The document provides an overview of the physiology of the heart, detailing its location, size, and structure, which includes four chambers and three layers: epicardium, myocardium, and endocardium. It explains the heart's functions in blood circulation, regulating heartbeat rhythm, and maintaining blood pressure, as well as the phases of the cardiac cycle. Additional information covers the heart's role in hormone regulation and electrocardiogram generation.

1. PHYSIOLOGY OF THE HEART
BY
T,C.Kaviya
Assistance Professor
Department of Hospital Administration

2. Introduction:
The physiology of the heart refers to
the study of how the heart functions to
pump blood, deliver oxygen and nutrients
to tissues, and maintain circulatory
homeostasis in the body. It involves the
electrical and mechanical processes that
control heart activity, blood flow, and
coordination between the heart's chambers.

3. Location:
1. Thoracic cavity (chest
cavity)
2. Medial (middle) andanterior
(front) part of the thorax
3. Between the lungs, slightly
offset to the left4. Behind
the sternum (breastbone)
and ribcage5. In front of the
trachea, esophagus, and
spine

4. Size:
1. Adult heart: Approximately 12 cm (5 inches)
long, 8 cm (3 inches) wide, and 6 cm (2.5
inches) thick
2. Weight: Approximately 250-300 grams (8.8-10.6
ounces)3. Volume: Approximately 500-600
milliliters (17-20 ounces)

5. Heart Position:
1. Obliquely placed, with the apex
pointing downwards and to the
left
2. Slightly rotated to the left, with
the right border parallel to the
sternum

6. Structure of the Heart
Chambers of the heart:
The heart is a muscular organ with four chambers:
Right Atrium: Receives deoxygenated blood from the body via the
superior and inferior vena cava.
Right Ventricle: Pumps deoxygenated blood to the lungs via the
pulmonary artery.
Left Atrium: Receives oxygenated blood from the lungs via the
pulmonary veins.
Left Ventricle: Pumps oxygenated blood to the rest of the body via the
aorta.
The heart also contains valves (tricuspid, mitral, pulmonary, and aortic)
that prevent backflow and ensure the unidirectional flow of blood.

7. Chambers ot the heart:
The heart is made up of three distinct layers, each serving a
specific function that is vital to the heart's ability to pump
blood effectively. These layers are:
Epicardium
Description: The outermost layer of the heart.
Structure: It is a thin layer of connective tissue and
epithelial cells that also forms part of the pericardium (the
sac surrounding the heart).
Function:
The epicardium serves as a protective outer layer.
It contains blood vessels, nerves, and lymphatics that
supply the myocardium.
It also acts as a lubricating surface to reduce friction
between the heart and surrounding structures as the heart
beats.

8. Myocardium
Description: The middle, thickest, and most muscular layer of
the heart.
Structure: Composed mainly of cardiac muscle fibers
(myocytes) arranged in a spiral or helical pattern that enables
effective contraction.
Function:
It is responsible for the heart’s pumping action. The
myocardial tissue contracts and relaxes in response to
electrical signals, which allows the heart to pump blood
through the circulatory system.
The myocardium is the thickest in the left ventricle
because it must pump blood throughout the entire body,
whereas the myocardium in the right ventricle is thinner
as it only pumps blood to the lungs.

9. Endocardium
Description: The innermost layer of the heart.
Structure: A thin, smooth membrane composed of
endothelial cells (similar to the lining of blood
vessels) and underlying connective tissue.
Function:
It lines the inner chambers of the heart, including
the heart valves.
It provides a smooth surface for blood to flow
over, which helps prevent blood clots and reduces
friction.
The endocardium also plays a role in maintaining
the electrical system of the heart, as it surrounds
the heart’s conduction tissues.

10. Pumping Blood:
 Receiving deoxygenated
blood from the body
through the veins
 Pumping oxygenated
blood from the lungs to
the body through the
arteries
 Maintaining blood
pressure

11. Cardiac Cycle:
1. Diastole: Relaxation and
filling of heart chambers
2. Systole: Contraction and
pumping of blood

12. Heart Functions:
1. Atrial Function: Receiving blood and
pumping it to the ventricles
2. Ventricular Function: Pumping blood to the
lungs and body
3. Sinoatrial (SA) Node Function: Regulating
heartbeat rhythm4. Atrioventricular (AV)
Node Function: Coordinating atrial and
ventricular contractions

13. Blood Circulation:
1. Pulmonary circulation: Heart to lungs
and back
2. Systemic circulation: Heart to body
and back

14. Regulation of Blood
Pressure:
1. Heart rate regulation
2. Stroke volume
regulation
3. Vasodilation and
vasoconstriction

15. Other Functions:
1. Hormone regulation (e.g., atrial natriuretic
peptide)
2. Electrocardiogram (ECG) generation
3. Maintenance of blood pH levels

16. THANK YOU