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Desenvolvimento Embrionário: 6 a 8 Semanas
Capítulo 20 6 Semanas: Movimento e Sensação
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| 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.
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| A touch to the mouth area
causes the embryo
to reflexively withdraw
its head.
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Capítulo 21 A Orelha Externa e a Formação de Célula Sanguínea
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| The external ear
is beginning to take shape.
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| 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.
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Capítulo 22 O Diafragma e os Intestinos
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| The diaphragm,
the primary muscle
used in breathing,
is largely formed by 6 weeks.
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| 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.
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Capítulo 23 Placas da Mão e Ondas Cerebrais
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| At 6 weeks the hand plates
develop a subtle flattening.
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| Primitive brainwaves have been recorded
as early as 6 weeks and 2 days.
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Capítulo 24 Formação do Mamilo
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| Nipples appear
along the sides of the trunk
shortly before reaching
their final location
on the front of the chest.
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Capítulo 25 Desenvolvimento dos Membros
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| By 6 1/2 weeks,
the elbows are distinct,
the fingers are
beginning to separate,
and hand movement can be seen.
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| Bone formation,
called ossification,
begins within the clavicle,
or collar bone,
and the bones
of the upper and lower jaw.
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Capítulo 26 7 Semanas: Soluços e Resposta a Susto
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| Hiccups have been observed
by 7 weeks.
Leg movements can now be seen,
along with a startle response.
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Capítulo 27 O Coração Desenvolvido
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| 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.
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Capítulo 28 Ovários e Olhos
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| In females, the ovaries
are identifiable by 7 weeks.
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| By 7 1/2 weeks,
the pigmented retina of the eye
is easily seen
and the eyelids
are beginning a period
of rapid growth.
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Capítulo 29 Dedos das Mãos e dos Pés
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| Fingers are separate
and toes are joined
only at the bases.
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| The hands can
now come together,
as can the feet.
Knee joints are also present.
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