THIS CONTENT WILL BE BENEFICIAL FOR B.SC. NURSING STUDENTS.

1. HEART
(Its Structure, Function, Blood
supply and Conduction System)

2. HEART
The heart is a roughly cone-shaped hollow muscular
organ found in all animals and human beings with a
circulatory system, that is responsible for pumping
blood throughout the blood vessels by repeated,
rhythmic contractions. The term cardiac means
"related to the heart" and comes from the Greek
word, kardia, for "heart".
The human heart is about the size of a fist and has a
mass of between 250 and 300 grams. It is about 12
cm long, 9 cm wide, 6 cm thick and located slightly
left of middle in the chest, anterior to the vertebral
column and posterior to the sternum.

3. POSITION OF HEART
The heart rest on the diaphragm near midline of thoracic cavity in
mediastinum. It lies little more to the left than the right, apex is formed
by the tip of the left ventricles & rest on diaphragm, the base of the
heart is its posterior surface it is formed by atria.
ORGANSASSOCIATED WITH THE HEART:
Inferiorly: central tendon of the diaphragm
venacava,
Superiorly: the great blood vessels; aorta, superior
pulmonary artery and vein.
Posteriorly: oesophagus, trachea, bronchus, descending aorta
Laterally: the lungs
Anteriorly: the sternum, ribs and intercostal muscle.

5. STRUCTURE OFTHE HEART
The heart is composed of three layers of tissue pericardium,
myocardium and endocardium;
Pericardium: The pericardium is a triple-layered fluid-filled sac
that surrounds the heart. The outer layer of this sac is the fibrous
pericardium. It is a strong layer of connective tissue. It adheres
to the diaphragm inferiorly, and superiorly it is fused to the roots
of the great vessels that leave and enter the heart. Deep to the
fibrous pericardium is the double layered serous
pericardium. The serous pericardium is a closed sac sandwiched
between the fibrous pericardium and the heart. The outer layer
is the parietal layer of the serous pericardium and adheres to the
inner surface of the fibrous pericardium. The inner visceral layer
of serous pericardium also called as epicardium.

7. Layers of the heart: the wall of heart consist of three
layers:
1) Epicardium (external layer)
2) Myocardium (middle layer)
3) Endocardium (inner layer)
1. Epicardium: It is composed of two tissue layer (outer of
visceral layer of serous pericardium) it is composed of
mesothelium beneath this layer of delicate fibroelastic
tissue and adipose tissue. Epicardium contains blood
vessels, lymphatics and vessels that supply the
myocardium.

8. Myocardium: The myocardium is the basic muscle that
makes up the heart. This muscle is involuntary. The cardiac
muscle structure consists of basic units of cardiac muscle
cells known as myocytes. Coordinated contraction of the
cardiac muscles is what makes the heart propel blood to
various parts of the body. It is the function of the coronary
arteries to supply blood and oxygen to the cardiac muscles.
This is the thickest of all the layers of the heart. The cardiac
muscles cannot afford to rest even for a single second So, it is
absolutely essential that these muscles get blood supply and
nutrition continuously, as any kind of disruption in the blood
and nutrition supply to these muscles can result in death of a
part of the cardiac muscle, which is known as myocardial
infarction or heart attack. This could in turn lead to a
complete cessation of functioning of the heart muscles,
known as cardiac arrest.

9. Endocardium: The endocarium is the innermost, thin and
smooth layer of epithelial tissue that lines the inner surface
of all the heart chambers and valves. This layer is made of
thin and flat cells that are in direct contact with the blood
that flows in and out of the heart. Each heart valve is formed
by a fold of endocardium with connective tissue between the
two layers. However, rather than just being an inner lining of
the heart, the endocardium also has an endocrine function.
This is one of the only layers of the heart that has a single
cell lining that secretes the hormone endocardin, which is
responsible for prolonging myocardial contraction.

10. DIFFERENT VIEWS OF HEART

11. CHAMBERS OF HEART
The heart is a hollow organ divided into four chambers:
⚫Right atrium (entry hall or chambers)
⚫Right ventricle (little bellies)
⚫Left atrium
⚫Left ventricle

12. FOUR CHAMBERS OF HEART

13. The heart is divided into a right and left side by the septum. After
birth blood can not pass through the septum from one side to
another side. Each side is divided by an atrioventricle valve into
an upper chamber , the atrium and lower chamber, the ventricle.
The atrioventricular valves are formed by double folds of
endocardium. The heart consists of four chambers in which blood
flows. Blood enters the right atrium and passes through the right
ventricle. The right ventricle pumps the blood to the lungs where
it becomes oxygenated. The oxygenated blood is brought back to
the heart by the pulmonary veins which enter the left atrium.
From the left atrium blood flows into the left ventricle. The left
ventricle pumps the blood to the aorta which will distribute the
oxygenated blood to all parts of the body.

14. INTERIOR OF HEART

15. STRUCTURE OF HEART:

16. 1. Right Atrium
 The right atrium receives blood from three veins: the
superior vena cava, inferior vena cava and coronary sinus.
 Between right atrium and left atrium thin partition called
interatrial septum.
 Blood passes from right atrium into the right ventricle
through a valve called tricuspid valve also called as right
atrio-ventricular valve.

17. 2. Right Ventricle
 It forms most of the anterior surface of the heart.
 Inside right ventricle contain series of ridges formed by
raised bundles of cardiac muscle fibres called
trabeculae carneae.
 The cusps of the tricuspid valve are connected to tendon
like cords, the chordae tendineae & papillary muscles.
 Right ventricle is separated from left ventricle by
partition called interventricular septum.
 Blood passes from right ventricle through pulmonary
valve into large artery called pulmonary trunk.

18. 3. LeftAtrium
 It forms most of the base of the heart.
 It receives blood from the lungs through four pulmonary
veins.
 Blood passes from the left atrium into the left ventricle
through bicuspid (mitral) valve also called as left atrio-
ventricular valve.

19. 4. Left Ventricle
 Left ventricle forms the apex of the heart.
 Blood passes from left ventricle through aortic valve into
the ascending aorta. Some of the blood in aorta flows into
coronary arteries.
 The remainder blood passes into arch of aorta &
descending aorta (thoracic aorta & abdominal aorta).

20. HEARTVALVES:
Every opening between the chambers and into the vessels is
supplied with a valve that protects backward flow of blood.
⚫The twoAtrioventricular (AV) valves , which are between
the atria and the ventricles;
I. Bicuspid valve (Mitral valve)
II. Tricuspid valve
⚫The two Semilunar (SL) valves, which are in the arteries
leaving the heart;
I. Aortic valve
II. Pulmonary valve

21. Atrioventricular (AV) valves: These are small valves that
prevent backflow from the ventricles into the atrium during
systole. They are anchored to the wall of the ventricle by
chordae tendineae, which prevent the valve from inverting.
The chordae tendineae are attached to papillary muscles that
cause tension to better hold the valve. Together, the papillary
muscles and the chordae
subvalvular apparatus.
tendineae are known as the
The closure of the AV valves is heard as the first heart
sound (HS1).

22. I. Mitral valve: Also known as the "bicuspid valve"
contains two flaps. It allows the blood to flow from the
left atrium into the left ventricle. It is on the left side of
the heart and has two cusps.

23. II. Tricuspid valve: The tricuspid valve is the three-flapped
valve on the right side of the heart, between the right
atrium and the right ventricle which stops the backflow of
blood between the two. It has three cusps.

24. Semilunar valves: These 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
atrioventricularvalves.

25. I. Aortic valve: The aortic valve lies between the left ventricle
and the aorta. The aortic valve has three cusps. During
ventricular systole, pressure rises in the left ventricle.
When the pressure in the left ventricle rises above the
pressure in the aorta, the aortic valve opens, allowing
blood to exit the left ventricle into the aorta. When
ventricular systole ends, pressure in the left ventricle
rapidly drops. When the pressure in the left ventricle
decreases, the aortic pressure forces the aortic valve to
close. The closure of the aortic valve cause second heart
sound (HS2).

26. II. Pulmonary valve: The pulmonary valve (sometimes
referred to as the pulmonic valve) is the semilunar valve
of the heart that lies between the right ventricle and the
pulmonary artery and has three cusps. The closure of the
pulmonary valvecause second heart sound (HS2).

27. STRUCTURE OFV
ALVE
Heart valves are made up of
flaps of thin, strong, tissue
attached to the heart with
fibrous cords called as
cusps. They can only open
in one direction.
functions.
Valves
They
to flow
have two
allow
through
blood
them smoothly
and prevent it from leaking
back against this flow.
Valves allow blood to flow
in onedirection only.

28. 1. Chordae Tendineae: The
chordae tendineae, or heart
strings, are cord-like tendons
that connect the papillary
muscles to the tricuspid valve
and the mitral valve in the
heart.
ventricle
When the right
of the heart
contracts, the blood pressure
pushes the tricuspid valve
which closes and prevents a
backflow of blood into the
right atrium.

29. 2. Papillary Muscles: The
chordae tendinae are
connected to the ventricle
via the papillary muscles,
mitral valve
related
function is
to the
There are two
ventricle.
papillary muscles; medial
and lateral
muscles.
papillary

31. The heart sound

32. Lub
If you listen to your
heartbeat, it makes a
lubdub sound.
The first sound (lub)
happens when the mitral and
tricuspid valves close.
The next sound (dub)
happens when the aortic &
pulmonary valves close after
the blood has been squeezed
out of the heart.
Dub

33. CONDUCTION SYSTEM OF HEART:
The specialized heart cells of the cardiac conduction system
generate and coordinate the transmission of electrical impulses to
the myocardial cells. The result is sequential atrioventricular
contraction, which provides for the most effective flow of blood,
thereby optimizing cardiac output. Three physiologic
characteristics of the cardiac conduction cells account for this
coordination:
⚫Automaticity: ability to initiate an electrical impulse
⚫Excitability: ability to respond to an electrical impulse
⚫Conductivity: ability to transmit an electrical impulse from one cell
toanother

34. The conductionsystem of heart has fourelements;
⚫Sinoatrial (SA) Node
⚫Atrioventricular (AV) Node
⚫Bundleof His
⚫Purkinje Fibers

36. ⚫Sinoatrial node (SA Node): The Sinoatrial node (SA
Node) is the impulse-generating (pacemaker) tissue
located in the right atrium of the heart. It is a group of
cells positioned on the wall of the right atrium, near the
entrance of the superior vena cava. These cells are
modified cardiac myocytes. The SA node has a firing rate
of 60 to 100 impulses per minute, but the rate can change
in response to the metabolic demands of the body. The
impulses cause electrical stimulation and subsequent
contraction of the atria. The impulses are then conducted
to theatrioventricular (AV) node.
⚫The Atrioventricular (AV) node: located in the right
atrial wall near the tricuspid valve) consists of another
group of specialized muscle cells similar to those of the SA
node.

37. The AV node coordinates the incoming electrical impulses
from the atria and, after a slight delay (allowing the atria time
to contract and complete ventricular filling), relays the
impulse to the ventricles. This impulse is then conducted
through a bundle of specialized conduction cells (bundle of
His) that travel in the septum separating the left and right
ventricles.
⚫The bundle of His: divides into the right bundle branch
(conducting impulses to the right ventricle) and the left
bundle branch (conducting impulses to the left ventricle). To
transmit impulses to the largest chamber of the heart, the
left bundle branch bifurcates into the left anterior and left
bundle branches to reach the terminal point in
posterior bundle branches. Impulses travel through the
the
conduction system, called the Purkinje fibers. This is the
point at which the myocardial cells are stimulated, causing
ventricularcontraction.