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Um Embrião de 8 Semanas
Capítulo 30 8 Semanas: Desenvolvimento do Cérebro
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| At 8 weeks the brain
is highly complex
and constitutes almost half of
the embryo's total body weight.
Growth continues
at an extraordinary rate.
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Capítulo 31 Característica de Destro e Canhoto
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| By 8 weeks, 75% of embryos
exhibit right-hand dominance.
The remainder
is equally divided
between left-handed dominance
and no preference.
This is the earliest evidence of
right- or left-handed behavior.
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Capítulo 32 Virar
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| Pediatric textbooks describe
the ability to "roll over"
as appearing
10 to 20 weeks after birth.
However, this impressive
coordination
is displayed much earlier
in the low-gravity environment
of the fluid-filled
amniotic sac.
Only the lack
of strength required
to overcome the higher
gravitational force
outside the uterus prevents
newborns from rolling over.
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| The embryo is becoming
more physically active
during this time.
Motions may be slow or rapid,
single or repetitive,
spontaneous or reflexive.
Head rotation, neck extension,
and hand-to-face contact
occur more often.
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| Touching the embryo
elicits squinting,
jaw movement,
grasping motions,
and toe pointing.
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Capítulo 33 Fusão da Pálpebra
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| Between 7 and 8 weeks,
the upper and lower eyelids
rapidly grow over the eyes
and partially fuse together.
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Capítulo 34 Movimento de Respiração e Micção
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| Although there is no air
in the uterus,
the embryo displays intermittent
breathing motions by 8 weeks.
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| By this time,
kidneys produce urine
which is released
into the amniotic fluid.
In male embryos,
the developing testes
begin to produce
and release testosterone.
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Capítulo 35 8 a 9 Meses (32 a 36 Semanas): Formação dos Alvéolos, Segurar com Força, Preferências de Gosto
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| The bones, joints,
muscles, nerves,
and blood vessels
of the limbs
closely resemble
those in adults.
By 8 weeks the epidermis,
or outer skin,
becomes a multi-layered
membrane,
losing much of its transparency.
Eyebrows grow as hair
appears around the mouth.
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Capítulo 36 Resumo das Primeiras 8 Semanas
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| Eight weeks marks the end
of the embryonic period.
During this time,
the human embryo
has grown from a single cell
into the nearly
1 billion cells
which form over 4,000
distinct anatomic structures.
The embryo now possesses
more than 90% of the structures
found in adults.
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