Explain the blood circulation in humans.

Explanation

The main circulatory organ in human is heart. In humans, circulatory system is closed type where blood flows through separate blood vessels, such as arteries, veins, capillaries, etc.
Arteries carry blood from heart to body parts and veins carry blood from various body parts to heart.
In heart, there are four chambers—two atria (upper chamber) and two ventricles (lower chamber). Impure (deoxygenated) blood from various body parts reaches right atrium through superior and inferior vena cava. Blood from right atrium reaches right ventricle from where it gets trans ported to lungs through pulmonary artery. Gaseous exchange takes place in the lungs and oxygenated blood (pure blood) gets transported back to left atrium through pulmonary vein. From left atrium, blood gets collected in left ventricle. Aorta, the main artery then carries oxygenated blood from left ventricle to various body parts.