Describe double circulation in human beings. Why is it necessary?

Pulmonary Circulation

Pulmonary Circulation

• Pulmonary circulation is the part of the circulatory system that carries deoxygenated blood from the heart to the lungs and returns oxygenated blood back to the heart.
• Deoxygenated blood from the body enters the right atrium of the heart through the superior and inferior vena cava.
• From the right atrium, blood is pumped into the right ventricle and then to the lungs through the pulmonary artery.
• In the lungs, carbon dioxide is removed from the blood, and oxygen is absorbed into the bloodstream.
• Oxygenated blood returns to the heart via the pulmonary veins, entering the left atrium.

• Systemic circulation involves the circulation of oxygenated blood from the heart to the body's tissues and the return of deoxygenated blood back to the heart.
• Oxygenated blood from the left atrium enters the left ventricle and is pumped out to the body through the aorta.
• Blood travels through arteries, arterioles, capillaries (where oxygen and nutrients are exchanged with tissues), venules, and veins.
• Deoxygenated blood returns to the heart through the superior and inferior vena cava, entering the right atrium to complete the cycle.

• Efficiency: Double circulation ensures that oxygenated blood from the lungs is delivered efficiently to the body tissues through systemic circulation without mixing with deoxygenated blood.
• Oxygenation: It allows for the efficient oxygenation of blood. Deoxygenated blood is sent to the lungs for oxygenation before returning to the heart and being distributed to the body.
• Pressure Regulation: Separating the high-pressure systemic circulation from the low-pressure pulmonary circulation helps in regulating blood pressure and preventing overloading of the pulmonary circuit.
• Nutrient and Waste Exchange: It facilitates the exchange of nutrients, gases, and waste products at the capillary level, ensuring proper nourishment of tissues and removal of metabolic wastes.
• Specialized Functions: Double circulation allows for the heart to function effectively in both pumping oxygen-poor blood to the lungs for oxygenation and pumping oxygen-rich blood to the body's tissues for cellular respiration.