reproduction in humans formation of gametes a spermatogenesis b oogenesis
TRANSCRIPT
![Page 1: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/1.jpg)
REPRODUCTION IN HUMANS
Formation of gametes
A Spermatogenesis
B Oogenesis
![Page 2: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/2.jpg)
SPERMATOGENESIS
Production of spermBegins between ages
of 11 to 15 and continues until death
100 to 200 million sperm are made a day
![Page 3: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/3.jpg)
SPERMATOGENESIS
Each seminiferous tubule is surrounded by a layer of epithelium on which sit spermatogonia
These divide by mitosis to form dipolid cells
Some of these cells move towards the middle of the tubule becoming primary spermatocytes
![Page 4: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/4.jpg)
SPERMATOGENESIS
Primary spermatocytes then divide by meiosis.
After first meiotic division two secondary spermatocytes are formed.
![Page 5: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/5.jpg)
SPERMATOGENESIS
Two or three days later the secondary spermatocytes undergo a second meiotic division to produce haploid spermatids.
![Page 6: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/6.jpg)
SPERMATOGENESIS
The spermatids mature over the next few weeks into spermatozoon.
The whole process takes about 64 days.
![Page 7: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/7.jpg)
![Page 8: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/8.jpg)
SPERMATOGENESIS
At all stages the developing sperm are supported and nourished by much larger non-dividing cells called Sertoli cells or nurse cells.
The fully developed sperm are carried by a fluid released by the Sertoli cells.
![Page 9: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/9.jpg)
OOGENESIS
Each ovary weighs about 15g and contains many eggs at different stages of development.
The process begins when a girl is still an embryo
![Page 10: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/10.jpg)
Removing an ovarian cyst!
![Page 11: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/11.jpg)
OOGENESIS
5 or 6 weeks after zygote forms some cells in embryo ovary undergo mitosis to produce diploid oogonia
By 24 weeks the embryo contains millions of oogonia
From then until 6 weeks after birth the oogonia undergo a first meiotic division to form primary oocytes.
![Page 12: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/12.jpg)
OOGENESIS
They remain half way through this division for many years.
Most of the primary oocytes disappear – by puberty about 400 000 remain.
![Page 13: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/13.jpg)
OOGENESIS
As development recommences some of the surrounding ovary cells form the primordial follicle which later develops into the primary follicle
![Page 14: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/14.jpg)
OOGENESIS
At puberty hormones stimulate the primary follicle to become a secondary follicle
One of these will develop each 28 days into an ovarian follicle containing the developing primary oocyte
![Page 15: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/15.jpg)
OOGENESIS
The meiotic division commenced as an embryo now completes.
This results in a large secondary oocyte and a tiny polar body
![Page 16: REPRODUCTION IN HUMANS Formation of gametes A Spermatogenesis B Oogenesis](https://reader030.vdocument.in/reader030/viewer/2022032612/56649ec05503460f94bcbe07/html5/thumbnails/16.jpg)
OOGENESIS
It is at this stage that the oocyte is released at the moment of ovulation.
The meiotic division does not actually complete until after the sperm has entered it.