CBSE · Class 10 · Science · Life ProcessesDescribe the internal structure and working mechanism of the human heart. Explain how blood circulation takes place through the heart (Double Circulation).

Introduction to Human Heart

1. The human heart is a muscular organ roughly the size of a fist, located in the chest cavity slightly towards the left.
2. Its primary function is to pump blood throughout the body to supply oxygen and nutrients while collecting carbon dioxide and metabolic wastes.

Internal Structure of the Heart

• Four Chambers: The heart is divided into four chambers to prevent the mixing of oxygenated and deoxygenated blood:
  • Atria (Upper Chambers): Right Atrium and Left Atrium. They act as receiving chambers.
  • Ventricles (Lower Chambers): Right Ventricle and Left Ventricle. They act as pumping chambers with thicker muscular walls.
• Septum: A muscular wall that separates the left and right sides of the heart completely.
• Valves: Tricuspid valve (between right atrium and right ventricle) and Bicuspid/Mitral valve (between left atrium and left ventricle) prevent the backflow of blood. Semilunar valves are present at the base of arteries leaving the heart.

Mechanism of Working and Double Circulation\nBlood passes through the heart twice during each complete cycle, which is known as Double Circulation. It consists of two pathways:

1. Pulmonary Circulation (Right Side of Heart):

   • Deoxygenated blood from various body parts is collected by two large veins called Vena Cava and poured into the Right Atrium.
   • When the right atrium contracts, blood is pushed into the Right Ventricle through the tricuspid valve.
   • From the right ventricle, blood is pumped into the Pulmonary Artery, which carries it to the lungs.
   • In the lungs, carbon dioxide is released, and fresh oxygen is absorbed by the blood.

2. Systemic Circulation (Left Side of Heart):

   • Oxygenated blood from the lungs returns to the Left Atrium via the pulmonary veins.
   • Contraction of the left atrium forces blood into the Left Ventricle through the bicuspid valve.
   • The left ventricle, having the thickest muscular walls, pumps oxygenated blood with high pressure into the Aorta, the body's largest artery.
   • The aorta distributes oxygenated blood to all parts of the body.

Significance of Double Circulation

• Double circulation ensures complete segregation of oxygenated and deoxygenated blood.
• This efficient system allows a high supply of oxygen to meet the high energy needs of warm-blooded animals like birds and mammals to maintain their body temperature.