chapter 29 development and inheritance

series of functional changes

corona radiata, zona pellucida

oocyte cell membrane depolarizes so another Sperm cannot fuse

molecules released in the fast block harden the zona pellucida

male and female pronuclei fuse, producing a single diploid nucleus

dizygotic (fraternal) twins- produced from independent release of 2 secondary oocytes and the fertilization of each by different sperm, monozygotic (identical) twins- develop from a single fertilized ovum

progressively smaller cells produced by cleavage

blastomeres/blastocyst

7-8 days

blastocyst

embryoblast- inner cell mass develops into the embryo, trophoblast- nourish embryo (will divide into 2 layers)

decidua basalis- between embryo and stratum basale of uterus and provides glycogen and lipids for developing embryo, decidua capsularis- between embryo and uterine cavity and lines noninvolved areas of uterus grows over embryo, decidua parietalis- remaining modified endometrium that lines the noninvolved areas of the rest of the uterus

syncytiotrophoblast, cytotrophoblast

syncytiotrophoblast

chorion

human chorionic gonadotropin (hCG)

rescues the corpus luteum from degeneration and sustains it’s secretion of progesterone and estrogen

hypoblast (endoderm), epiblast (ectoderm)

bilaminar embryonic disc

epiblast

yolk sac

syncytiotrophoblast

2 layers of trophoblast

bilaminar embryonic disc becomes connected to trophoblast

embryonic development where the three primary germ layers form

endoderm- as cells invaginate inward some of them displace the hypoblast, ectoderm- cells remaining in the epiblast, mesoderm- cells that remain between epiblast and endoderm

allantois, yolk sac, chorion, amnion

grows out of digestive system; forms into part of umbilical cord

formation of primordial germ and blood cells

outermost membrane; forms part of placenta; secretes hCG hormone; suppress mothers immune system