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National Geographic Society This program is distributed in the U.S. and Canada by National Geographic and EHD. [learn more]

Multilingual Illustrated DVD [Tutorial]

The Biology of Prenatal Development



Introducing the Multilingual Illustrated DVD
Explore the fascinating imagery and facts presented in The Biology of Prenatal Development at your own pace. Each clip from the program is accompanied by its corresponding written script. Select Play Movie to watch any clip. Select See Snapshots to view high resolution images. See the program script and subtitles in 88 languages by using the Choose Language drop-down menu and clicking Refresh. Subtitles are displayed in your chosen language and may be turned on and off by clicking the button found in the lower right corner of the movie player. A "full screen" option is also available by clicking the button.


 
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Chapter 41   4 to 5 Months (16 to 20 Weeks): Stress Response, Vernix Caseosa, Circadian Rhythms

By 16 weeks, procedures involving the insertion of a needle into the abdomen of the fetus trigger a hormonal stress response releasing noradrenaline, or norepinephrine, into the bloodstream.

In the respiratory system, the bronchial tree is now nearly complete.

A protective white substance, called vernix caseosa, now covers the fetus. Vernix protects the skin from the irritating effects of amniotic fluid.

From 19 weeks fetal movement, breathing activity, and heart rate begin to follow daily cycles called circadian rhythms.

Chapter 42   5 to 6 Months (20 to 24 Weeks): Responds to Sound; Hair and Skin; Age of Viability

By 20 weeks the cochlea, which is the organ of hearing, has reached adult size within the fully developed inner ear. From now on, the fetus will respond to a growing range of sounds.

Hair begins to grow on the scalp.

All skin layers and structures are present, including hair follicles and glands.

By 21 to 22 weeks after fertilization, the lungs gain some ability to breathe air. This is considered the age of viability because survival outside the womb becomes possible for some fetuses.


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