n. a type of cell that lines the walls separating the air sacs (see alveolus) in the lungs. Type I pneumocytes are flat and inconspicuous. Type II pneumocytes are cuboidal and secrete *surfactant.
Naturally produced in the LUNGS by cells called pneumocytes, this substance is a mixture of phospholipids (see PHOSPHOLIPID) and LIPOPROTEINS. Present in ?uid lining the alveoli (see ALVEOLUS) in the lungs, their action helps maintain their patency. Premature babies may have a de?ciency of surfactant, a disorder which causes severe breathing diffculties – RESPIRATORY DISTRESS SYNDROME or hyaline membrane disease – and HYPOXIA. They will need urgent respiratory support, which includes oxygen and the administration (via an endotracheal tube) of a specially prepared surfactant such as beractant (bovine lung extract) or edfosceril palmitate.... pulmonary surfactant
n. (pl. alveoli) 1. (in the *lung) a blind-ended air sac of microscopic size. About 30 alveoli open out of each alveolar duct, which leads from a respiratory *bronchiole. The alveolar walls, which separate alveoli, contain capillaries. The alveoli are lined by a single layer of *pneumocytes, which thus form a very thin layer between air and blood so that exchange of oxygen and carbon dioxide is normally rapid and complete. Children are born with about 20 million alveoli. The adult number of about 300 million is reached around the age of eight. 2. the part of the upper or lower jawbone that supports the roots of the teeth (see also mandible; maxilla). After tooth extraction it is largely absorbed. 3. the sac of a *racemose gland (see also acinus). 4. any other small cavity, depression, or sac. —alveolar adj.... alveolus
n. a wetting agent. Surfactants can be added to materials used in dentistry to reduce surface tension and so improve flow. Pulmonary surfactant, secreted by type II *pneumocytes, is a complex mixture of compounds (including lipids, protein, and carbohydrates) that prevents the air sacs (alveoli) of the lungs from collapsing by reducing surface tension. In its absence, as in the immature lungs of premature babies, *atelectasis and *respiratory distress syndrome will develop.... surfactant
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