Download HUMAN DEVELOPMENT

HUMAN DEVELOPMENT
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EARLY DEVELOPMENT
Cleavages: mitotic cell divisions of the zygote
Morula: solid ball of about 50 cells of an embryo
Blastocyst: fluid-filled cavity in the center of the morula, transformed into a
hallow structure.
Implantation: 6-7 days after fertilization the blastocyst attaches to the wall of
the uterus.
Gastrulation: Process of cell migration where two layers split into three
Ectoderm, mesoderm, and endoderm: Forms all tissues and organs fig. 43-9
Amnion & Chorion:2 membranes that surround, protect, and nourish embryos
By end of 3rd week, nervous system starts to form; primitive digestive system
Placenta: Vital connection between mother and baby, was the chorion
Supplies nutrients and oxygen & eliminates CO2 & metabolic wastes
Blood supplies of mother and baby do not mix, they flow past each other
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HUMAN DEVELOPMENT
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Fetus: after 8 weeks of development
After three months most organs are developed as well as the umbilical cord
which connects the the fetus to the placenta
Muscular system developed, some movement 9cm long 15 grams
amniotic sac develops which cushions and protects the fetus
LATER DEVELOPMENT
Fourth, fifth, and sixth months:
tissues become more complex and specialized
skeletal systems forms, strong heartbeat, 35 cm and 700 g
CHILDBIRTH
After about 9 months, oxytocin is released and stimulates muscle
contractions called LABOR to increase cervix to 10 cm.
contractions become more powerful and frequent, amniotic sac ruptures,
baby is forced out of uterus and vagina attached to umbilical cord.
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AFTER CHILDBIRTH
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Prolactin: Pituitary hormone stimulating production of mild in breast tissue
Stimulation of nerve cells in the breast transmits impulse to the hypothalamus.
Pituitary releases 10x more prolactin than normal.