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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]
A pulmonary alveolus (pl.: alveoli, from Latin alveolus, "little cavity"), also known as 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 epithelial lining of the upper respiratory tract is interspersed with goblet cells that secrete a protective mucus. This helps to filter waste, which is eventually either swallowed into the highly acidic stomach environment or expelled via spitting. The epithelium lining the respiratory tract is covered in small hairs called cilia.
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 columnar epithelium along with some non-ciliated cells called club cells. [6]
The primary purpose of the respiratory system is the equalizing of the partial pressures of the respiratory gases in the alveolar air with those in the pulmonary capillary blood (Fig. 11). This process occurs by simple diffusion , [ 22 ] across a very thin membrane (known as the blood–air barrier ), which forms the walls of the pulmonary ...
Club cells, also known as bronchiolar exocrine cells, [1] are low columnar/cuboidal cells with short microvilli, found in the small airways (bronchioles) of the lungs. [2] They were formerly known as Clara cells. Club cells are found in the ciliated simple epithelium. These cells may secrete glycosaminoglycans to protect the bronchiole lining.
The bronchi are conducting passages for air into the lungs. A bronchus (/ ˈbrɒŋkəs / BRONG-kəs; pl.: bronchi, / ˈbrɒŋkaɪ / BRONG-ky) is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi to branch from the trachea at the carina are the right main bronchus and the left main ...
Pulmonary neuroendocrine cells are found throughout the respiratory epithelium including the alveolar epithelium, [24] though they only account for around 0.5 percent of the total epithelial population. [25] PNECs are innervated airway epithelial cells that are particularly focused at airway junction points. [25]