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Reinflation of the alveoli following exhalation is made easier by the surfactant, which reduces surface tension in the thin fluid lining of the alveoli. The fluid coating is produced by the body in order to facilitate the transfer of gases between blood and alveolar air, and the type II cells are typically found at the blood–air barrier. [19 ...
The main reason for exhalation is to rid the body of carbon dioxide, which is the waste product of gas exchange in humans. Air is brought into the lungs through inhalation. Diffusion in the alveoli allows for the exchange of O 2 into the pulmonary capillaries and the removal of CO 2 and other gases from the pulmonary capillaries to be exhaled ...
The process of breathing does not fill the alveoli with atmospheric air during each inhalation (about 350 ml per breath), but the inhaled air is carefully diluted and thoroughly mixed with a large volume of gas (about 2.5 liters in adult humans) known as the functional residual capacity which remains in the lungs after each exhalation, and ...
Type II are larger and they line the alveoli and produce and secrete epithelial lining fluid, and lung surfactant. [34] [32] Type II cells are able to divide and differentiate to Type I cells. [33] The alveolar macrophages have an important role in the immune system. They remove substances which deposit in the alveoli including loose red blood ...
The body's circulatory system transports these gases to and from the cells, where cellular respiration takes place. [2] [3] The breathing of all vertebrates with lungs consists of repetitive cycles of inhalation and exhalation through a highly branched system of tubes or airways which lead from the nose to the alveoli. [4]
The alveoli are the dead end terminals of the "tree", meaning that any air that enters them has to exit via the same route. A system such as this creates dead space, a volume of air (about 150 ml in the adult human) that fills the airways after exhalation and is breathed back into the alveoli before environmental air reaches them.
Macrophages in the alveoli are part of the immune system which engulf and digest any inhaled harmful agents. Hair in the nostrils plays a protective role, trapping particulate matter such as dust. [14] These hairs, called vibrissae, are thicker than body hair and effectively block larger particles from entering the respiratory tract.
They also equalize the pressure in adjacent alveoli and, combined with increased distribution of surfactant, thus play an important role in prevention of collapse of the lung. [ 6 ] Unlike adults, in children these inter-alveolar connections are poorly developed which aids in limiting the spread of infection.