As a subject matter expert in respiratory physiology, I can explain the process of oxygen entering the bloodstream. Oxygen enters the bloodstream through the alveoli in the lungs. Here's a step-by-step description:


1. Inhalation: When you breathe in, air containing oxygen is drawn into the lungs.

2. Gas Exchange: The inhaled air reaches the alveoli, which are tiny air sacs surrounded by a network of capillaries.

3. Diffusion: Oxygen from the alveoli diffuses across the thin walls of the alveoli and the capillaries into the red blood cells (erythrocytes) within the capillaries. This process is facilitated by the large surface area of the alveoli and the thinness of the alveolar and capillary walls, which are only one cell thick.

4. Binding to Hemoglobin: Once in the red blood cells, oxygen binds to a protein called hemoglobin, which gives blood its red color.

5. Circulation: The oxygen-rich blood is then pumped by the heart through the arteries to the rest of the body.

read more >>

The oxygen enters the bloodstream from the alveoli, tiny sacs in the lungs where gas exchange takes place (Figure below). The transfer of oxygen into the blood is through simple diffusion. The oxygen-rich blood returns to the heart.read more >>