flow of blood into
and out of the organs of the body.
Keeping blood pressure within normal limits is very important.
If it becomes too high, blood vessels can be damaged, causing clots or
bleeding from sites of blood vessel rupture.
If it falls too low, then blood flow through tissue beds may be inadequate.
This is particularly dangerous for essential organs such as the heart, brain
or kidneys.

Blood Pressure
The systemic arterial blood pressure, usually called simply arterial
blood pressure, is the result of the discharge of blood from the left
ventricle into the already full aorta.
Blood pressure varies according to the time of day, the posture,
gender and age of the individual.
Blood pressure falls at rest and during sleep.
It increases with age and is usually higher in women than in men.

Systolic And Diastolic Pressures
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.
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. In an adult this is about 80 mmHg.
The difference between systolic and diastolic blood pressures is the pulse
pressure.
Arterial blood pressure (BP) is measured with a sphygmomanometer and is
usually expressed with the systolic pressure written above the diastolic
pressure.

Types Of Blood Pressure
Systolic Blood Pressure
This is the maximum pressure exerted in the arteries during the systole of
heart. The normal systolic pressure is 120mm of Hg.
Diastolic Blood Pressure
This is the minimum pressure in the arteries during the diastole of heart.
The normal diastolic blood pressure is 80 mm of Hg.
Pulse Pressure
This is the differences between the systolic and diastolic pressure.
Normally it is 40 mm of Hg.

Factors Determining Blood Pressure
Blood pressure is determined by cardiac output and
peripheral resistance. Change in either of these parameters
tends to alter systemic blood pressure, although the body’s
compensatory mechanisms usually adjust for any significant
change.
Blood pressure = Cardiac output X Peripheral resistance

Factors Affecting Blood Pressure
Cardiac output
Peripheral resistance
Age
Sex
Posture is recumbent position
Exercise
Emotion and Excitement
Temperature
Blood volume

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 = Stroke volume X Heart rate.
In a healthy adult at rest, the stroke volume is approximately 70
mL and if the heart rate is 72 per minute, the cardiac output is 5
L/minute.
This can be greatly increased to meet the demands of exercise to
around 25 L/minute, and in athletes up to 35 L/minute. This
increase during exercise is called the cardiac reserve.

Stroke Volume
The stroke volume is determined by the volume of blood in
the ventricles immediately before they contract, i.e. the
ventricular end-diastolic volume (VEDV), sometimes
called preload. In turn, preload depends on the amount of
blood returning to the heart through the superior and
inferior venae cava (the venous return).

Factors Affecting Stroke Volume
VEDV (ventricular end-diastolic volume – preload)
Venous return
position of the body
skeletal muscle pump
respiratory pump
Strength of myocardial contraction
Blood volume

Heart Rate
Heart rate is the speed of the heart beat measured by the number of
contractions (beats) of the heart per minute (bpm).
The Main Factors Affecting Heart Rate
Gender
Autonomic activity
Age
Circulating hormones
Activity and exercise
Temperature
The baroreceptor reflex
Emotional states

Control Of Blood Pressure (BP)
Blood pressure is controlled in two ways:
short-term control, on a moment-to-moment basis, which mainly
involves the baroreceptor reflex, discussed below, and also
chemoreceptors and circulating hormones
long-term control, which involves regulation of blood volume by
the kidneys and the renin–angiotensin aldosterone system.

Short-term Blood Pressure Regulation
The cardiovascular center (CVC) is a collection of interconnected
neurons in the medulla and pons of the brain stem. The CVC
receives, integrates and coordinates inputs from:
baroreceptors (pressure receptors)
Chemoreceptors
higher centers in the brain.
The CVC sends autonomic nerves (both sympathetic and
parasympathetic) to the heart and blood vessels. It controls BP by
slowing down or speeding up the heart rate and by dilating or
constricting blood vessels. Activity in these fibers is essential for
control of blood pressure.

Long-term Blood Pressure Regulation
Slower, longer lasting changes in blood pressure are effected by
the renin–angiotensin–aldosterone system (RAAS) and the action
of antidiuretic hormone (ADH).
Both of these systems regulate blood volume, thus influencing
blood pressure.
In addition, atrial natriuretic peptide (ANP), a hormone released by
the heart itself, causes sodium and water loss from the kidney and
reduces blood pressure, opposing the activities of both ADH and
the RAAS.

Pulse
The pulse can be felt with gentle finger pressure in a superficial artery
when its wall is distended by blood pumped from the left ventricle during
contraction (systole).
The wave passes quickly as the arterial wall recoils.
Each contraction of the left ventricle forces about 60–80 mm of blood
through the already full aorta and into the arterial system.
The aortic pressure wave is transmitted through the arterial system and
can be felt at any point where a superficial artery can be pressed firmly
but gently against a bone.

Pulse
The number of pulse b.p.m. normally represents the heart rate and
varies considerably in different people and in the same person at
different times.
An average of 60–80 is common at rest. Information that may be
obtained from the pulse includes:
the rate at which the heart is beating
the regularity of the heartbeat
the artery wall should feel soft and pliant under the fingers.

Pulse Rate
In health, the pulse rate and the heart rate are identical.
In certain circumstances, the pulse may be less than the heart rate.
This may occur, for example, if:
The arteries supplying the peripheral tissues are narrowed or
blocked and the blood therefore is not pumped through them with each
heartbeat. Provided enough blood is reaching an extremity to nourish it, it
will remain pink in colour and warm to touch, even if the pulse cannot be
felt
There is some disorder of cardiac contraction, e.g. atrial fibrillation and
the heart is unable to generate enough force, with each contraction, to
circulate blood to the peripheral arteries.

Factors Affecting The Pulse Rate
Age
Gender
Body built
Exercise activity
Stress and emotions
Body temperature
Blood volume

Normal Pulse Rate According To Age
Infants 100-160
Preschoolers 80-110
School age 70-100
Adolescent 60-90
Adult 60-100

Measurement Of Pulse And Blood Pressure

Circulation Of Blood
The movement and distribution of blood in body in different organs
through blood vessels is called circulation.
Circulation in our body are mainly of four types:
Pulmonary Circulation
Systemic Or General Circulation
Portal Circulation
Coronary Circulation

Pulmonary Circulation
This is the circulation of blood from the right ventricle of the heart to the lungs and back
to the left atrium. In the lungs, carbon dioxide is excreted and oxygen is absorbed.
The pulmonary artery or trunk, carrying deoxygenated blood, leaves the upper part of
the right ventricle of the heart.
It passes upwards and divides into left and right pulmonary arteries which enters to
the left and right lungs respectively.
Within the lung these arteries divide and subdivide into smaller arteries, arterioles and
capillaries.

Pulmonary Circulation
The exchange of gases takes place between capillary blood and air in
the alveoli of the lungs.
In each lung the capillaries containing oxygenated blood merge into
progressively larger venules, and eventually form two pulmonary veins.
Two pulmonary veins leave each lung, returning oxygenated blood to the
left atrium of the heart.
In this way the deoxygenated blood is pumped from right ventricle and the
oxygenated blood comes to the left atrium of heart is called pulmonary
circulation.

Systemic Circulation
The systemic circulation involves all the blood vessels of the body that are
not part of the pulmonary circulation. The oxygenated blood is pumped
out from the heart through aorta and received through vena cava in right
atrium is called systemic circulation.
The blood pumped out from the left ventricle is carried by the
branches of the aorta around the body and returns to the right
atrium of the heart by the superior and inferior vena cava.

Systemic Circulation
The blood from left ventricle is pumped out through aorta. The
branches of arch of aorta supply to head, neck and upper limb. The
thoracic aorta supplies blood to lungs, esophagus and muscles of
thoracic region. The abdominal aorta supplies stomach, spleen, liver,
intestines, reproductive organs and lower limb.
The blood is drained by superior and inferior vena cava. The blood
from upper limb, head and neck is drained by superior vena cava to
right atrium. The venous blood from lower limb, abdominal and pelvic
organs is drained by inferior vena cava into right atrium. The venous
blood from thoracic area is drained by azygous and hemiazygous
vein to superior vena cava.

Portal Circulation
In portal circulation, venous blood passes from the capillaries bed of
abdominal part of digestive system, spleen and pancreas to the liver.
It passes through a second capillary bed, the hepatic sinusoids in the
liver before entering the general circulation via the inferior vena cava.
In this way blood with high concentration of nutrients, absorbed from
the stomach and intestine goes to the liver.

Coronary Circulation
The heart is supplied with blood by the right and left coronary arteries.
Right coronary artery gives marginal, posterior interventricular
branches. Left coronary artery is larger branch and gives anterior
interventricular, circumflex and diagonal branches.
Most of the blood is collected by several small veins ( great cardiac,
middle cardiac, small cardiac, anterior cardiac, marginal) that joins to
form the coronary sinus which opens into the right atrium.

Importance Of Circulation
To carry O2, nutrition, vitamins to the tissue.
To carry away different metabolic waste products and CO2 from tissues
for elimination.
To prevent intravascular coagulation of blood.
Helps to maintain thermal balance throughout the body.

Cardiovascular system

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