Alveolar cells: Difference between revisions
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{{Unreferencedsection|date=December 2007}} |
{{Unreferencedsection|date=December 2007}} |
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Two types of |
Two types of '''pneumocytes''' contribute to the maintenance of the [[alveoli]] of the lungs: [[Type I pneumocyte]]s and [[Type II pneumocyte]]s. These cells function to aid in gas exchange, secretion of pulmonary [[surfactant]], and self-regeneration |
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==Type I== |
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Type I pneumocytes are responsible for [[gas exchange]] in the alveoli and cover a majority of the alveolar surface area (>95%). While type I pneumocytes account for most of the surface area, they are approximately half as numerous as type II cells, due to differences in size. Type I pneumocytes are large, thin cells stretched across a large surface area, while type II pneumocytes are smaller cells. |
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Type I pneumocytes are unable to [[mitosis|replicate]] and are susceptible to [[toxin|toxic]] insults. In the event of damage, Type II cells can proliferate and/or differentiate into type I cells to compensate. |
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==Type II== |
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[[Image:Alveolar_type_II_cell.jpg|frame|Alveolar type II cell, the lamellar bodies can be seen leaving the surface of the cell.]] |
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Type II pneumocytes are [[granularity|granular]] and roughly [[cuboidal cell|cuboidal]] in shape. Type II pneumocytes are typically found at the [[Alveolar-capillary barrier|alveolar-septal junction]] and cover a much smaller surface area than type I cells (<5%), but are much more numerous. Type II cells are responsible for the production and secretion of [[surfactant]] ([[dipalmitoylphosphatidylcholine]]), a [[phospholipid]] that reduces the alveolar surface tension. Surfactant phospholipids are stored in Type II pneumocytes in lamellar bodies, which are specialized vesicles. Release of surfactant in lamellar bodies occurs from an infant's first breath onwards. |
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Type II pneumocytes can replicate in the alveoli and will replicate to replace damaged Type I pneumocytes. |
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==See also== |
==See also== |
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* {{BUHistology|13905loa}} |
* {{BUHistology|13905loa}} |
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* [http://www.meddean.luc.edu/lumen/bbs/p/ppi10.html Electron micrograph at luc.edu] |
* [http://www.meddean.luc.edu/lumen/bbs/p/ppi10.html Electron micrograph at luc.edu] |
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{{cell-biology-stub}} |
{{cell-biology-stub}} |
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Revision as of 18:41, 4 December 2008
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Two types of pneumocytes contribute to the maintenance of the alveoli of the lungs: Type I pneumocytes and Type II pneumocytes. These cells function to aid in gas exchange, secretion of pulmonary surfactant, and self-regeneration
See also
External links
- Histology at KUMC resp-resp17
- Histology image: 13905loa – Histology Learning System at Boston University
- Electron micrograph at luc.edu
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