Prenatal Form and Function – The Making of an Earth Suit

Unit 17:   7 to 8 Months (28 to 32 Weeks)

  Closer Look: 

  Applying the Science: 

Movie 17.1 - 7 to 8 Months

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Figure 17.1 - 3D Ultrasound

The Biology of Prenatal Development DVD
Copyright © 2006 EHD, Inc. All rights reserved.

Each day, the adrenal glands produce large amounts of steroid products. The adrenal glands have doubled in size since week 20, and will double again before the end of pregnancy.1

Breathing movements become more common, occurring 30 – 40 percent of the time in an average fetus.2

Sleep patterns follow circadian rhythms starting in the 28 week fetus.

Movie 17.2 - Breathing Movements

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Starting at 32 weeks, true alveoli (al-ve’o-li), or air “pocket” cells, begin forming from alveolar ducts. Development of alveoli continues through birth and until about 8 years of age.3

Movie 17.3 - Alveoli Formation

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As this boy reaches his 8th birthday, his lungs will finally have their complete number of alveoli – those important microscopic structures that help our body exchange oxygen and carbon dioxide.