GENERAL HISTOLOGY

Detailed explanation-1: -Tiny air sacs at the end of the bronchioles (tiny branches of air tubes in the lungs). The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.

Detailed explanation-2: -Air sacs are found as tiny sacs off the larger breathing tubes (tracheae) of insects, as extensions of the lungs in birds, and as end organs in the lungs of certain other vertebrates. They serve to increase respiratory efficiency by providing a large surface area for gas exchange.

Detailed explanation-3: -External respiration is another term for gas exchange. It describes both the bulk flow of air into and out of the lungs and the transfer of oxygen and carbon dioxide into the bloodstream through diffusion. Internal respiration, on the other hand, describes the capillary gas exchange in body tissues.

Detailed explanation-4: -An alveolus is an anatomical structure that has the form of a hollow cavity. Its plural is alveoli, from the Latin alveolus, meaning little cavity.