Detailed Summary
Double circulation is a vital feature of the circulatory system in humans and other mammals, characterized by two distinct pathways of blood flow: pulmonary circulation and systemic circulation. In this arrangement, blood pumped from the right ventricle enters the pulmonary artery, which leads to the lungs. Here, the deoxygenated blood releases carbon dioxide and picks up oxygen, becoming oxygenated.
Once oxygenated, the blood travels back to the left atrium through the pulmonary veins. From the left atrium, blood moves into the left ventricle, which pumps it into the aorta for distribution throughout the body via systemic circulation.
During systemic circulation, the oxygen-rich blood travels through increasingly smaller arteries and arterioles until it reaches capillaries, where nutrients and oxygen are exchanged for carbon dioxide and metabolic waste at the cellular level. The deoxygenated blood is then collected by venules and veins and returned to the right atrium via the superior and inferior vena cava, completing the circuit.
Double circulation is crucial as it allows for efficient separation of oxygenated and deoxygenated blood, facilitating sustained high metabolic activities typical in mammals. The presence of two circuits not only optimizes gas exchange but also ensures that tissues receive a continuous supply of nutrients and oxygen. Additionally, in the human body, there is a unique vascular connection known as the hepatic portal system, which transports blood from the digestive tract to the liver for filtration before entering systemic circulation.