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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


6 - 8 Weeks

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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Embryonic Development: 6 to 8 Weeks

Chapter 20   6 Weeks: Motion and Sensation

By 6 weeks the cerebral hemispheres are growing disproportionately faster than other sections of the brain.

The embryo begins to make spontaneous and reflexive movements. Such movement is necessary to promote normal neuromuscular development.

A touch to the mouth area causes the embryo to reflexively withdraw its head.

Chapter 21   The External Ear and Blood Cell Formation

The external ear is beginning to take shape.

By 6 weeks, blood cell formation is underway in the liver where lymphocytes are now present. This type of white blood cell is a key part of the developing immune system.

Chapter 22   The Diaphragm and Intestines

The diaphragm, the primary muscle used in breathing, is largely formed by 6 weeks.

A portion of the intestine now protrudes temporarily into the umbilical cord. This normal process, called physiologic herniation, makes room for other developing organs in the abdomen.

Chapter 23   Hand Plates and Brainwaves

At 6 weeks the hand plates develop a subtle flattening.

Primitive brainwaves have been recorded as early as 6 weeks and 2 days.

Chapter 24   Nipple Formation

Nipples appear along the sides of the trunk shortly before reaching their final location on the front of the chest.

Chapter 25   Limb Development

By 6 1/2 weeks, the elbows are distinct, the fingers are beginning to separate, and hand movement can be seen.

Bone formation, called ossification, begins within the clavicle, or collar bone, and the bones of the upper and lower jaw.

Chapter 26   7 Weeks: Hiccups and Startle Response

Hiccups have been observed by 7 weeks.

Leg movements can now be seen, along with a startle response.

Chapter 27   The Maturing Heart

The 4-chambered heart is largely complete. On average, the heart now beats 167 times per minute.

Electrical activity of the heart recorded at 7 1/2 weeks reveals a wave pattern similar to the adult's.

Chapter 28   Ovaries and Eyes

In females, the ovaries are identifiable by 7 weeks.

By 7 1/2 weeks, the pigmented retina of the eye is easily seen and the eyelids are beginning a period of rapid growth.

Chapter 29   Fingers and Toes

Fingers are separate and toes are joined only at the bases.

The hands can now come together, as can the feet.

Knee joints are also present.
6 - 8 Weeks


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