Question

Where does oxygen move from the respiratory system to the circulatory system?

Answer 1

Oxygen is transferred from respiratory system to circulatory system at the level of alveoli and pulmonary capillaries. 97% of oxygen is carried as oxyhemoglobin in blood by RBCs.

Explanation:

Alveoli of lungs are surrounded by extensive blood capillaries. The partial pressure of oxygen in the alveoli is higher than the blood entering the pulmonary capillaries, hence oxygen moves into the blood. Carbon dioxide in the lungs simultaneously diffuses out of the blood into the alveolar space.

The tissues through which gaseous diffusion takes place are:
1. lining of alveolus made of squamous epithelium
2. lining of pulmonary capillary called endothelium .

Two epithelial layers form a sandwich with two basement membranes between them. The barrier dividing air from blood is called respiratory membrane .