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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 ...
The lowest part of the lung in relation to gravity is called the dependent region. In the dependent region smaller alveolar volumes mean the alveoli are more compliant (more distensible) and so capable of more oxygen exchange. The apex, though showing a higher oxygen partial pressure, ventilates less efficiently since its compliance is lower ...
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. The alveoli are rich with capillaries, called alveolar capillaries.
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. [25]: 489 [31] This lobule is a discrete unit that is the smallest component of the lung that can be seen without aid ...
Alveolar dead space and insufficient perfusion result in a V/Q ratio above 0.8 with decreased fresh oxygen in the alveoli. [1] This might have been caused by blood clotting, heart failure, pulmonary emphysema, or damage in alveolar capillaries. [12] Diagram of pulmonary shunt in alveoli and pulmonary capillary
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. They become alveolar dead space. Zone 2 is the part of the lungs about 3 cm above the heart.
The most notable shared characteristic is the presence of cortical (near the surface) alveoli (sacs).These are flattened vesicles (sacs) arranged as a layer just under the membrane and supporting it, typically contributing to a flexible pellicle (thin skin).
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 ...