Library · Cell
Type II pneumocyte
Make it clearer
The alveolus is one of the many tiny sacs attached to the alveolar ducts. Its wall is not made of a single kind of cell but of three main types: type I pneumocytes, type II pneumocytes, and alveolar macrophages. The macrophages are not the focus of this card. The type I cells are squamous epithelial cells, meaning flattened like scales, and they can cover up to 97 percent of the alveolar surface.
The type II pneumocyte is the one that matters here. It sits tucked between the type I cells, and its job is to make something called pulmonary surfactant, a mixture of phospholipids and proteins. Phospholipids are a kind of fat. What surfactant does is lower the surface tension of the alveolus. Surface tension is the force that tends to pull a soap bubble in on itself, or to draw a drop of water into a little ball. Reducing that force inside a small moist sac is exactly this cell's job.
In brief
The type II pneumocyte is one of the three main cell types in the wall of the alveolus, along with type I cells and alveolar macrophages; the alveolus is one of the many small sacs attached to the alveolar ducts.
It sits between the type I cells and secretes pulmonary surfactant, a substance made of phospholipids and proteins that lowers the surface tension of the alveolus.
Type I cells, by contrast, are squamous epithelial cells that can cover up to 97 percent of the alveolar surface.
Sources (1)
- OpenStax, Rice UniversityAnatomy and Physiology 2e, 22.1 Organs and Structures of the Respiratory SystemPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated