human development 10 12

human development 10 12 - Periods of prenantal development:...

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Periods of prenantal development: Germinal period (approx 2 weeks) see table 4.1 in text on pg. 41 Organism usually arrives in uterus on about the 4 th day post conception implantation usually occurs by 10 th day post conception Embyonic period (2 to 8 weeks) Implantation for point at which all systems are formed Blastocyst( inner mass of cells) : Endoderm-respratory system: lungs Digestive system:pharnx,stomach,intestines. Mesoderm- Circulatory system heart blood lymph Skeleton: bone,cartilage,muscles and connecting tissues Excretory system:kidneys Reproductive system Inner layer of skin (dermis) Outer layers of digestive tube Trophoblasts(outer mass of cells): support systems Placenta Umbilical cord-two ateries,one vein Amnion-bag of fluid in which embroys floats Controls temp.and humidity provides cushion Fetal period (9 weeks to birth) “ripening” of fetus Age of viability-23-25 weeks post conception Lanugo
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Vernix Teratogens/teratology: Thalidomide Some homoones found in birth contol pills
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human development 10 12 - Periods of prenantal development:...

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