Structure of Human Heart | Urdu/Hindi

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Published Feb 4, 2025

Structure of the Human Heart
The human heart is a muscular organ located slightly left of the midline behind the sternum. It is enclosed by a protective covering called the pericardium, which consists of two layers:
• Fibrous Pericardium: Outer thick layer for mechanical protection.
• Serous Pericardium: Inner layer with pericardial fluid that reduces friction during contractions.
The heart wall has three layers:
1. Epicardium: Outer layer.
2. Myocardium: Thick muscular middle layer responsible for contractions.
3. Endocardium: Inner smooth layer.
Structure of the Heart
The heart is divided into four chambers:
Atria (Upper chambers):
o Right Atrium: Receives deoxygenated blood from the body via the superior and inferior vena cava.
o Left Atrium: Receives oxygenated blood from the lungs via pulmonary veins.
Ventricles (Lower chambers):
o Right Ventricle: Pumps blood to the lungs through the pulmonary artery.
o Left Ventricle: Pumps oxygenated blood to the body through the systemic aorta.
Valves of the Heart
• Atrioventricular (AV) Valves:
o Tricuspid Valve: Between the right atrium and right ventricle.
o Bicuspid (Mitral) Valve: Between the left atrium and left ventricle.
• Semilunar Valves:
o Pulmonary Valve: At the exit of the right ventricle.
o Aortic Valve: At the exit of the left ventricle.
These valves prevent the backward flow of blood. The AV valves are anchored by chordae tendineae to prevent inversion.

Phases of Heartbeat
The rhythmic contraction and relaxation of heart chambers are known as the cardiac cycle. A complete cycle includes:
Atrial Systole: Both atria contract simultaneously, pumping blood into the ventricles.
Ventricular Systole: Both ventricles contract, pumping blood into the aorta and pulmonary artery.
Diastole: The chambers relax, allowing blood to flow in from the veins.
1. The heart rate is about 72 beats per minute at rest.
2. The "lub-dub" sound of the heartbeat is caused by:
a. "Lub": Closing of AV valves during ventricular contraction.
b. "Dub": Closing of semilunar valves during relaxation.

Conduction System of the Heart
1. SA Node (Sinoatrial Node):
a. Acts as the pacemaker, generating electrical impulses that cause the atria to contract.
2. AV Node (Atrioventricular Node):
a. Delays the impulse to ensure atria empty blood before ventricles contract.
3. Bundle of His and Purkinje Fibers:
a. Spread impulses to all parts of the ventricles, ensuring coordinated contraction.