Fertilization Flashcards
What phase is a primary oocyte arrested in and for how long? What cells cause this and via what mechanism?
Granulosa cells arrest primary oocyte in Prophase 1. This is held from prenatal until ovulation.
What phase is a secondary oocyte arrested in and for how long? What mechanism causes its release?
Estrogen->LH surge->arrest until Metaphase II until fertilization
What is the role of FSH in ovarian cycle?
Released from pituitary, stimulates granulosa cells making them secrete estrogens. This selects a follicle to reach maturity.
What is the role of LH in ovarian cycle?
Released from pituitary when estrogen threshold reached. Releases primary oocyte from meiotic inhibition and lets it become secondary oocyte (pro 1 to meta 2)
What is source of estrogen and what does it do to endometrium?
Estrogen released from granulosa cells in the follicles. They cause endometrium to grow and trigger LH surge.
ID source of progesterone secretion following ovulation and describe its effect on endometrium.
Progesterone comes from corpus luteum (the ruptured follicle). It arrests endometrium growth and prepares for implantation. Lasts 14 days after ovulation (then menstruation occurs).
What is role of zona pellucida? Of corona radiata?
zona pellucida = membrane between granulosa cells and primary oocyte. contains sperm receptors, stuff for fertilization/post fertilization.
corona radiata = granulosa cells surrounding ZP. accompany mature oocyte and secrete estrogens to stimulate LH surge.
What is capacitation? Acrosome reaction? Cortical reaction?
Capacitation=conditioning of sperm passing thru uterus. Glycoproteins removed and acrosome exposed. 7 hrs long and required for fertilization.
Acrosome rxn=sperm binds zona pellucida, releases enzymes to burrow through.
Cortical rxn=membrane changes release cortical granules; lysosomal enzymes within harden ZP and hydrolyze sperm receptors blocking polyspermy
Lifespan of sperm? Ova? When in menstrual cycle does fertilization occur? Where does it occur?
Sperm: 80 hr
Ova: 24 hr
Fertilization occurs on day of ovulation if sperm deposited earlier, may occur 5 day after sex
Occurs in ampulla (fallopian tube)
What does zona pellucida do after fertilization to help transport and implantation?
Prevents implantation anywhere but endometrium. Blastocyst “hatches” out!!!
What does syncytiotrophoblast do upon implantation?
Burrows in endometrium. Secretes hCG. Corpus luteum then continues progesterone secretion.
What is compaction?
Morula formation creates inner/outer cells, no longer totipotent! only inner cell mass becomes embryo.
How do dizygotic twins form? Monozygotic? Conjoined?
Dizygotic: 2 sperm + 2 eggs
Monozygotic: Embryo splits, inner cell mass splits during “hatching” or early as 2 cell stage
Conjoined: Incomplete embryoblast separation
What’s an ectopic pregnancy? Where do they occur?
Implantation outside of uterus in uterine tube, mostly ampulla though also in abdominal cavity/ovary
If fertilization age is 6 weeks, what is menstrual age?
menstrual age is 8 weeks (two longer than fertilization). Used by clinician. Date since last menstrual period.
