Circulatory system

St. Wilfred’s Institute of Pharmacy, Panvel.
DTE CODE: 3485
TOPIC : Cardiovascular System
Presented by : Mr.Vijay Ikale(Ass.Professor Pharmacology)

Who discovered the circulation of blood ?
William Harvey (1 April 1578 – 3 June 1657) was an
English physician who made influential contributions
in anatomy and physiology.
He was the first known physician to describe completely,
and in detail, the systemic circulation and properties of
blood being pumped to the brain and the rest of the body
by the heart(1628).

Cardiovascular System
The circulatory system, also called cardiovascular system, is a vital organ
system that delivers essential substances to all cells for basic functions to occur. It is a
network composed of the heart , bloods vessels and the blood itself, for transportation
of different substances.
The circulatory system is divided into two separate loops: The shorter pulmonary
circuit that exchanges blood between the heart and the lungs for oxygenation; and the
longer systemic circuit that distributes blood throughout all other systems and tissues
of the body. Both of these circuits begin and end in the heart.

Blood
● Study of blood is known as heamatology (Greek : Haeme –
Blood , Logos – To study )
● Blood is liquid connective tissue which transports all nutrients and
oxygen to every cell
● Features of blood : Bright red, slightly alkaline(pH – 7.4), salty,
viscous liquid heavier than water
● Amount of blood present in average size adult : 5 liters
● Contributes around 8 % of total body weight

Blood Composition
45%
55%
Blood cells Plasma

Plasma
•Straw coloured, slightly alkaline and viscous fluid.
•It contains 90-92 % water and 8-10% solutes, most of which are
proteins(Plasma proteins are serum albumin, serum globulin,
heparin, fibrinogen and prothrombin)
• Other solutes are :
•Nutrients : such as glucose, amino acids, fatty acids, glycerols,
nitrogenous waste such as urea, uric acid ammonia and creatinine
•Gases : Oxygen, Carbon dioxide and Nitrogen
•Regulatory substances : Enzymes and Hormones
•Inorganic substances : Bicarbonates,Chlorides,Phosphates,Sulfates of s
Sodium, Potassium, Calcium, Magnesium

Blood cells
WBC (Leucocytes) RBC (Erythrocytes) Thrombocyte (Platelet)
RBC (Erythrocytes)
Erythros : Red , Kytos – Cell )

RBCs are red, circular, biconcave, non-nucleated cells
Size : Diameter - 7 micrometer and thickness - 2.5 micrometer
Adult Male RBCs count : 5.1 – 5.8 million RBCs per cubic millimeter
Female RBCs count : 4.3 to 5.2 million RBCs per cubic millimeter
Average life span of RBCs is about : 120 days
Process of formation of RBCs is called as erythropoiesis
Location of formation : Foetus – Spleen and liver , Adults – Red bone marrow
Recycling of RBCS after 120 days - Liver and spleen
Increase in number of RBCs is called as Polycythemia
Decrease in number of RBCs is called as Erythrocytopenia
Cytoplasm of RBCs contain a respiratory pigment called as haemoglobin which
helps in transport of oxygen and carbon dioxide
Normal haemoglobin content in male : 13-18 gm/100 ml of blood
Normal haemoglobin content in female : 11.-18 gm/100 ml of blood
Less haemoglobin leads to anemia
RBC (Erythrocytes)

WBCs are colourless, nucleated cells, amoeboid and phagocytic cells
Size : Diameter – 8-15 micrometer
WBCs count – 5000 to 9000 per cubic millimeter of blood
Average life span of WBCs is about : 3-4 days
Process of formation of WBCs is called as Leucopoiesis
Location of formation : Spleen, liver, Red bone marrow, lymph nodes, tonsils and
thymus
Recycling of WBCs after 3-4 days- Liver, blood and lymph nodes
Increase in number of WBCs is called as Leucocytosis
Decrease in number of WBCs is called as Leucocytopenia
Pathological increase in WBC count leads to Leukemia also known
as Blood cancer
WBC (Leucocytes)

Granulocytes : WBCs which contains cytoplasmic granules(agglomerates of particles)
Neutrophils :
1. Stained with neutral dyes
2. 3-5 Lobed nucleus
3. Contribution : 54-62 %
of total WBCs
4. Function : Phagocytic in
action
Eosinophils:
1. Stained with acidic dyes
2. Bilobed nucleus
3. Contribution : 3 % of total
WBCs
4. Function :
They play role in
minimizing inflammation
Basophils:
1. Stained with basic dye
2. Twisted nucleus
3. Contribution : 0.5 % of total
WBCs
4. Function :
a. Helps in blood clotting
b. Involves in tissue repair
. .mechanism

Agranulocytes : WBCs without cytoplasmic granules
Lymphocytes :
1. Large round nucleus
2. Contribution : 25-33 % of total WBCs
3. Function : Production of antibodies
and Immune response
Monocytes:
1. Kidney shaped nucleus
2. Contribution : 3-9 % of total WBCs
3. Function : Phagocytic in nature ;
Engulf and kills microorganisms

Platelets or Thrombocytes
1. Non nucleated, round and biconvex cells.
2. Size : 2.5 to 5 micrometer in diameter
3. Platelet count : 2.5 – 4.5 lakhs per cubic milliliter
4. Process of formation of Platelets is called as Thrombopoiesis
5. Location of formation : Red bone marrow
6. Increase in number of Thrombocytes is called as Thrombocytosis
7. Decrease in number of Thrombocytes is called as Thrombocytopenia
8. Function : Blood Clotting

Blood coagulation :
Inside an intact blood vessel, blood does not coagulate or clot due to presence of a chemical
known as heparin which acts as anticoagulant.
As soon as a blood vessel ruptures, bleeding starts. The conversion of liquid blood into
semisolid jelly is called as blood coagulation or clotting
Release of
Thromboplastin
Synthesis of enzyme Prothrombinase
Prothrombin(Inactive)
Thrombin(Active)
Fibrinogen (Soluble|) Fibrin (Insoluble)
Fibrin enmesh platelets, blood cells and plasma
Blood clotting
Ca++
Prothrombinase
Clotting Time : 2-8
min.

Anatomy of heart
• Heart is hollow muscular conical organ about size of one’s fist with broad base and
. narrow apex tilted towards left.
• Location : Almost in the middle of thoracic cavity in a space called as mediastinum
• Size : 12cm in length and 9 cm in breadth
• Weight of 250-300gm
12 cm
9 cm

Anatomy of heart
Protective Layers of
Heart
Internal structures
External structures
1. Pericardium
2. Heart Wall

Protective Layers of Heart : Pericardium
Heart is enclosed in doubled layered
membrane called as pericardium.
Layer 1 : Fibrous pericardium
It is outermost layer made up of tough
inelastic fibrous connective tissue
Layer 2 : Serous pericardium
It is inner layer made up of 2 sub layers :
a. Parietal layer
b. Visceral layer
Between these 2 layers pericardial fluid is
present; minimizes friction between layers
Function :
1.It prevent overextension and overloading
of heart
2. Also shields the heart by reducing
external friction

Protective Layers of Heart : Heart Wall

Protective Layers of Heart : Heart Wall
Wall of heart made up of 3 layers namely ; outer Epicardium, middle
Myocardium and inner Endocardium
1.Epicardium : Consist of single layer of flat epithelial cells .
The epicardium functions to protect the inner heart layers and also assists in the
production of pericardial fluid. This fluid fills the pericardial cavity and helps to
reduce friction between pericardial membranes. Also found in this heart layer are
the coronary blood vessels, which supply the heart wall with blood.
2.Myocardium : Composed of cardiac muscle fibers responsible for contraction
and relaxation of heart. The myocardium is the thickest layer of the heart wall,
with its thickness varying in different parts of the heart. The myocardium of the
left ventricle is the thickest, as this ventricle is responsible for generating the
power needed to pump oxygenated blood from the heart to the rest of the body.
3.Endocardium : Consist of single layer of flat epithelial cells. This layer lines
the inner heart chambers, covers heart valves, and is continuous with the
endothelium of large blood vessels

External structure of heart
1. Heart is made up of 4 chambers : Two superior, small, thin walled receiving
chambers called as atria and two inferior, large, thick walled, distributing chambers
called as ventricles.
2. Externally wall of heart situated with grooves in which coronary artery and veins are
located .
a. Coronary artery supplies oxygenated blood to heart
b. Coronary vein collects deoxygenated blood from heart
3. From right ventricle pulmonary artery arises and from left ventricle systemic artery
arises

● Venae cavae : In humans there are the superior vena cava and
the inferior vena cava, and both empty into the right atrium.
● Superior vena cava : The superior vena cava is the large vein
which returns deoxygenated blood to the heart from the head, neck
and both upper limbs
● Inferior vena cava : The inferior vena cava returns deoxygenated
blood to the heart from the lower limbs and middle body
(Abdomen)
External structure of heart

Superior vena cava
Inferior vena cava

● Opening of inferior vena cava is guarded by Eustachian valve
and opening of coronary sinus is guarded by Thebesian valve.
● What are valves ?
● Valves are flap-like structures present in heart that allow blood
to flow in one direction.

Internal structure of heart
Internally heart is made up of 4 chambers with 2 atria and 2
ventricles
Atria : Two thin walled receiving chambers placed superiorly and
separated from each other by interatrial septum
The right atrium receives deoxygenated blood from all over the body
through superior vena cava, inferior vena cava and coronary sinus

● Left atrium receives oxygenated blood from the lungs through 4
openings of pulmonary veins
RA : Deoxygenated
blood
LA: Oxygenated blood

Distribution of blood from atria to ventricle
● Each atrium opens into ventricles of its side through
atrioventricular aperture guarded by valves made up of
connective tissue.
● Right atrioventricular valve has 3 flaps hence called as
tricuspid valve and left atrioventricular valve has 2 flaps hence
called as bicuspid valve

Ventricles
● The ventricles are 2 thick walled distributing chambers placed
inferiorly and separated from each other by interventricular
septum
● Left ventricle has thickest wall as it has to pump blood to all
parts of body.
● From right ventricle pulmonary artery arises and from left
ventricle systemic artery arises

Pulmonary artery carry deoxygenated blood to lungs for oxygenation.
Systemic artery carry oxygenated blood to all parts of body.
Pulmonary and systemic artery has 3 semilunar valves at the base
which prevents backward flow of blood.

Pumping action of heart
● Heart act as a pumping organ.
● This pumping action is due to rhythmic contraction and
relaxation of myocardium
● The rhythmic contraction and relaxation of heart is known as
heart beat.
● Heart beats 72 times per minute ; also known as heart rate and
pumps 5 liter of blood per minute

Conduction system of heart
● Human heart is myogenic ( Made up of muscles )
● It contains modified cardiac muscle called as sinoatrial node (SA
node) which is present in wall of right atriam near the opening of
superior vena cava.
● SA node is also known as “Pace maker” because it has power of
generation of wave of contraction.
● This wave of contraction is conducted by cardiac muscle fiber to both
atria causing their contraction ( Atrial systole)

● AV node : Atrioventricular node is located in the wall of right atriam
near the opening of coronary sinus.
● AV node receives wave of contraction generated by SA node through
internodal pathway
Conduction system of heart

● Definition : Specialized heart muscle cells that transmit electrical
impulses from the AV node in the heart to the muscle cells of the
heart wall
● It arises from AV node and divides into 2 branches i.e right and left
bundle branches located in interventricular septum.
● The bundle branches give rise to purkinje fibers which penetrate into
myocardium of ventricles.
● The bundle of His and purkinje fibers conduct the wave of
contraction from AV node to myocardium of ventricles causing their
contraction.
Bundle of His

Working of Heart ( Cardiac Cycle )
● The events associated with one cardiac heart
beat is known as cardiac cycle
● It lasts for 0.8 seconds.
● Each heart beat includes :
1) Atrial systole
2) Ventricular systole
3) Joint diastole
● Atrial Systole : 0.1 Second.
During Atrial systole, the deoxygenated blood
from the right atrium enters the right ventricle
through atrioventricular aperture, the back
flow prevented by tricuspid valve AND
oxygenated blood from left atrium enters left
ventricle through atrioventricular aperture ,
the backflow is prevented by bicuspid valve

● Ventricular Systole : 0.3 Seconds.
During Ventricular systole, the deoxygenated
blood from the right Ventricle enters the
pulmonary artery, which carry blood to lungs
for oxygenation .
Oxygenated blood from left Ventricle enters
systemic artery which is supplied all over the
body, the backflow is prevented by
semilunar valve .

● Joint diastole : 0.4 seconds
During joint diastole both atria and ventricles
undergo relaxation
The right atrium receives deoxygenated blood
from all over the body through superior vena
cava, inferior vena cava and coronary sinus.
The left atrium receives oxygenated blood
from the lungs through two pairs of
pulmonary veins.

Regulation of cardiac activity
● Normal activities of heart are regulated by specialized muscles i.e.
cardiac muscle
● Its activity is auto regulated
● Then why heart rate increases or decreases ?
● Who controls heart rate ?

Nervous control of heart
The ANS is responsible for controlling many
physiological functions: inducing the force of contraction
of the heart, peripheral resistance of blood vessels and
the heart rate. The ANS has both sympathetic and
parasympathetic divisions that work together to maintain
balance.
The parasympathetic nervous system sends input into the
heart is via the vagus nerve (X). The vagus nerve forms
synapses with postganglionic cells in SA node and AV
node. When stimulated, acetylcholine which binds on to
M₂ receptors, which acts to decrease the heart rate
The sympathetic sends input into the heart is via the
postganglionic fibres from the sympathetic trunk which
innervate the SA node and AV node. The post ganglionic
fibres release noradrenaline, which acts on B₁
adrenoreceptors to increase heart rate as well as
increasing the force of contraction

Blood Vessels
The study of blood vessels is called as angiology.
Blood vessels are of three types : Arteries, Veins, Capillaries

Blood Vessels
Arteries :
Arteries carry blood away from the heart to different parts of body.
They carry oxygenated blood except pulmonary artery

Arteries :
They are thick walled, muscular, elastic and without valves inside
They are deeply situated in body, having narrow lumen and showing
high blood pressure for efficient circulation of blood. Histologically the
wall of artery is made up of three layers namely Outer tunica externa,
middle tunica media and inner tunica interna

Arteries divide and redivide into arterioles which further divide into
capillaries.

Capillaries : Capillaries are the thinnest blood vessels and formed by
division and redivision of arterioles.
1. Wall of capillary is made up of squamous epithelium.
2. It is permeable to water and dissolved substances.
3. Thus exchange of respiratory gases, nutrients, excretory products between blood
and tissue takes place through wall of capillaries.
4. These capillaries unite to form venules.

Veins : Venules unite to form vein
1. Veins carry deoxygenated blood from different parts of body to the heart
2. Exception : Pulmonary Vein ; carries oxygenated blood to left atrium
3. They are thin walled with semilunar valves to prevent backflow of blood
4. They are superficially situated, having broad lumen and showing low blood
pressure

Why do arteries lacks valves ?
Why are veins provided with valves ?
● Blood primarily moves in the veins by the rhythmic movement
of smooth muscle in the vessel wall and by the action of the
skeletal muscle as the body moves. Because most veins must
move blood against the pull of gravity, blood is prevented
from flowing backward in the veins by one-way valves.

Blood Pressure
Blood Pressure : Pressure exerted by circulating blood on wall of arteries
Normal Blood Pressure : 120/80 mmHg
1. Systolic : 120mmHg When Ventricles Contracts
2. Diastolic : 80 mmHg When Ventricles Relaxes
How blood pressure is
controlled?

Control of Blood Pressure
There are several mechanisms through which the body regulates arterial pressure :
1. Baroreceptor Reflex
In response to small (acute) changes in blood pressure, the body responds through the
baroreceptors located within blood vessels.
Baroreceptors are a form of mechanoreceptor that become activated by the stretching of the
vessel. This sensory information is transferred to the central nervous system(Brain and Spinal
Cord) and used to influence peripheral vascular resistance and cardiac output.

There are two forms of baroreceptors.
 High-Pressure Baroreceptors
Two baroreceptors are located within the high-pressure arterial
system.
1. The carotid baroreceptor responds to both increases and
decreases in blood pressure
2. The aortic arch baroreceptor responds only to increases in
blood pressure.
These both send signals in response to the physical distortion
of the vessel. The stretch of the vessel leads to an increase in
action potential relayed from the sensory endings located in the
tunica interna of the artery. These action potentials get
transmitted to the autonomic neurons. They secrete
neurotransmitters to affect the cardiovascular system.

● Activation of the aortic baroreceptor increases during high blood pressure and it
effectively inhibits the sympathetic nerve response.
● On the other hand, if an individual’s blood pressure were to fall such as in
hypovolemic shock, the rate of action potential from the baroreceptor would be
decreased due to reduced depolarization; this would lead to reduced inhibition of
sympathetic activity, resulting in a reflex to increase pressure.
● Low-Pressure Baroreceptors
● These baroreceptors are present within the low-pressure venous system. They exist
within large veins, pulmonary vessels, and within the walls of the right atrium and
ventricle. Changes in volume largely influence the baroreceptors in the venous
system. Decreased frequency in stimulation in low-pressure scenarios leads to the
secretion of antidiuretic hormone, renin, and aldosterone. These lead to a downstream
effect to regulate arterial pressure.

Antidiuretic Hormone
● Antidiuretic Hormone
● Antidiuretic hormone (ADH), also known as vasopressin.
● ADH is synthesized and released in response to multiple triggers which are:
● Low blood volume causes a decreased stretch in the low-pressure baroreceptors,
leading to the production of ADH
● Decreased blood pressure causes decreased stretch in the high-pressure baroreceptors,
also leading to the production of ADH
● Angiotensin II
● The antidiuretic hormone produced in the hypothalamus makes its way down the
pituitary stalk to the posterior pituitary where it is kept in reserve for release in
response to the above-listed triggers.
● ADH mainly functions to increase free water reabsorption in the collecting duct of the
nephrons within the kidney, causing an increase in plasma volume and arterial
pressure. ADH in high concentrations has also been shown to cause moderate
vasoconstriction, increasing peripheral resistance, and arterial pressure.

Renin-Angiotensin-Aldosterone
System (RAAS)
● The renin-angiotensin-aldosterone system is an essential regulator of arterial blood
pressure.
● The system relies on several hormones that act to increase blood volume and
peripheral resistance.
● It begins with the production and release of renin from juxtaglomerular cells of the
kidney.
● They respond to decreased blood pressure, sympathetic nervous system activity, and
reduced sodium levels within the distal convoluted tubules of the nephrons.
● In response to these triggers, renin is released from the juxtaglomerular cells and
enters the blood where it comes in contact with angiotensinogen which is produced
continuously by the liver.
● The angiotensinogen is converted into angiotensin I by renin. The angiotensin I then
make its way to the pulmonary vessels, where the endothelium produces the
angiotensin-converting enzyme (ACE).
● Angiotensin I is then converted to angiotensin II by ACE.

● Angiotensin II has many functions to increase arterial pressure, including:
1. Potent vasoconstriction of arterioles throughout the body
1. Increased sodium reabsorption within the kidney tubules - the increased sodium
reabsorption from the kidney tubules results in passive reabsorption of water through
osmosis; this causes an increase in blood volume and arterial pressure
2. It stimulates : The release of antidiuretic hormone (ADH) release from the posterior
pituitary gland and the release of aldosterone from the zona glomerulosa of the adrenal
cortex within the adrenal gland

ECG
● Electrocardiogram :
( Graphical representation of electrical activity of Heart )
Record of change in electrical potential in the heart due to
passage of cardiac impulse during the cardiac cycle and
recorded from surface of body

ECG
● Electrocardiograph :
Machine used to record electrical activity of Heart

History of ECG
The electrical activity of the heart was first recorded by Waller
in 1887 with a capillary electrometer but it was the work of
Einthoven (1901) that’s why he was awarded with Nobel prize
in 1924.

Parts of ECG
● ECG shows five waves designated from left to right with letters
P,Q,R,S and T
● P, R and T are normally upward or Positive waves
● Q and S are downward or Negative waves

● P Wave : Also known as Atrial Wave or Auricular complex
● P wave is due to spread of depolarization in the atria
● Its duration is 0.1 sec. and just precedes the Atrial systole.

QRS Complex
● Q wave : Small negative downward wave
● R wave : Prominent positive wave produced due to large size of ventricle
● S wave : Small Negative wave
● Q wave represents Septal depolarization which takes place when impulse
travels from SA node to AV node
● Here R and S are due to depolarization of ventricular muscle
● Its duration is 0.08 sec.

T wave
● T wave is positive wave occurring due to ventricular
repolarization
● Its duration is 0.27 sec

Additional Waves
● PR Segment : Impulse moves from SA node to
AV node. During this phase no current flowing
through cardiac muscle.

Additional Waves
● ST Segment : During this phase no current
flowing through cardiac muscle.

Circulatory system

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