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40 Cards in this Set
- Front
- Back
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Cleavage
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series of rapid cell divisions in which large fertilized egg divides into about 50 smaller ones that do not grow
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how many days does it take for the fertilized egg to move into uterus from oviduct
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5 days
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morula
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the ball of cells by day 3
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blastocyst
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by day 5-6 , fluid-filled cavity is formed and differentiated into two types of cells: inner cell mass and trophoblast
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inner cell mass
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forms embryo
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trophoblast
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preplacenta cells
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zona pellucida
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remains during cleavage and has the following functions:
1. barrier to sperm entry and prevents mult fertilizations 2. prevents premature implantation 3. keeps blastomere cells together 4. prevents immune attacks as it has no antigens on surface 5. allows nutrients to reach embryo EVENTUALLY blastomere secretes enzymes to hatch out of zona |
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fate of invasive cells
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proliferate to eventually surround embryo; secretes enzymes that digest hole in endometirium to allow embrtyo to move through outer lining of endometrium and into inner layer' secretes progesterone and estrogen
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fate of noninvasive cells
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will form extraembryonic membranes? secrete HCG to maintain corpus luteum
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how long does it take to move through outer lining endo to inner layer
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five days
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ectopic implantation
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most common type is tubal 1/80
causes are unclear often associated with PID |
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Molar pregnancy; Hydatidiform Mole
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1:1000; when all chromosomes are male thus only placental tissues and secretion of HCG but no embryo
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invasive placenta
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outer part of preplacenta grows as one giant cell membrane with many nuclei; erodes endome and forms thin layer at interface btween embryonic and maternal tissue of placenta
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none-invasive placenta
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forms cellular part of placenta; fetal blood vessels grow into it to form exchange organ of placenta
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amnion
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new caivty develops over inner cell mass and become lined with new cells; this new tissue is amnion; will enlarge to completely surround embryo to immerse support fluid
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yolk sac
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blastocyst cavity bellow inner cell mass become lined with new cells' new tissue is yolk sac; evolutionary vestige of nutritional organ; initially ocntinuous with future gut
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gastrulation
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cell movement where some upper cells migrate down between uppermost cells and lowermost cells to form mesoderm; uppermost cells which remain behind are ectoderm; lowermost cells are endoderm
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primitive streak
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site at which upper cells dive down; seen as temp long narrow crevice in the upper surface that marks front-back axis; begins at back, elongate to front and regresses to back; organizes embryonic axis
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inner cells mass are embryonic stem cells:
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pluripotent meaning can make all tissue and can also divide indefinitely
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ectoderm
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skin, nervous system
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mesoderm
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muscle, bone, outer parts of organs, outer part gut
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endoderm
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gut lining, lining organs
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axial organization
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as germ layers are made head and tail are determined as well as in and out
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notochord
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rod like structure that forms from mesoderm in front of regressing primitive streak; positioned just below future vertebrae and dives support; alter disappears
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neural tube
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ectoderm along midline folds and forms tube which drops down into mesoderm separately; anterior end of tube is large and will form head whereas the rest of tube will be spinal cord
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somites
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mesoderm along each side of neural tube condenses into series of pairs of cubes; form front to back to make about 40 pairs; will form vertebrae and ribs
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body cavity
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mesoderm splits apart forming internal cavity; cavity enlarges to become body cavity for internal organs; mesoderm surrounds organs
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external body
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body folds, flat embryo rolls up into a tube with ectoderm on outside, and endoderm inside, head and tail folds form large head and small posterior; embryo has body shape in about 4 weeks
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gut
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body folds encloses endoderm into tube; part of yolk sac included; endoderm becomes lining of gut and will also become lining of some internal organs
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Twinning
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30/1000; 90% frat 10% identical
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Fraternal
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originates from 2 ovulated eggs; genetically different with separate amnion and placental
2 placentas but can merge; membranes still separate |
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identical
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originates from 1 fertilized egg and is genetically identical
a. complete split of cleaving embryo b. 2 innercell masses form c. 2 primitive streaks 1 placenta; other membranes close together or merged; one amnion can happen |
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D of nervous system
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anterior of neural tube develops several large expansions for head; posterior stays smooth and small to become spinal cord
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D of vertebrae
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somites formed from mesoderm wrap around neural tube ; also extend a tongue away from neural tube to become ribs
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D of face and mouth
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pharyngeal bars appear at front of head; bumps enlarge, change shape, and join together to cover mouth and give rise to jaws, nose, lips, forehead
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circulatory system
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mesoderm just below head at belly side condenses into a large tube which begins to pump blood; mesoderm elsewhere forms smaller tube for blood vessels;
ones of the first organs to form because imperative heart folds and divides into four chambers |
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urogential system
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mesoderm in middle back form ridges protruding into body cavity; these form kidney and genital system
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digestive organs and lungs
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endoderm becomes surrounded by mesoderm and develop together; endoderm becomes lining and glands; mesoderm becomes muscles and support cells; esophagus, stomach, intestines form by differential elongation; liver, lungs, pancreas from from small protrusion of endoderm which then repeatedly branch
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limbs
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form from mesoderm and ectoderm
toes form last |
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period of fetal development
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9 weeks to birth; 50 mm long and 8 grams to 360 long to 3400 grams
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