The human heart is a biological pump located in the chest cavity that circulates blood through the cardiovascular system. It is composed of four chambers - two upper atria and two lower ventricles separated by partitions to prevent mixing of oxygenated and deoxygenated blood. The right atrium receives blood from veins and pumps it to the right ventricle to be sent to the lungs, while the left atrium receives oxygenated blood from the lungs and pumps it to the left ventricle to be circulated through the body. The heart is surrounded by membranes called pericardium for protection and support.

1. 1
The Cardiovascular System: Anatomy of Human Heart
Dr.S.Krishnamoorthy
Assistant Professor of Zoology,
PG and Research Centre in Zoology,
Vivekananda College, Tiruvedakam West, Madurai

2. Introduction
 Human heart is basically a biological pump that circulates blood in the
human body. The heart is the size of a human fist and is located
between the lungs in the thoracic cavity, slightly towards the left of the
sternum (breastbone). It forms the cardiovascular system together with
blood vessels, veins and capillaries.
 The blood is carried through arteries, arterioles and capillaries to the
body whereas, blood is returned to the heart through venules and veins.
The human heart is made of four chambers i.e., two upper left and right
atria and two lower left and right ventricle.

4. Chambers of Heart
 To avoid the mix of blood rich in oxygen and carbon dioxide. Human
heart has four chambers. There is a partition between the two chambers
which does not allow the mix of blood.
 Right Atrium: These are called as blood receiving chambers. It receives
blood from veins and pump it to right ventricle.
 Right Ventricle: It receives blood from the right atrium and pump it to
the lungs.
 Left Atrium: It receives oxygenated blood from the lungs and pump it
to the left ventricle.
 Left Ventricle: It pumps blood to the rest of the body.

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

6. 6
Pericardial Layers of the Heart

7. Cardiac Muscles

8. Nodal tissues in heart
 There is a thin wall called interatrial septum that separates the right and
left atria. Also, there is a thick wall called as inter ventricular septum
that separates the left and right ventricles. The same side of the atria
and ventricle are separated by fibrous tissue known as atrio-ventricular
septum. There is an opening between the right atrium and right
ventricle guarded by valves known as flaps or cusps. The tissue present
in the upper right atrium is called as sinoatrial node( SAN). Whereas,
the other tissue is seen in the left corner of the right atrium known as
atrio-ventricular node (AVN).

9. Nodal tissues of heart

10. Blood Circulation in Human Heart

13. Facts about Human Heart
 Some of the facts about the human heart are as follows:
 The size of the human heart is similar to size of closed fist.
 The weight of the heart is around 280-340 grams in men and 230-280
gram in female.
 The heart beat in human is about 1,00,000 times per day.
 For adult, heart beat is 60-80 times per minute.
 The newborns heart beats are much faster then adults which is around
70-190 per minute.