In the human body, blood passes through the heart twice in a single complete circuit. This is called Double Circulation — a highly efficient system that keeps oxygenated and deoxygenated blood completely separate.
Two Circuits: Pulmonary + Systemic.
Right Side of Heart: Receives deoxygenated blood, sends to lungs.
Left Side of Heart: Receives oxygenated blood, sends to body.
Advantage: Keeps oxygenated and deoxygenated blood separate.
Found In: Mammals and birds.
1. Pulmonary Circulation (Heart → Lungs → Heart): The right side of the heart pumps deoxygenated blood to the lungs where it picks up oxygen and releases CO₂. The oxygenated blood returns to the left side of the heart.
2. Systemic Circulation (Heart → Body → Heart): The left side of the heart pumps oxygenated blood to all body organs. The deoxygenated blood returns to the right side of the heart.
In fish, blood passes through the heart only once (single circulation), resulting in low blood pressure reaching the body. In humans, the double circuit ensures blood is repressurized in the heart before being sent to the body, maintaining high pressure for efficient delivery to all organs.
Double circulation means blood passes through the heart twice in one complete body circuit — once through the pulmonary circuit (lungs) and once through the systemic circuit (body).
The right side of the heart pumps deoxygenated blood to the lungs.
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