The cardiovascular system includes the heart and blood vessels. The heart pumps blood into vessels that circulate it throughout the body to supply nutrients and oxygen and remove waste. The heart has four chambers - the right and left atria receive blood, and the right and left ventricles pump it out. Valves ensure blood flows in only one direction. The conduction system initiates and coordinates heart contractions. Cardiovascular disorders disrupt blood flow and heart function, while vessel disorders involve blockages or damage.

1. CARDIOVASCULAR SYSTEM
Cardiovascular system includes heart and blood vessels. Heart pumps blood into the blood
vessels. Blood vessels circulate the blood throughout the body. Blood transports nutrients and
oxygen to the tissues and removes carbon dioxide and waste products from the tissues.
HEART
 Heart is a muscular organ that pumps blood throughout the circulatory system. It is
situated in between two lungs in the mediastinum.
 Right side of the heart has two chambers, right atrium and right ventricle. Right atrium is a
thin walled and low pressure chamber.
Right atrium receives venous (deoxygenated) blood via two large veins:
1. Superior vena cava that returns venous blood from the head, neck and upper limbs
2. Inferior vena cava that returns venous blood from lower parts of the body
 Left side of the heart has two chambers, left atrium and left ventricle. Left atrium is a thin
walled and low pressure chamber. It receives oxygenated blood from the lungs through
pulmonary veins. This is the only exception in the body, where an artery carries venous
blood and vein carries the arterial blood.
LAYERS OF WALL OF THE HEART
Heart is made up of three layers of tissues:
1. Outer pericardium
2. Middle myocardium
3. Inner endocardium.
PERICARDIUM
Pericardium is the outer covering of the heart. It is made up of two layers:
i. Outer parietal pericardium - Parietal pericardium forms a strong protective sac for the
heart. It helps also to anchor the heart within the mediastinum.
ii. Inner visceral pericardium - Inner visceral pericardium lines the surface of
myocardium. It is made up of flattened epithelial cells. This layer is also known as
epicardium.
The space between the two layers is called pericardial cavity or pericardial space and it contains a
thin film of fluid.
MYOCARDIUM

2. Myocardium is the middle layer of wall of the heart and it is formed by cardiac muscle fibers or
cardiac myocytes. Myocardium forms the bulk of the heart and it is responsible for pumping action
of the heart. Unlike skeletal muscle fibers, the cardiac muscle fibers are involuntary in nature.
ENDOCARDIUM
Endocardium is the inner most layer of heart wall. It is a thin, smooth and glistening membrane. It
is formed by a single layer of endothelial cells, lining the inner surface of the heart. Endocardium
continues as endothelium of the blood vessels.
VALVES OF THE HEART
Two valves are in between atria and the ventricles called atrioventricular valves. Other two are the
semilunar valves, placed at the opening of blood vessels arising from ventricles, namely systemic
aorta and pulmonary artery. Valves of the heart permit the flow of blood through heart in only one
direction.
Atrioventricular Valves

3. Left atrioventricular valve is otherwise known as bicuspid valve. It is formed by two valvular
cusps. Right atrioventricular valve is known as tricuspid valve and it is formed by three cusps.
Cusps of the valves are attached to papillary muscles by means of chordate tendineae. Papillary
muscles play an important role in closure of the cusps and in preventing the back flow of blood
from ventricle to atria during ventricular contraction.
Semilunar Valves
Semilunar valves are present at the openings of systemic aorta and pulmonary artery and are
known as aortic valve and pulmonary valve respectively. Because of the half moon shape, these
two valves are called semilunar valves. Semilunar valves are made up of three flaps. Semilular
valves open only towards the aorta and pulmonary artery and prevent the backflow of blood into
the ventricles.
THREE MAIN TYPES OF BLOOD VESSELS:
 Arteries. They begin with the aorta, the large artery leaving the heart. Arteries carry
oxygen-rich blood away from the heart to all of the body's tissues. They branch several
times, becoming smaller and smaller as they carry blood farther from the heart.
 Capillaries. These are small, thin blood vessels that connect the arteries and the veins. Their
thin walls allow oxygen, nutrients, carbon dioxide, and other waste products to pass to and
from our organ's cells.
 Veins. These are blood vessels that take blood back to the heart; this blood lacks oxygen
(oxygen-poor) and is rich in waste products that are to be excreted or removed from the
body. Veins become larger and larger as they get closer to the heart. The superior vena cava
is the large vein that brings blood from the head and arms to the heart, and the inferior vena
cava brings blood from the abdomen and legs into the heart.
BLOOD SUPPLY TO THE HEART
the right ventricle pumps the oxygen-poor blood to the lungs through the pulmonary valve. The
left atrium receives oxygen-rich blood from the lungs and pumps it to the left
ventricle through the mitral valve. The left ventricle pumps the oxygen-rich blood through the
aortic valve out to the rest of the body.
BRANCH OF AORTA
 descending aorta: The region of the aorta that passes inferiorly towards the feet. it runs
from the heart down the length of the chest and abdomen. It is divided into two portions,
the thoracic and abdominal, in correspondence with the two great cavities of the trunk in
which it sits. Within the abdomen, the descending aorta branches into the two common
iliac arteries that provide blood to the pelvis and, eventually, the legs.
 ascending aorta: The region of the aorta directly attached to the heart that passes
superiorly towards the head. The ascending aorta has two small branches, the left and

4. right coronary arteries. These arteries provide blood to the heart muscle, and their
blockage is the cause myocardial infarctions or heart attacks.
 arch of the aorta: The region of the aorta that changes direction between the ascending
and descending aorta. the brachiocephalic artery, which itself divides into right common
carotid artery and the right subclavian artery, the left common carotid artery, and the left
subclavian artery. These arteries provide blood to both arms and the head.
1. abdominal aorta: The largest artery in the abdominal cavity. As part of the aorta,
it is a direct continuation of the descending aorta (of the thorax).
2. thoracic Aorta: Contained in the posterior mediastinal cavity, it begins at the
lower border of the fourth thoracic vertebra where it is continuous with the aortic
arch, and ends in front of the lower border of the twelfth thoracic vertebra, at the
aortic hiatus in the diaphragm where it becomes the abdominal aorta.
3. internal iliac arteries: Formed when the common iliac artery divides the internal
iliac artery at the vertebral level L5 descends inferiorly into the lesser pelvis.
CARDIAC CONDUCTION SYSTEM
the cardiac conduction system is a collection of nodes and specialised conduction cells that
initiate and co-ordinate contraction of the heart muscle. It consists of:
 Sinoatrial node
 Atrioventricular node
 Atrioventricular bundle (bundle of His)
 Purkinje fibres
Sinoatrial Node

5.  The sinoatrial (SA) node is a collection of specialised cells (pacemaker cells), and is
located in the upper wall of the right atrium, at the junction where the superior vena cava
enters.
 These pacemaker cells can spontaneously generate electrical impulses. The wave of
excitation created by the SA node spreads via gap junctions across both atria, resulting
in atrial contraction (atrial systole) – with blood moving from the atria into the ventricles.
Atrioventricular Node
 After the electrical impulses spread across the atria, they converge at
the atrioventricular node – located within the atrioventricular septum, near the opening
of the coronary sinus.
 The AV node acts to delay the impulses by approximately 120ms, to ensure the atria have
enough time to fully eject blood into the ventricles before ventricular systole.
 The wave of excitation then passes from the atrioventricular node into the atrioventricular
bundle.
Atrioventricular Bundle
 The atrioventricular bundle (bundle of His) is a continuation of the specialised tissue of
the AV node, and serves to transmit the electrical impulse from the AV node to the
Purkinje fibres of the ventricles.
 It descends down the membranous part of the interventricular septum, before dividing
into two main bundles:
 Right bundle branch – conducts the impulse to the Purkinje fibres of the right ventricle
 Left bundle branch – conducts the impulse to the Purkinje fibres of the left ventricle
Purkinje Fibres
 The Purkinje fibres (sub-endocardial plexus of conduction cells) are a network of
specialised cells. They are abundant with glycogen and have extensive gap junctions.
 This rapid conduction allows coordinated ventricular contraction (ventricular systole)
and blood is moved from the right and left ventricles to the pulmonary artery and aorta
respectively.

6. cardiac cycle
EVENTS OF CARDIAC CYCLE
Events of cardiac cycle are classified into two:
1. Atrial events
2. Ventricular events.
atrial events
o atrial systole = 0.11 (0.1) sec
o atrial diastole = 0.69 (0.7) sec.
ventricular events
o ventricular systole = 0.27 (0.3) sec
o ventricular diastole = 0.53 (0.5) sec.
Atrial diastole Atria passively filling
Atrioventricular valves open
Atrial systole Action potential from the sinoatrial node (SAN)
Synchronous atrial contraction
Active filling of ventricles

7. Ventricular diastole Action potential from the sinoatrial node (SAN)
Synchronous atrial contraction
Active filling of ventricles
Ventricular systole Isovolumetric contraction – atrioventricular and semilunar valves are closed
Semilunar valve opens
Emptying of the ventricle
End-systolic volume
CARDIOVASCULAR DISORDERS
Angina pectoris - a condition marked by severe pain in the chest, often also spreading to the
shoulders, arms, and neck, owing to an inadequate blood supply to the heart.
myocardial infarction (MI) - commonly known as a heart attack, occurs when blood flow
decreases or stops to a part of the heart, causing damage to the heart muscle. The most common
symptom is chest pain or discomfort which may travel into the shoulder, arm, back, neck or jaw.
cardiac arrhythmia or heart arrhythmia – it is a group of conditions in which the heartbeat is
irregular, too fast, or too slow.The heart rate that is too fast – above 100 beats per minute in
adults – is called tachycardia, and a heart rate that is too slow – below 60 beats per minute – is
called bradycardia.

8. schemic heart disease- it is a condition of recurring chest pain or discomfort that occurs when a
part of the heart does not receive enough blood. This condition occurs most often during
exertion or excitement, when the heart requires greater blood flow.
DISORDER OF BLOOD VESSELS
Arteriosclerosis - occurs when the blood vessels that carry oxygen and nutrients from your heart
to the rest of your body (arteries) become thick and stiff, sometimes restricting blood flow to your
organs and tissues.
Atherosclerosis refers to the buildup of fats, cholesterol and other substances in and on your artery
walls (plaque), which can restrict blood flow.
Embolus - is often a small piece of a blood clot that impact in small vessel. The clot that travels
from the site where it formed to another location in the body.
Throbus - can lodge in a blood vessel and block the flow of blood in that location depriving
tissues of normal blood flow and oxygen.