Key Terms
Transit time
30 minutes to 2 hours Sperm viability: 3-5 days in uterine tubes Oocyte viability: ~24 hours after ovulation
Definition
Process in the female reproductive tract that prepares sperm for fertilization. What happens: Fluids improve motility AN
Two protective layers surround the oocyte
1. Corona radiata - outer layer of follicular (granulosa) cells 2.
Steps to penetration
1. Capacitated sperm are drawn toward the oocyte by chemical signals from corona radiata cells 2.
Fast block
Near-instant change in sodium ion permeability upon first sperm binding. Depolarizes the plasma membrane.
Slow block (cortical reaction)
Calcium influx triggers cortical granules to fuse with the plasma membrane and release into the space between membrane a
Dizygotic (fraternal) twins
Two eggs released, two sperm fertilize them. Occurs in ~1% of ovulation cycles.
Monozygotic (identical) twins
One zygote splits into two during early development.
Cleavage
Rapid mitotic divisions. Number of cells increases but total volume stays the same.
Syncytiotrophoblast
Trophoblast cells that fuse into a multinucleated body; digests endometrial cells to secure the blastocyst.
Implantation complete
Middle of week 2.
Ectopic pregnancy
Embryo implants outside the uterus.
Placenta previa
Embryo implants near the cervical os; placenta may cover the cervix as it grows. Leading cause of antepartum hemorrhage.
Placenta functions
Nutrition/excretion, gas exchange, endocrine (secretes hCG, estrogens, progesterone).
Neurulation
Ectoderm thickens into neural plate; edges fold up into neural folds; folds converge to form neural tube; tube becomes C