Term
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Definition
results in progressively smaller cells (inc ratio of nuclear-to-cytoplasm & surface-to-volume ratio of each cell which improves gas exchange)
• As cell division continues solid ball of cells called morula forms
• Blastulation occurs when morula develops cavity called blastocoel
• By fourth day becomes hollow sphere of cells called blastula
• on 6th day, blastocyst (AKA blastula) begins implantation into the uteral endometrium
• little increase in size occurs during gastrulation |
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Term
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Definition
single cell layer of blastula transforms into three-layered gastrula
• Ectoderm – Nervous system, integument (epidermis & hair / epithelium of nose, mouth, anal canal), lens of eye, retina, teeth, neural tube
• Mesoderm – musculoskeletal, circulatory system, excretory system, gonads, connective tissue, portions of digestive & respiratory, notochord
• Endoderm – epithelial lining of digestive & respiratory, parts of liver, pancreas, thyroid, and bladder lining |
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Term
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Definition
| process in an embryo in which one tissue causes another to differentiate |
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Term
| Embryonic Membrane (Eggs) |
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Definition
| Chorion (moist membrane =>** gas exchange), Allantois (sac-like involved in respiration and excretion/ blood vessels for transport), Amnion (amniotic fluid) |
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Term
| chorionic gonadotropin hormone |
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Definition
| secreted by the chorion (when it becomes part of the placenta) and helps maintain the Corpus Luteum (which secretes progesterone to maintain uterine lining) |
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Term
| Placental Internal Development |
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Definition
growing fetus receives oxygen directly from mother through specialized circulatory system (supplies O2 + nutrients / removes CO2 and wastes)
• Placenta and umbilical cord are outgrowths of the four extra-embryonic membranes – amnion, chorion, allantois, yolk sac |
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Term
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Definition
| cervix thins out and dilates, amniotic sac ruptures, rapid contractions followed by birth, then uterus expels umbilical cord and placenta |
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