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A pulmonary alveolus (pl. alveoli; from Latin alveolus 'little cavity'), also called an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where pulmonary gas exchange takes place. [1] Oxygen is exchanged for carbon dioxide at the blood–air barrier between the alveolar air and the pulmonary ...
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.
Micrograph showing hemosiderin-laden alveolar macrophages, as seen in a pulmonary hemorrhage. H&E stain. An alveolar macrophage, pulmonary macrophage, (or dust cell) is a type of macrophage, a professional phagocyte, found in the airways and at the level of the alveoli in the lungs, but separated from their walls. [1]
The tendency for the alveoli to collapse is therefore almost the same at the end of exhalation as at the end of inhalation. Thirdly, the surface tension of the curved watery layer lining the alveoli tends to draw water from the lung tissues into the alveoli. Surfactant reduces this danger to negligible levels, and keeps the alveoli dry. [6] [37]
The major function of the lungs is gas exchange between the lungs and the blood. [67] The alveolar and pulmonary capillary gases equilibrate across the thin blood–air barrier . [ 34 ] [ 68 ] [ 69 ] This thin membrane (about 0.5 –2 μm thick) is folded into about 300 million alveoli, providing an extremely large surface area (estimates ...
Emphysema. Collateral ventilation is a back-up system of alveolar ventilation that can bypass the normal route of airflow when airways are restricted or obstructed. The pathways involved include those between adjacent alveoli (pores of Kohn), between bronchioles and alveoli (canals of Lambert), and those between bronchioles (channels of Martin).
A lobule of the lung enclosed in septa and supplied by a terminal bronchiole that branches into the respiratory bronchioles. Each respiratory bronchiole supplies the alveoli held in each acinus accompanied by a pulmonary artery branch. The pulmonary lobule is the portion of the lung ventilated by one bronchiole.
Elastic recoil is inversely related to lung compliance. This phenomenon occurs because of the elastin in the elastic fibers in the connective tissue of the lungs, and because of the surface tension of the film of fluid that lines the alveoli. As water molecules pull together, they also pull on the alveolar walls causing the alveoli to recoil ...