Where does gas exchange occur, where O2 poor blood is traded for O2 rich blood?

Gas exchange occurs in the capillaries, which are tiny blood vessels that connect arterioles and venules. These capillaries have very thin walls that allow for the efficient transfer of gases, nutrients, and waste products between the blood and surrounding tissues.

In the lungs, for example, oxygen from inhaled air passes through the capillary walls into the bloodstream, where it attaches to red blood cells, while carbon dioxide from the blood diffuses into the alveoli to be exhaled. This exchange of O2-poor blood for O2-rich blood happens at the capillary level, making them essential for maintaining the body’s oxygen supply and overall homeostasis. The design and function of capillaries are crucial because they provide a large surface area for gas exchange, facilitating the movement of oxygen into the blood and carbon dioxide out of it.