Double Circulatory System (Pulmonary and Systemic)

The human body has a double circulatory system, which is made up of two separate cycles, the pulmonary and systemic circulations.
Pulmonary Circulation: This refers to the part of the circulatory system where deoxygenated blood is transported from the heart to the lungs, and oxygenated blood is returned back to the heart.
- Right ventricle pumps deoxygenated blood towards the lungs via the pulmonary artery.
- Within the lungs, oxygen is absorbed into the blood and carbon dioxide, a waste product, is removed during the process of gas exchange.
- This oxygen-rich blood then returns to the left atrium of the heart via the pulmonary veins.
Systemic Circulation: This refers to the cycle where oxygenated blood is transported from the heart to all parts of the body, and deoxygenated blood is transported back to the heart.
- The left ventricle pumps oxygen-rich blood to all body parts (except the lungs) via the aorta. This blood provides oxygen and nutrients to the body cells.
- As the cells use the oxygen and nutrients, they produce carbon dioxide and other waste products.
- This deoxygenated blood, now carrying waste products, returns to the right atrium of the heart via the superior and inferior vena cava.
The two sides of the heart (right and left) are separated by a septum which prevents oxygenated and deoxygenated blood from mixing.
The fact that blood passes through the heart twice in a complete circuit of the body enables it to be pumped at a higher pressure, thereby delivering oxygen throughout the body more efficiently.
The double circulation system is particularly important in warm-blooded animals like humans, where the high metabolic demand requires a fast, efficient supply of oxygen and nutrients.

Remember to understand the flow of blood in the heart and through these two cycles. Diagrams and flowcharts could be a useful way to remember this complex system.