Chemicals & Human Health

Lung Toxicology Problem Set

Problem 2: Alveolar structure

For help to answer the question:

Which of the following alveolar cell types clean particles deposited in the lungs?
A. macrophages
B. epithelium type I
C. epithelium type II
D. fibroblasts
E. capillaries


The blind sacs in the lung tissue, called alveoli, consist of several types of cells. Each alveolus has a network of capillaries that carry blood in the lungs.

Epithelium type I cells are the largest, thin cells that form the walls, or septa, of the alveoli. Epithelium type II cells also line the alveoli and secrete a substance called "surfactant." Surfactant coats the alveoli and provides pressure to keep them from collapsing. Without surfactant the alveolar surfaces tend to stick together which causes the alveoli to collapse.

Macrophages in the alveoli are scavenger cells that work to keep the lung free of "foreign" materials. Fibroblasts are part of the connective tissue in the lungs.

Toxicology Problem Set Chemicals & Human Health

The Southwest Environmental Health Sciences Center
The Biology Project
The University of Arizona
Tuesday, October 14, 1997
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