KINS 1224 Chapter Notes - Chapter 29: Zona Pellucida, Acrosome Reaction, Fallopian Tube
27 Apr 2016
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The word embryo is given to an individual 16 days old when it consists of three primary germ layers called the ectoderm, mesoderm and endoderm. The events leading up to that stage are called embryogenesis so the first 16 days after fertilization are called pre-embryonic stage. An egg must be fertilized within 12-24 hours of ovulation. It takes 72 hours for an egg to reach the uterus. In order to fertilize an egg before it dies, sperm must encounter it somewhere in the distal 1/3 of the uterine tube. Sperm are destroyed by vaginal acid or drain out. Others fail to penetrate the mucus of the cervical canal. Approximately 2-3000 spermatozoa reach the vicinity of the egg. Sperm are viable for up to 6 days. Sperm can reach the distal uterine tube within 5-10 min of ejaculation but can"t fertilize the egg for about 10 hours. Sperm undergo capacitation which makes them capable of penetrating an egg.
