Alveoli

What are alveoli?

Air-filled pockets within the lungs where all gas exchange takes place

What is the relationship between alveoli and the capillary bed that surrounds them?

There is a very close relationship as there is a small diffusion distance and large SA to volume ratio

What is the structure of an aleolus like?

• Has an extensive network of capillaries

• Is surrounded by elastic fibres

• Fibres recoil during exhalation which reduces size of alveoli and push air out of lungs

• For gas to exchange efficiently: alveoli walls must be very thin (<1um) and the surface area must be vast (about 35 times the surface area of the body)

What do alveoli in a pulmonary lobule look like?

What does alveolar epithelium consist of?

• Simple squamous epithelium

• Thin, delicate Type I cells

What is alveolar epithelium patrolled by?

Alveolar macrophages (also called dust cells)

What does alveolar epithelium contain?

Septal cells (Type II cells) that produce surfactant