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A pulmonary alveolus (‹The template Plural abbr is being considered for merging.› 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]
In normal health pulmonary arterial (Pa) pressure exceeds alveolar pressure (PA) in all parts of the lung. It is generally only observed when a person is ventilated with positive pressure or hemorrhage. In these circumstances, blood vessels can become completely collapsed by alveolar pressure (PA) and blood does not flow through these regions.
The alveoli are tiny air sacs in the lungs where gas exchange takes place. The mean number of alveoli in a human lung is 480 million. [11] When the diaphragm contracts, a negative pressure is generated in the thorax and air rushes in to fill the cavity. When that happens, these sacs fill with air, making the lung expand.
A primary pulmonary lobule is the part of the lung distal to the respiratory bronchiole. [29] Thus, it includes the alveolar ducts, sacs, and alveoli but not the respiratory bronchioles. [30] The unit described as the secondary pulmonary lobule is the lobule most referred to as the pulmonary lobule or respiratory lobule.
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]
Pulmonary surfactant is a surface-active complex of phospholipids and proteins formed by type II alveolar cells. [1] The proteins and lipids that make up the surfactant have both hydrophilic and hydrophobic regions.
Pulmonary alveolus, an air sac in the lungs Alveolar cell or pneumocyte; Alveolar duct; Alveolar macrophage; Mammary alveolus, a milk sac in the mammary glands; Alveolar gland; Dental alveolus, also known as "tooth socket", a socket in the jaw that holds the roots of teeth Alveolar ridge, the jaw structure that contains the dental alveoli ...
The pleural cavity, or pleural space (or sometimes intrapleural space), is the potential space between the pleurae of the pleural sac that surrounds each lung.A small amount of serous pleural fluid is maintained in the pleural cavity to enable lubrication between the membranes, and also to create a pressure gradient.