the human life cycle 
Spermatogenesis
Spermatogenesis is the production of the male gametes (reproductive or sex cell) otherwise known as sperm. The production of sperm takes place in the seminiferous tubules within the testes and are formed from cells by a type of cell division called mitosis and then meiosis. This process begins at puberty.
Spermatogonia cells are made by mitotic division of the primordial germ cell. Mitotic cell division produces diploid cells that are identical to the
Parent cell with 46 chromosomes.
The Spermatogonia increases in size and mass and becomes a spermatocyte which then divides by meiosis. Meiotic cell division results in four haploid cells each with 23 homologous chromosome pairs.
Secondary spermatocytes are produced by the first meiotic division.
The second meiotic division produces two spermatids from each secondary spermatocyte.
The spermatids now grow a cytoskeletal structure and the flagellum begins to grow. The flagellum is full of mitochondria which provide energy for motility.
The spermatids DNA is highly condensed and the nucleus becomes surrounded by the Golgi body. The acrosome develops which is full of digestive enzymes that will enable the sperm to penetrate the oocyte.
Mature spermatozoon is produced under the influence of testosterone from the leydig cells in the testes. This hormone also removes unnecessary cytoplasm and organelles. The excess cytoplasm is now consumed by endocytosis from the surrounding sertoli cells in the testes.
The mature spermatozoon is now suspended in the lumen, it will then break away and float down the tube towards the epididymis for storage.
Oogenesis
Oogenesis is the production of the female gametes otherwise known as the Ova or Egg. This process begins in the ovaries before birth. Before Birth
Oogonia are made by mitotic division of the primordial germ cell.
As a result of mitosis from the germinal epithelium the oogonia becomes surrounded by
Spermatogenesis is the production of the male gametes (reproductive or sex cell) otherwise known as sperm. The production of sperm takes place in the seminiferous tubules within the testes and are formed from cells by a type of cell division called mitosis and then meiosis. This process begins at puberty.
Spermatogonia cells are made by mitotic division of the primordial germ cell. Mitotic cell division produces diploid cells that are identical to the
Parent cell with 46 chromosomes.
The Spermatogonia increases in size and mass and becomes a spermatocyte which then divides by meiosis. Meiotic cell division results in four haploid cells each with 23 homologous chromosome pairs.
Secondary spermatocytes are produced by the first meiotic division.
The second meiotic division produces two spermatids from each secondary spermatocyte.
The spermatids now grow a cytoskeletal structure and the flagellum begins to grow. The flagellum is full of mitochondria which provide energy for motility.
The spermatids DNA is highly condensed and the nucleus becomes surrounded by the Golgi body. The acrosome develops which is full of digestive enzymes that will enable the sperm to penetrate the oocyte.
Mature spermatozoon is produced under the influence of testosterone from the leydig cells in the testes. This hormone also removes unnecessary cytoplasm and organelles. The excess cytoplasm is now consumed by endocytosis from the surrounding sertoli cells in the testes.
The mature spermatozoon is now suspended in the lumen, it will then break away and float down the tube towards the epididymis for storage.
Oogenesis
Oogenesis is the production of the female gametes otherwise known as the Ova or Egg. This process begins in the ovaries before birth. Before Birth
Oogonia are made by mitotic division of the primordial germ cell.
As a result of mitosis from the germinal epithelium the oogonia becomes surrounded by
References: Human Biology, Seventh Edition, Sylvia S. Mader www.nhs.uk/livewell/contraception http://www.xtremepapers.com/revision/gcse/biology/characteristics_of_living_organisms.php Class Notes Class Power Points