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The cells in the respiratory epithelium are of five main types: a) ciliated cells, b) goblet cells, c) brush cells, d) airway basal cells, and e) small granule cells (NDES) [6] Goblet cells become increasingly fewer further down the respiratory tree until they are absent in the terminal bronchioles; club cells take over their role to some extent here. [7]
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.
The respiratory bronchioles deliver air to the exchange surfaces of the lungs. [5] They are interrupted by alveoli which are thin walled evaginations. Alveolar ducts are side branches of the respiratory bronchioles. The respiratory bronchioles are lined by ciliated cuboidal epithelium along with some non-ciliated cells called club cells. [6]
There are three major types of alveolar cell. Two types are pneumocytes or pneumonocytes known as type I and type II cells found in the alveolar wall, and a large phagocytic cell known as an alveolar macrophage that moves about in the lumens of the alveoli, and in the connective tissue between them. Type I cells, also called type I pneumocytes ...
During inhalation air enters the trachea via the nostrils and mouth, and continues to just beyond the syrinx at which point the trachea branches into two primary bronchi, going to the two lungs (Fig. 16). The primary bronchi enter the lungs to become the intrapulmonary bronchi, which give off a set of parallel branches called ventrobronchi and ...
The respiratory airway secretory cell (RAS), is found in the lungs of humans and some other mammals, notably ferrets. They are facultative progenitors that have important functional roles in maintaining lung airway health. Their role in maintaining the gas-exchange compartment of the lung is critical and they may be altered in chronic lung disease.
The main or primary bronchi enter the lungs at the hilum and initially branch into secondary bronchi also known as lobar bronchi that supply air to each lobe of the lung. The lobar bronchi branch into tertiary bronchi also known as segmental bronchi and these supply air to the further divisions of the lobes known as bronchopulmonary segments .
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.