Why is there no smooth muscle present in the alveolar wall for support?

Answer 1

It is the elasticity that keep alveolus in shape. However if it is deflated , surfactant avoid the alveolus from sticking to each other. Smooth muscle greatly hinder the efficiency of gas exchange as it thicken the diffusion surface.

The alveoli consist of an epithelial layer and extracellular matrix surrounded by capillaries. In some The alveoli consist of an epithelial layer and extracellular matrix surrounded by capillaries. In some alveolar walls there are pores between alveoli called pores of Kohn.

There are three major alveolar cell types in the alveolar wall (pneumocytes):

* Type I (Squamous Alveolar) cells that form the structure of an alveolar wall

* Type II (Great Alveolar) cells that secrete pulmonary surfactant to lower the surface tension of water and allows the membrane to separate, thereby increasing the capability to exchange gases. Surfactant is continuously released by exocytosis. It forms an underlying aqueous protein-containing hypophase and an overlying phospholipid film composed primarily of dipalmitoyl phosphatidylcholine.

* Macrophages that destroy foreign material, such as bacteria.