It includes information regarding human heart.

1. STRUCTURE OF THE
HUMAN HEART
Mrs Suprabha Panda
Assistant Prof. of Zoology
Govt. Degree College for Women
Begumpet

2. Introduction
• The Heart lies in the thoracic cavity between the two
lungs in the mediastinal space and behind the sternum.
• It is directed more to the left than to the right side. The
anterior surface of the heart faces the sternum, the
posterior surface faces the vertebral column and the
interior surface rests on diaphragm.
• The heart is composed of a specialized cardiac muscle
which possesses the special property of automatic
rhythmical contraction.
• The human heart is pinkish about the size of a fist and
weighs approx. 300 gms, the weight in females being
about 25% lesser than the males.

3. The heart is consisting of three layers:
• 1. Pericardium
• 2. Myocardium
• 3. Endocardium
1. Pericardium:
• The heart lies in a double membranous
sac of pericardium with serous fluid
between the two layers(outer parietal
and inner visceral). This is known as
pericardial fluid.
• By its lubricating action, the heart can
move freely or contracts and expands
without any injury. So it allows the easy
movement of the heart. It keeps the heart
moist and absorbs external shock.

4. 2. The Myocardium:
• This is the middle muscular layer. The thickness of the heart
wall is composed of a network of heart muscle fibers which is
known as myocardium.
• The muscular walls of the heart vary in thickness.
• The ventricles have the thickest walls. The walls of the left
ventricles are thicker then those of right ventricle because the
force of contraction of the left ventricle is much greater.
• The walls of the auricle are composed of thinner muscles.
3. Endocardium:
• This is the inner layer of the heart. The heart is lined by
endothelium layer which is known as Endocardium. The valves
attached to the heart are the thickened portions of this
membranes.

5. External structure
• Human heart is four
chambered, consisting of two
atria and two ventricles.
• The left and right atria are
separated externally by a
shallow vertical interatrial
groove.
• The atria are demarcated
externally from the ventricles
by an oblique groove called
atrioventricular sulcus.
• They are coronary sulcus,
anterior inter ventricular
sulcus and posterior inter
ventricular sulcus.
• These have coronary
arteries, through which the
heart receives blood.

7. Internal Structure
1. Atria:
• These are the receiving chambers.
• The two thin walled atria are separated from each other by the interatrial
septum.
• The right atrium receives deoxygenated blood through the openings of
superior vena cava, inferior vena cava and coronary sinus.
• The opening of inferior vena cava is guarded by Eustachian valve.
• The opening of the coronary sinus has coronary or Thebasian valve.
• In the right atrium adjoining the interatrial septum, an oval depression,
the fossa ovalis is present.
• It marks the position of an opening, the foramen ovale, between the two
atria in the foetus, but in the adult it persists only as a depression.
• The left artrium receives oxygenated blood through four openings of
pulmonary veins.
• The artrioventricular opening between the left atrium and the left ventricle
is guarded by the bicuspid valve, also called mitral valve (having two
flaps). The right atrio-ventricular opening is guarded by the tricuspid
valve, as it has three flaps.

8. Internal structure

9. 2.Ventricles:
• These are the pumping chambers.
• The two ventricles are separated by interventricular septum.
• Attached to the flaps of the bicuspid and tricuspid valves are special
fibrous cords, the chordae tendineae, which are joined to the other
ends with the special muscles of the ventricular wall, the papillary
muscles.
• The chordae tendineae prevent the bicuspid and tricuspid valves from
collapsing back into the atria during powerful ventricular contractions.
• The chordae tendineae can be seen extending from the valves to the
columnae carneae, which are the muscular ridges or projections on the
walls of the ventricles.
• The columnae carneae divide the cavity of the ventricles into smaller
spaces, known as fissures.
• The walls of the ventricles are thicker than the atria. The thickest
portion of the human heart is the wall of the left ventricle.

10. • The pulmonary trunk and aorta arise from the right and left
ventricles respectively.
• At the base of the pulmonary trunk and aorta are located three
half-moon shaped pockets known as pulmonary semilunar
valves and aortic semilunar valves respectively.
• These valves allow the free and forward flow of blood, but
prevent any backward flow.
Aorta:
There are two aortas which arise from the heart
1. Systemic aorta: arises from left ventricle which supplies
oxygenated blood to various parts of the body.
2. Pulmonary aorta: arises from right ventricle which carries
deoxygenated blood to the lungs.