ANSC 340 Lecture Notes - Lecture 30: Human Chorionic Gonadotropin, Red Blood Cell, Allantois
27 Dec 2016
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After fertilization, 4 major events must occur before embryo attaches to uterus: Development of extraembryonic membrane (environment that will support embryo) Embryo- during organogenesis (organ formation) and pre-implantation (before placenta attaches to endometrium) 2-celled embryo (2 blastomeres) 4- cell 8-cell morula (16-cell) early blastocyst hatching blastocyst. Stages 2, 4, 8 cell are totipotent. Single blastomere can give rise to complete, fully formed individual. Dividing a 4-cell stage embryo into 4 separate zonas will produce 4 embryos. Totipotency ends at 16-cell stage (cell differentiation is too difficult) Cleavage ends with hatching- end of development within zp. Blastocoele fills with fluid, pressure, and embryo outgrows zp. Contraction of blastocyst i. e. stress attachment takes 1-1. 5 weeks. Day 13= maternal recognition: block pgf2alpha production or still produce pgf2alpha but re-route it. Association with endometrium (site of attachment to uterus) Production of fetal hormones (hcg, ecg, progesterone, estrogen)
