BIO380H5 Lecture Notes - Zona Pellucida, Endometrium, Twin
Document Summary
Lecture 3- life and death in the ovary. In females, primary oocytes are arrested in prophase i until puberty. When the egg gets released during ovulation it is suspended in metaphase ii. When a sperm fertilizes it, the egg completes meiosis ii. In female embryos, mitotic increase of eggs will continue until about 5 months after conception. By the time the baby is born, mitotic increase of eggs is arrested. Primary oocyte is arrested in meiosis i (prophase i) Oogonium primary oocyte enters meiosis i but stops at prophase i till puberty primary oocyte completes meiosis i and enters meiosis ii (only gets up to metaphase ii). It is now a secondary oocyte at puberty, this secondary oocyte is released. If fertilization occurs it will complete meiosis ii. When the sperm penetrates the zona pellucida layer secondary oocyte will complete meiosis ii. At puberty, hormones from the hypothalamus stimulate release of fsh and lh from the pituitary glands.
