Library · Cell
Type I pneumocyte
Make it clearer
The alveolus is the little sac where the lung does its work, and what lines it almost completely is the type I pneumocyte: it covers 70% of the inner surface. It is a thin, squamous cell, meaning flattened like a scale.
That thinness is the whole point. On the other side there is a capillary, and the pneumocyte shares a basement membrane with that capillary's endothelium, the layer that lines it from within; the basement membrane is the sheet both of them rest on. The two cells pressed against that sheet form the air-blood barrier, and oxygen gets in and carbon dioxide gets out by crossing it. It is a sheet of tissue paper stretched between air and blood, thin enough for gas to cross.
Thin does not mean leaky. These cells are joined to one another by tight junctions, seals that make the barrier impermeable and limit the entry of fluid into the alveolus.
The alveolus is also home to the type II pneumocyte, which covers barely 7% of the surface.
In brief
The type I pneumocyte covers 70% of the inner surface of each alveolus and is thin and squamous.
It shares a basement membrane with the capillary endothelium, forming the air-blood barrier where gas exchange takes place.
A sheet of tissue paper stretched between air and blood, thin enough for gas to cross.
Its tight junctions create an impermeable barrier that limits fluid entry into the alveolus.
The type II pneumocyte covers 7% of the inner surface of the alveolus.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingHistology, Alveolar Cells, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated