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22 Cards in this Set
- Front
- Back
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How many weeks from conception to birth?
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38 weeks
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Prenatal period
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Period between conception and birth and is divided into two periods the embryonic period and fetal period.
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Embryonic period
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first 8 weeks and by the end all major organs are in place and looks somewhat like a human.
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fetal period
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remaining 30 weeks after the embryonic period. The organs grow larger and more complex.
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Skin
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two layers and outer layer called the epidermis and an inner. leathery layer called teh dermis.
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Outer body wall
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mostly trunk muscles. Dorsally it also contains the vertebral column through which the spinal cord runs. Ribs attach to each bondy vertebra in the thoracic region of the trunk wall.
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Body cavity and inner tube
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inner tube is made of the respiratory and digestive structures. Peritoneal cavity lined by visceral and parietal serosae surrounding the digestive tube. The digestive tube has a muscular wall and is lined internally by a sheet of cells. The respiratory structures form the inner tube. The body cavities in the thorax are the pleural vacity around the lungs and the pericardial cavity around the heart.
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kidney and gonads
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kidneys lie directly deep to the dorsal body wall in the lumbar region of the back the gonads originate in a similar posistion and migrate to other parts during the fetal period.
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limbs
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consist mostly of bone muscle and skin
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oocyte
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an immature egg that each month a woman's two ovaries releases. The cell is normally drawn into a uterine tube (fallopian) which provides a way to the uterus (womb).
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conception
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the fertilization of an oocyte with sperm that usually occurs in the lateral third of the uterine tube.
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zygote
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fertilized oocyte
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blastomeres
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as the zygote (fertilized oocyte) moves toward teh uterus it divides these new cells are called blastomeres. Blastomeres are continually getting smaller because there isn't enough time between divisions.
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Cleavage
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the early division sequenece that provides large number of cells needed as building blocks for the embryo.
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morula
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72 hours after fertilization 12-16 blastomeres have developed from cleavage and is called a morula.
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Blastocyst
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During day 4 the late morula which now has about 60 cells enters the uterus and takes up fluid into a central cavity. This new cavity is called a blastocyst.
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Which two cells are present in the blastocyst stage?
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Inner cell mass which is a cluster of cells on one side and a layer of cells surrounding the cavity called teh trophoblast.
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Inner cell mass
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forms the embryo
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trophoblast
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help from the placenta which is the structure that transfers nutrients from teh mother to the fetus.
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How long does the blastocyst stage last?
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3 days from day 4 to 7 during this time teh blastocyst floats freely in cavity of the uterus.
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implantation
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on day 6 of the blastocyst stage the blastocyst starts to burrow into the wall of the uterus and takes about a week to complete. The trophoblast layer erodes inward until the entire blastocyst is embedded in the uterine wall.
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monozygotic twins
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when the inner cell mass of a single blastocyst splits into two during teh early stages of cleavage in week 1 or 2.
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