PHSI 208 Lecture Notes - Lecture 57: Gametogenesis, Spermatocyte, Gamete
Document Summary
The testis and ovaries both produce hormones and gametes and share other similarities, but gametes produced are very different. Gametogenesis the production of gametes and are highly motile: continuously produced after reaching reproductive maturity, sperm and testosterone production diminishes w/ age but do not cease. Mitosis begins in utero to increase germ cell numbers. Mitosis and the first stage of meiosis occurs by the fifth month of fetal development: enter first stage of meiosis and become primary oocytes (dna replication) At birth each ovary ~500,000 primary oocytes. First division produces large secondary oocyte and a tiny first polar body (46 chromosomes) The egg begins second meiotic division, polar bodies break down. Ovary releases egg and it does not undergo secondary division until fertilized. Secondary oocyte contains 46 chromosomes but is preparing to undergo division. Once sperm begins to fertilize secondary oocyte it undergoes meiotic division shedding a polar body containing 23 chromosomes.
