How is blood oxygenated in the body?

Oxygenation of blood occurs in the alveoli and capillaries of the lungs, making this the correct choice. When we breathe in, air enters the lungs and fills tiny air sacs called alveoli. Here, oxygen from the air passes through the alveolar walls and into the surrounding capillaries, which are small blood vessels. This process is facilitated by diffusion—oxygen moves from an area of higher concentration in the alveoli to an area of lower concentration in the blood.

Once in the capillaries, oxygen binds to hemoglobin molecules within red blood cells, allowing the oxygen to be transported throughout the body. This is essential for cellular respiration, where oxygen is used by cells to produce energy. The oxygenated blood is then carried back to the heart, from where it is pumped to the rest of the body.

Options that mention veins and arteries, the heart's chambers, or the liver do not accurately describe the primary physiological process responsible for blood oxygenation. While veins and arteries play important roles in circulation, they do not partake in the actual gas exchange process. Similarly, the heart's chambers are responsible for pumping blood but do not directly facilitate the exchange of oxygen and carbon dioxide. The liver's function is primarily in metabolism and