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The Biology of Prenatal Development


6 - 8 Semanas


THE BIOLOGY OF PRENATAL DEVELOPMENT

.English


 

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Desenvolvimento Embrionário: 6 a 8 Semanas

Capítulo 20   6 Semanas: Movimento e Sensação

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.

Capítulo 21   A Orelha Externa e a Formação de Célula Sanguínea

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.

Capítulo 22   O Diafragma e os Intestinos

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.

Capítulo 23   Placas da Mão e Ondas Cerebrais

At 6 weeks the hand plates develop a subtle flattening.

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

Capítulo 24   Formação do Mamilo

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

Capítulo 25   Desenvolvimento dos Membros

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.

Capítulo 26   7 Semanas: Soluços e Resposta a Susto

Hiccups have been observed by 7 weeks.

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

Capítulo 27   O Coração Desenvolvido

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.

Capítulo 28   Ovários e Olhos

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.

Capítulo 29   Dedos das Mãos e dos Pés

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 Semanas