Part of Week 1 and All of Week 2 Human Development Flashcards
when does fertilization end?
intermingling of chromosomes at metaphase of zygote’s first mitotic division
how long does fertilization take?
24 hours
first 4 phases of fertilization
1 - sperm capacitated through uterus
2- sperm goes through corona radiate (help from hyaluronidase released from acrosome and tail)
3- sperm penetrates zona pellucida (help from across, esterase, and neuraminidase)
penetration by another sperm now impossible
4- sperm membrane fuses to oocyte membrane, nuclear material enters cell
what part of the sperm does NOT enter the oocyte membrane?
sperm plasma membrane and mitochondria
final phases of fertilization
5- sperm penetrates oocyte membrane, meiosis II completes»_space; mature oocyte + second polar body
6- sperm tail degenerates
7- male and female pronuclei chromosomes replicate»_space;ootid
8- pronuclei of ootid fuse to form zygote
9- chromosomes align on cleavage spinal
10- metabolic activation which causes cleavage
maternal chromosomes decondense and form what?
female pronucleus
nucleus of the sperm enlarges to form what?
male pronucleus
when is meiosis II of the oocyte completed?
when penetration of oocyte occurs
what are the results of fertilization?
- completes meiosis II of oocyte
- restores normal diploid number of chromosomes (46, 2N)
- creates genetic variation
- determines gender
- initiates cleavage of zygote
what is used to stimulate ovarian follicle growth and maturity?
- clomiphene citrate
- gonatotropin
when does cleavage occur?
30 hours after fertilization
what is still surrounded by zona pellucida during cleavage?
blastomeres
what are 12-32 blastomeres called?
morula
when does the morula enter the uterus and blastocyst cavity starts to appear?
4 days after fertilization
blastomere is separated into what 2 parts, because of the fluid?
- trophoblast (placenta, thin outer layer)
- embryoblast (embryo, centrally located)
what do the trophoblast cells secrete?
early pregnancy factor
when will early pregnancy factor appear in mother’s serum?
24-48 hours after fertilization
what can expand when the zona pellucida degenerates after 2 days?
blastocysts
what happens 6 days after fertilization?
- blastocyst attaches to endometrial epithelium
- trophoblasts proliferate
2 layers of trophoblast proliferation
- cytotrophoblast (inner)
- synctiotrophoblast (outer)
which trophoblast layer has a multinucleated mass and no cell boundaries?
synctiotrophoblast
which trophoblast layer produces enzymes to erode maternal tissues so the embryo can burrow into the endometrium?
synctiotrophoblast (end of week 1)
what hormone does the synctiotrophoblast secrete that maintains the hormonal activity of the corpus luteum?
hCG - human chorionic growth hormone
what hormones does the corpus luteum secrete?
estrogen and progesterone
what forms the amnion?
amnioblasts separated from the epiblast
what forms the embryonic disc?
embryoblast
2 layers of the embryonic disc
- epiblast
- hypoblast
which layer of the embryonic disc is thicker columnar cells making the floor of the amniotic cavity?
epiblast
which layer of the embryonic disc is thinner cuboidal cells and forms the primary umbilical vesicle?
hypoblast
what makes up the primary umbilical vesicle?
- hypoblast
- roof of exocoelomic cavity
- exocoelomic membrane
