Gametogenesis and fertilization
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This document discusses gametogenesis and fertilization. It describes the processes of spermatogenesis in males, where spermatogonia undergo meiosis and spermiogenesis over 64 days to form sperm. It also describes oogenesis in females, where ova undergo meiosis to form secondary oocytes. Fertilization occurs when a sperm unites with an oocyte in the uterine tubes, restoring the diploid chromosome number. The results of fertilization include determining embryonic sex and stimulating completion of meiosis.
Gametogenesis and fertilization
- 1. Gametogenesis and fertilization By Dr. Ansari Chairperson & Prof. Anatomy RAKCODS. RAKMHSU (for BDS students) 12/18/2014 1
- 2. The learning outcomes are ? The students are able to chart out the steps in Gametogenesis occurring in male persons and steps of oogenesis occurring in female subjects. ? The result of spermatogenesis and spermiognenesis. ? The result of oogenesis. ? The fertilization is the result of union between the male and female gametes occurring in the female reproductive organs. 12/18/2014 2
- 3. Formation of male gametes is called spermatogenesis ? It occurs in the testis of an adult male. ? The mother cells are called as spermatogonia. ? Each spermatogonium consists of 2n number of chromosomes. ? In human it is 46 chromosomes (22autosomes and XX/XY sexosomes). ? The supporting cells are called as sertoli cells. ? They help in providing nutrition and helps in spermiognenesis-maturation of sperms. 12/18/2014 3
- 4. There are three steps in spermatogenesis ? 1) Meiosis I, during which the number of chromosomes in the cell is reduced to half or 23 chromosomes each; ? 2) Meiosis II, during which each haploid cell forms spermatids; and ? 3) Spermiogenesis, during which each spermatid develops into a sperm cell with a head and tail. ? The entire process of spermatogenesis takes about 64 days. 12/18/2014 4
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- 6. The spermiogensis is regulated by Sertoli cells 12/18/2014 6
- 7. The oogenesis occur in female reproductive organ- ovary 12/18/2014 7
- 8. The fertilization is the union of male and female gametes-it occurs in uterine tubes 12/18/2014 8
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- 10. The result of fertilization ? Stimulates the secondary oocyte to complete meiosis. ? Restores the normal diploid number of chromosomes (46). ? Results in variation of human species as maternal and paternal chromosomes intermingle. ? The embryo contains only maternal mitochondria because the sperm mitochondria are dispersed into the egg cytoplasm and discarded. ? Determines the sex of the embryo. ? The sex chromosome (Y or X) carried by the successful sperm determines embryonic sex. ? The sperm can only survive 48 hours within the female genital tract. 12/18/2014 10
- 11. Monozygotic twin ? A fertilized, single egg splits into two developing zygotes at a very early stage. ? Identical twins; same sex. 12/18/2014 11
- 12. Dizygotic twin:- ? Result from the fertilization by two sperms & two separate ova that have reached maturation at the same time. ? Not identical twins; can be different sexes ? Incidence increases with age of the mother 12/18/2014 12
- 13. Conjoint twins- Siamese twins ? Conjoint twins will result when the germ disk duplicates itself and will not get separated out at a particular point and remain joined. ? Whole two individuals will develop with parts attached with each other. ? Here it is a craniopagus. 12/18/2014 13
- 14. References ? http://education- portal.com/academy/lesson/oogenesis-how- the-female-reproductive-system-produces- eggs.html#lesson ? http://www.youtube.com/watch?v=BFrVmDg h4v4 ? http://www.tutorsglobe.com/getanswer/proc ess-of-fertilization-in-human-beings- 908778.aspx 12/18/2014 14