BIOL 1F25 Lecture Notes - Polar Body, Splanchnopleuric Mesenchyme, Somatopleuric Mesenchyme
30 Jan 2013
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Document Summary
Great diagram on p. 4 of notes: gastrulation. Gastrulation is movement of cells from epiblast to inside (begins at 2 weeks) Embryonic axes become apparent, germ layers formed, cell fates are restricted. Epiblast (dorsal side) cells move to streak, through, then spread away. Primitive node moves anteriorly during this process. Fgf8 signaling may be important for this process. Arises from epiblast, hence is most dorsal. Notochord (axial component): regulates development, but disappears later. Paraxial: pinches off into somites, and somites divide into: Dermatome (most dorsal), gives rise to dermis. Myotome, gives rise to skeletal muscle of trunk. Lateral plate mesoderm: two layers due to coelom. Dorsal somatic layer, combines with ectoderm to make somatopleure, gives rise to body wall. Ventral splanchnic layer, combines with endoderm to make splanchnopleure, gives rise to gut, mesenteries, heart, most of circulatory system. Also formed from cells that moved through primitive streak; displaces visceral. Endoderm gives rise to lining of gut, digestive organs, thyroid.
