Capillaries function in gas exchange. Describe at least two ways capillary structure is related to this function.

The main function of the respiratory system is the exchange of oxygen and carbon dioxide. Inhaled oxygen penetrates the lungs and reaches the alveoli. The layers of cells lining the alveoli and surrounding capillaries are arranged occupying the thickness of a single cell and are in close contact with each other. This barrier between air and blood is approximately one micron thick (1 / 10,000 cm). Oxygen quickly crosses this air - blood barrier and reaches the blood that circulates through the capillaries. Similarly, carbon dioxide passes from the blood into the alveoli, from where it is exhaled outside.