102-2 - Lecture 2 No more than 3% (babies) have a defunct...

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Lecture 2 No more than 3% (babies) have a defunct NS 75% of aborted babies have CNS or elsewhere @ 10 weeks cerebral hemispheres cerebellum brain stem and spinal cord are formed ( lisinsephalic) @ 16-20 weeks cerebral furrows becomes gyrosephelic as the brain increases in size the gyro and sulci increases The ovary is the size of a pecan Eggs = germ cells 20 millioin sperms per cc First 10 seconds after fertilization the egg becomes impenetrable 32 cell stage = blackberry (murula) @ 8 cell stage occasionally they will fall apart and are capable of independent development (stem cells) Inner cell mass = embryonic disc EMBRYO! 1. Presumptive ectoderm a. Outside surfaces (skin hair central nervous system) 2. Presumptive endoderm a. Linings of the visera 3. Between the endoderm and ectoderm is the presumptive mesoderm which produces the muscle bone and connective tissues as well as forms the notochord (the first sign that the embryo is developing) -Notochord thickens Neural tube = basis of NS
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102-2 - Lecture 2 No more than 3% (babies) have a defunct...

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