Biology Forums - Study Force

What encases/surrounds the alveoli, or what are the lobes made of that encase the alveoli and bronchi? Are they smooth muscle that expands during inspiration?

There no smooth muscle present in the alveolar wall. 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.

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.

Hi Padre,

Based on the pictures online, it shows a lung with a tree like branches that imbed into the lung. The tree like branches are the alveolar cells/walls and bronchi. However, in the picture there seems to be pink stuff enshrouding the tree of alveolar and bronchi, and that looks like different cells unrelated to the alveolar. Also, the  visceral pleura seems to be attached to something other than the alveolar?

Is the whole entire lung just really entirely composed of type 1 and type II alveolar cells? 

No, the lungs are composed of various specialized cells and tissues.

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Thanks Padre and Doubleu for your help! I see the picture better now!