Early Embryology Simple Summary
Embryology
Week 1
Ovarian cycle:
GnRH from hypothalamus FSH and LH from pituitary cyclic changes in the ovary.
Follicular phase: * 15-20 preantral follicles start to grow due to FSH * 1 reaches full maturity released * Others undrgo atresia * Estrogens are released which; 1. Proliferate endometrium 2. Thin the cervical mucus 3. Stimulate pituitary to release LH * The LH; 1. Elevate concentrations of maturation promoting factor (oocytes complete meiosis one and begin meiosis II, stopped at metaphase) 2. Stimulate progesterone production by follicular stromal cells (luteinisation) 3. Cause follicular rupture
Ovulation
* High concentration of LH makes the collagenase active breaks down collagen by bulging follicle rupture. * Oocyte + cumulus oophorus breaks free ovulation.
Luteal Phase: * After ovulation, under influence of LH, theca and granulose cells become lutein cells. * Corpus luteum secretes progesterone. * Eventually (~10 days after ovulation), corpus albicans is formed. (if no fertilization!) * If fertilised, syncitiotrophoblasts release hCG
Transport * Swept in by fimbria of the oviduct and cilia. * Once in tube, cumulus cells withdraw their cytplasmic processes from the zona pellucida and lose contact with the oocyte.
Fertilisation
* Sperm must undergo (a) capacitation (glycoprotein coat and seminal plasma proteins removed) * (b) Acrosome reaction- after bind to zona pellucid, acrosome releases proteins needed to bind. * Fusion of gametes oocyte membrane becomes impenetrable to other sperm, zona pellucid alter structure to prevent further binding. * Meiosis II is completed when sperm enters.
Blastocyst formation * 2 cell stage 4 cell 8 cell 16 cell (morula) * Morula has inner cell mass (make embryo) and outer cell mass (trophoblast i.e. placenta) * ~ when morula enters uterus, fluid penetrates zona
Week 1
Ovarian cycle:
GnRH from hypothalamus FSH and LH from pituitary cyclic changes in the ovary.
Follicular phase: * 15-20 preantral follicles start to grow due to FSH * 1 reaches full maturity released * Others undrgo atresia * Estrogens are released which; 1. Proliferate endometrium 2. Thin the cervical mucus 3. Stimulate pituitary to release LH * The LH; 1. Elevate concentrations of maturation promoting factor (oocytes complete meiosis one and begin meiosis II, stopped at metaphase) 2. Stimulate progesterone production by follicular stromal cells (luteinisation) 3. Cause follicular rupture
Ovulation
* High concentration of LH makes the collagenase active breaks down collagen by bulging follicle rupture. * Oocyte + cumulus oophorus breaks free ovulation.
Luteal Phase: * After ovulation, under influence of LH, theca and granulose cells become lutein cells. * Corpus luteum secretes progesterone. * Eventually (~10 days after ovulation), corpus albicans is formed. (if no fertilization!) * If fertilised, syncitiotrophoblasts release hCG
Transport * Swept in by fimbria of the oviduct and cilia. * Once in tube, cumulus cells withdraw their cytplasmic processes from the zona pellucida and lose contact with the oocyte.
Fertilisation
* Sperm must undergo (a) capacitation (glycoprotein coat and seminal plasma proteins removed) * (b) Acrosome reaction- after bind to zona pellucid, acrosome releases proteins needed to bind. * Fusion of gametes oocyte membrane becomes impenetrable to other sperm, zona pellucid alter structure to prevent further binding. * Meiosis II is completed when sperm enters.
Blastocyst formation * 2 cell stage 4 cell 8 cell 16 cell (morula) * Morula has inner cell mass (make embryo) and outer cell mass (trophoblast i.e. placenta) * ~ when morula enters uterus, fluid penetrates zona