Dedicated to my students

1. ANATOMY & PHYSIOLOGY
OF HEART
By:
Mr. Johny Kutty Joseph

2. The Heart
• The heart is a chambered muscular organ that
pumps blood received from the veins into the
arteries, thereby maintaining the flow of blood
through the entire circulatory system.
• It has roughly the size of closed fist.
• It lies in the mediastinum behind sternum
between 4th and 8th thoracic vertebrae.
• This position is convenient for CPR.
• The weight of the heart is 225 to 300 gms in
adults.
• Heart is transverse in shape for children but it has
normal pyramidal shape in adults by 25 years.

3. The Heart: Location
• The pointed apex is
formed by the tip of the
left ventricle and rests
on the diaphragm.
• The inferior border also
rests on the diaphragm.
• The superior border is
at pulmonary trunk and
arch of the aorta.
• It is between the lungs
and posterior to
sternum and ribs.

4. Coverings of Heart
• The heart is surrounded by
membrane called Pericardium.
• The pericardium is a fibroserous
sac that encloses the heart and
the roots of the great vessels.
• The pericardium lies within the
middle mediastinum.
• Its function is to restrict
excessive movements of the
heart as a whole and to serve as
a lubricated container in which
the different parts of the heart
can contract.

5. Coverings of Heart
• Pericardium – a double-walled sac
around the heart composed of:
1. A superficial fibrous
pericardium
2. A deep two-layer serous
pericardium
The parietal layer lines the
internal surface of the fibrous
pericardium
The visceral layer or
epicardium lines the surface of
the heart
• They are separated by the fluid-
filled pericardial cavity.

6. Structure of Heart

7. Wall of the Heart
Three distinct layer of tissues make up the heart
wall. They are:
• Epicardium – visceral layer of the serous
pericardium.
• Myocardium – cardiac muscle layer forming the
bulk of the heart.
• Endocardium – endothelial layer of the inner
myocardial surface
In addition Fibrous skeleton of the heart –
crisscrossing, interlacing layer of connective tissue
also makes up the structure of heart.

8. Structure of Heart Wall

9. • Epicardium: The outer layer of the heart. The term
epicardium means “on the heart”. This is the visceral
layer of the pericardium called as serous pericardium.
• Myocardioum:
a. This is the thick, contractile, middle layer of the heart.
b. This has arranged cardiac muscles.
c. They possess interconnected muscle cell junctions
called syncytium for the electrical connections to
work. It can pass an action potential from fiber to
fiber.
d. The interconnected muscle fibers also helps to hold
the high pressured blood strongly inside the heart.
e. Myocardium is damaged in case of MI and cardiac
arrest.

10. • Endocardium:
a. It is a delicate layer of the interior of heart called as
endocardium.
b. This is made of endothelial tissues. It continues to all
the blood vessels.
c. It also cover the beam like projections of myocardial
tissue. These projections are called trabeculae
carneae and it helps to add force to the contraction
of heart.
d. Inward folds or pockets formed by the endocardium
and connective tissues are called valves (AV & SL)
which prevents the return flow of the blood. There
are tricuspid valves and bicuspid valves.

11. The Heart Chambers
• The heart consists of four chambers.
• Two superior receiving chamber (atria) and two
inferior pumping chamber (ventricles).
• The atria receive blood from veins and
ventricles pump blood to arteries.
• On the anterior part of atria there is a wrinkled
pouch like structure called auricle which
increases the capacity of atria during
conduction.
• The surface of the heart are a series of grooves
called sulci which contain coronary artery and
fat.

12. The Heart Chambers
Right atrium:
• Right border of the heart.
• It receives blood from three veins; superior vena cava,
inferior vena cava and coronary sinus.
• Between the right atrium and left atrium a thin
partition called interatrial septum.
• An oval depression is present in this septum called
fossa ovalis, the remnant of foramen ovale of fetal
heart. It closes at birth.
• The valve between right atrium and right ventricle is
called tricuspid valve/right atrioventricular valve. It is
made of dense cusps of connective tissue.

13. The Right Atrium

14. The Right Ventricle
• Receives blood from the right atrium through the tricuspid
valve .
• The edges of the valve cusps are attached to chordae
tendineae which are, in turn, attached below to papillary
muscles.
• The wall of the right ventricle is thicker than that of the atria
but not as thick as that of the left ventricle.
• The wall contains a mass of muscular bundles known as
trabeculae carneae.
• The pulmonary valve is situated at the top of the
infundibulum.
• It is composed of three semilunar cusps.
• Blood flows through the valve and into the pulmonary
arteries via the pulmonary trunk to be oxygenated in the
lungs.

15. The Right Ventricle

16. The Left Atrium
• Receives oxygenated
blood from four
pulmonary veins.
• The walls are same
thick as right atrium.
• The mitral (bicuspid)
/ left
atrioventricular
valve guards the
passage of blood
from the left atrium
to the left ventricle.

17. The Left Ventricle
• The wall of the left ventricle is thicker than the right
ventricle but the structure is similar. This is the thickest
chamber of the heart.
• It forms the apex of the heart.
• Like the right ventricle it also contains Trabeculae carneae
and chordae tendineae that anchor the cusps to papillary
muscles.
• Blood pass from the aortic valve/semilunar valve into the
ascending aorta.
• A branch of the ascending aorta called coronary artery
provides blood supply to the cardiac tissues.
• During fetal life a temporary blood vessel called ductus
arteriosus shunts the blood from pulmonary trunk to aorta.
It closes after birth. Hence a small amount of blood enter
baby lungs.
• The thick wall is necessary to pump oxygenated blood at
high pressure through the systemic circulation.

18. The Left Ventricle

19. The Heart Valves
• Right AV (Tricuspid):
Separates the right
atrium from the right
ventricle. Prevents
backflow into atrium.
• Left AV (Bicuspid):
Separates the left atrium
from the left ventricle.
Prevents backflow into
atrium.
• Pulmonary valve:
Separates the right
ventricle from the
pulmonary arteries.
Prevents backflow after
ventricular contraction.
• Aortic valve: Separates
the left ventricle from
the aorta. Prevents
backflow after
ventricular contraction.
Atrio-ventricular valves Semi-lunar valves
• All the valves are constructed in uni-direction blood
flow.
• These valves are opened and closed on demand.

20. Blood flow through heart.
• The blood flow starts from right atrium.
• Then it flows to right ventricle through atrio-ventricular
/ tricuspid valve.
• From right ventricle it flows through pulmonary
semilunar valves into the pulmonary artery and then to
pulmonary trunk.
• The pulmonary trunk branches to form right and left
pulmonary artery for gas exchange at left and right
lungs.
• From lungs the oxygenated blood comes to left atrium
through pulmonary veins.
• From left atrium blood flows through mitral valve/left
atrio-ventricular/bicuspid valve to left ventricle.

21. Blood flow through heart.
• From left ventricle blood
is pumped to aorta
through aortic valve then
the supply goes to
different branches to
different parts of the
body.
• The venous drainage from
different parts of the
body brings deoxygenated
blood back to right atrium
through inferior vena cava
and superior vena cava.

22. Arterial Supply of the Heart
• Myocardial cells receive blood
supply from coronary arteries
both right and left.
• The closure of aortic valve
during ventricular relaxation
prevents the backflow of the
blood and fills the coronary
artery.
• The arterial supply of the heart
is provided by the right and left
coronary arteries, which arise
from the ascending aorta
immediately above the aortic
valve.

23. Branches of Coronary Arteries
1. Right Coronary artery: Branches
– Right marginal arteries.
– Posterior inter-ventricular artery.
– Posterior septal artery
– Atrio-ventricular nodal artery.
2. Left Coronary artery: Branches
– Left Marginal artery.
– Anterior interventricular artery.
– Anterior septal artery
– Circumflex artery.

24. Coronary Arteries
1. Both ventricles receive
blood supply from both
branches.
2. Most abundant blood
supply goes to myocardium
of left ventricle.
3. People may have either left
or right coronary artery
dominant in the body.
4. An anastomosis occurs
among branches of arteries.
This helps in collateral
circulation. The lack of
anastomosis can cause MI.

25. Venous Drainage of the Heart
• Most venous blood from
the coronary capillaries
drain into the coronary
sinus ,which lies in the
posterior part of the
atrio-ventricular groove .
• Some veins do not enter
the sinus rather it drain
the venous blood directly
into right atrium with
inferior vena cava.
• Veins and arteries are
parallel.

26. Nerve Supply of the Heart
• The myocardium is auto rhythmic and hence can produce
its own action potential.
• To coordinate self activation mechanism the specialized
myocardial fibers are present called as conduction system
of the heart.
• The heart is innervated by sympathetic and
parasympathetic fibers of the autonomic nervous system
via the cardiac plexuses situated below the arch of the
aorta. This is to meet the unexpected regulations and
needs.
• The sympathetic supply arises from the cervical and upper
thoracic portions of the sympathetic trunks, and the
parasympathetic supply comes from the Vagus nerves.

27. CONDUCTING SYSTEM OF THE HEART
• The rhythmical electrical activity is the reason for the
heart’s lifelong beat.
• The source of the electrical activity is a network of
specialized cardiac muscles fibers called auto-rhytmic fibers
because they are self excitable.
• Cardiac muscle tissue has intrinsic ability to generate and
conduct impulses and signals these cells to contract
rhythmically.
• They continue to stimulate a heart beat even after it is
removed from the body. (heart transplantation)
• They act as pacemakers.
• The cardiac conduction system is rhythmic that it ensures
that the cardiac chambers are stimulated to contract in a
coordinated manner.

28. CONDUCTING SYSTEM OF THE HEART
• Fibers that initiate signals are called pacemaker
fibers.
• During resting membrane potential these fibers leak
K+ ions and attract Na+ and Ca++ ions inward.
• This depolarizes the membrane eventually reaching
to threshold potential.
• It happens continuously hence creating intrinsic
rhythm.
• The syncytium helps in transferring this impulses.
• Some cardiac muscles are specially structured to not
to be contractile, instead permit rapid generation and
conduction of action potential.

29. CONDUCTING SYSTEM OF THE HEART

30. STEPS IN CONDUCTION
• Four structures make the electrical conduction of the
heart; such as;
a. Sinoatrial node (SA node)
b. Atrioventricular (AV) node
c. Atriventricular (AV) bundle/Bundle of His
d. Subendocardial branches (Purkinje fibers)
• The cardiac excitation normally begin in the sinoatrial
(SA) node.
• SA node is located in the right arterial wall near to
superior vena cava.
• SA node do not have a stable resting potential rather it
depolarize to threshold spontaneously. This act as
pacemaker potential.

31. STEPS IN CONDUCTION
• As the pacemaker potential reaches the threshold it
triggers action potential from SA node to all atria
through gap junctions to interrelated discs and
muscles and to AV node.
• As a result the two atria contract at the same time.
• Action potential reaches Atrio-ventricular (AV) node
from SA node. It is located in the intra-arterial
septum near to coronary sinuses.
• The cellular structure of AV node is different from SA
node hence it delays the action potential transmission
allowing both atria to empty the blood to ventricles.

32. STEPS IN CONDUCTION
• From AV node the action potential enters AV bundle /
bundle of His.
• This is the only place where the action potential is
transferred from Atria to Ventricle. The electrical
transmission is not possible through gap junction as there
is a electrical insulation by fibrous skeleton.
• After propagating along AV bundle it enters right and left
bundle branches. This bundle pass through inter-
ventricular septum towards the apex of the heart.
• Finally the large diameter Purkinje fibers rapidly conduct
the action potential beginning at the apex of the heart
upward to the ventricle and terminates.
• This pushes blood into the semi lunar valves.

33. STEPS IN CONDUCTION
• The SA node is natural pacemaker which performs
under the influence of autonomic and endocrine
controls.
• The normal discharge rate of SA node is 70-75
beats/minutes.
• In case of the failure of SA node to create impulse it
may get transferred to AV bundle or Purkinje fibers
but the rate will be lesser.
• This type of transfer is called ectopic transfer which
is abnormal for the body and exhibited by decreased
pulse rate such as 40 to 60 beats/mts.

34. ACTION POTENTIAL AND CONTARCTION
• The Action Potential initiated by the SA node travels
along with the conduction system and excite the atrial
and ventricular contractile fibers of myocardium.
a. Depolarization: The contractile fibers have -90mV
resting potential. By the inflow of Na+ ions through
channels will create rapid depolarization.
b. Plateau: The next phase. It is the maintenance of
depolarization. It is due to inflow of Ca++ions at an
increased rate which in-turn triggers contraction.
This is also supported by K+ ions through voltage
gated channels.
c. Re-polarization: It is the recovery of the resting
potential. This is by the outflow of Na+, Ca++, and
K+ ions.

35. ACTION POTENTIAL AND CONTARCTION
• The refractory period in cardiac muscle lasts longer
than skeletal muscle. As a result another contraction
cannot begin unless well relaxed. This helps the
proper filling of chambers of the heart.
• If the refractory period is lesser then the heart will
cease to flow the blood.

36. THANK YOU