20/09/2026
The human circulatory system (also known as the cardiovascular system) is the body's main transport network. It delivers oxygen, nutrients, and hormones to cells and removes metabolic waste products like carbon dioxide.
1. Key Components
The Heart: A muscular pump with four chambers—two upper atria and two lower ventricles.
Blood Vessels:
Arteries: Carry oxygen-rich blood away from the heart to the rest of the body (e.g., Aorta). Exception: Pulmonary artery carries deoxygenated blood to the lungs.
Veins: Return oxygen-depleted blood back to the heart (e.g., Vena cava). Exception: Pulmonary vein carries oxygenated blood from the lungs.
Capillaries: Microscopic, thin-walled vessels where the actual exchange of oxygen, nutrients, and waste takes place with cells.
Blood: The transport medium consisting of plasma, red blood cells (RBCs), white blood cells (WBCs), and platelets.
2. How Double Circulation Works
Humans have a double circulation system, meaning blood passes through the heart twice during one complete cycle.Pulmonary Loop (Heart → Lungs → Heart):
Deoxygenated blood enters the Right Atrium \rightarrow passes to the Right Ventricle.
The Right Ventricle pumps blood to the Lungs via the Pulmonary Artery.
In the lungs, blood releases CO_2 and picks up O_2.
Oxygenated blood returns to the Left Atrium via the Pulmonary Vein.
Systemic Loop (Heart → Body → Heart):
Oxygenated blood moves from the Left Atrium \rightarrow Left Ventricle.
The Left Ventricle pumps blood through the Aorta out to the rest of the body.
Cells consume O_2 and deposit CO_2.
Deoxygenated blood travels back through veins into the Right Atrium via the Vena Cava.
Asian Institute of Medical Sciences Indian Council of Medical Research
