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This marks the beginning of the terminal respiratory unit called the acinus which includes the respiratory bronchioles, the alveolar ducts, alveolar sacs, and alveoli. [27] An acinus measures up to 10 mm in diameter. [28] A primary pulmonary lobule is the part of the lung distal to the respiratory bronchiole. [29]
An acinus (/ ˈ æ s ɪ n ə s /; pl.: ... where the secretion is produced, is acinar in form, as is the alveolar sac containing multiple alveoli in the lungs ...
Almost any type of lung tumor or lung cancer can compress the alveoli and reduce gas exchange capacity. In some cases the tumor will fill the alveoli. [33] Cavitary pneumonia is a process in which the alveoli are destroyed and produce a cavity. As the alveoli are destroyed, the surface area for gas exchange to occur becomes reduced.
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.
In anatomy, a lobe is a clear anatomical division or extension [1] of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to the much smaller lobule, which is a clear division only visible under the microscope. [2]
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 ventilation/perfusion ratio (V/Q ratio) is higher in zone #1 (the apex of lung) when a person is standing than it is in zone #3 (the base of lung) because perfusion is nearly absent. However, ventilation and perfusion are highest in base of the lung, resulting in a comparatively lower V/Q ratio.
Panlobular emphysema, also called panacinar emphysema, affects all of the alveoli in a lobule, and can involve the whole lung or mainly the lower lobes. [18] [24] This type of emphysema is associated with alpha-1 antitrypsin deficiency (A1AD or AATD), and Ritalin lung, [24] and is not related to smoking. [18]