Recap of Oogenesis and Spermatogenesis
When in the fetus, germ cells divide by mitosis and spread into the ovary's cortex
At 4 months, the cells grow divide by meiosis. This is the first meiosis division
At 7 months, follicle cells form around the cells, which are still undergoing the 1st meiosis division
During the menstrual cycle, primary follicles begin to develop and the oocyte completes the 1st meiosis devision.
In a secondary follicle, the follicles multiply and a fluid-filled cavity is created. Now the oocyte begins the second meiosis division
The diploid germinal epithelium cells divide by mitosis to make more diploid cells.
These diploid cells get bigger and are now called primary spermatocytes. This is cell growth.
Each primary spermatocyte experiences the first division of meiosis and make two secondary spermatocytes.
Each secondary spermatocyte experiences the second division of meiosis and makes two haploid spermatids.
The spermatids attach to the nurse cells that help them edvelop into spermatozoa. This is cell differentiation.
Sperm detach from nurse cells and are carried out of the testis by fluid in the seminiferous tubule.
The products of Oogenesis
Egg has to be able to provide for the start of the growth and development of an early embryo.
The egg is much larger than the sperm cell due to it's 2 meiosis divisions, creating a larger egg and a smaller "polar body" that dies each time. This means it has a large cytoplasm.
Eggs are only formed about once once per menstrual cycle
The products of Spermatogenesis
Sperm must have haploid nucleus, falagellum, and a method of entering the egg.
For each meiosis 4 spermatids are produced, so they are much smaller than the eggs and have less cytoplasm.
Sperm are produced constantly by testes after puberty, and there are approx. 1 million present at any time.
Drafted by Venetia (Biology)