Once inside the lungs, these arteries split into increasingly smaller branches that eventually reach the pulmonary capillary beds, which wrap around the alveoli of the lungs. This is the site of

This is the site of gaseous exchange

Explanation:

Gaseous exchange is the mechanism by which oxygen is substituted for CO₂ in the body. CO₂ laden blood is carried to the alveoli, which is wrapped with numerous capillary beds and with walls that are thin. When a person inhales, the difference in the partial pressure of the various gases ( oxygen and carbon dioxide) causes them t move down their concentration gradients, with CO₂ diffusion into the lungs from red blood cells, and oxygen binding to the haemoglobin in the red blood cells, after which they are carried to all body tissues for cellular respiration. During exhalation, the CO₂ in the lungs is expelled to the exterior and the process repeats.