Chemicals & Human Health

Lung Toxicology Problem Set

Problem 4: Lung development

For help to answer the question:

When do the alveoli develop in lungs in humans?
A. during the first 1-2 years of life
B. in the 1-5th week of pregnancy
C. between 3 and 5 years of age
D. during the last 6 weeks of pregnancy
E. continually throughout a person's lifetime


Human lungs are not completely developed at birth. Most of the development of the alveoli occurs after birth. New alveoli form by a process called septation. The existing alveoli grow new septa, or walls, leading to increased surface area. The table below explains the major stages of lung development.

Time of Development Structures that Develop
0-5 week old embryo major airways (trachea, bronchi) form
5-16 week old embryo bronchi branch and subdivide
16-26 week old embryo lung cells differentiate into different cell types
26 week old embryo - birth airways expand and grow
1-2 year old baby alveoli form by the formation of additional septa

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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