Gametogenesis

Gametogenesis

Spermatogenesis refers to the process by which spermatozoa are produced from the germinal epithelium of the testis

Oogenesis is the process where ova is produced from germinal epithelium of the ovaries

Spermatogonia (2n) in germinal epithelium of seminiferous tubules

Mitosis

Primary spermatocytes (2n)

Meiosis (first division)

Secondary spermatocytes (n)

Meiosis (second division)

Spermatids (n)

sperm cells/spermatozoa

SpermatogenesisAt puberty, the germinal epithelial cells

lining the seminiferous tubules start to produce sperms/spermatozoa by meiosis

Each germinal epithelium is diploid and in humans the diploid number is 46

Since the sperm is produced by meiosis, each one will be haploid with 22 single chromosome and X or Y chromosome

SpermatogenesisThe process is as follows:Cells of germinal epithelium become

actively dividing cells called spermatogonia

Each spermatogonium, which is diploid (2n), enlarges to become a primary spermatocyte (also 2n)

SpermatogenesisPrimary spermatocyte undergoes the

first meiotic division forming 2 haploid secondary spermatocytes

Each secondary spermatocyte undergoes the second meiotic division to produce 2 spermatids

Each spermatid matures to form a spermatozoan

Each spermatozoan is made up of a head, a middle-piece and a tail

SpermSperm Microscopic cells produced by the Microscopic cells produced by the

male's testicles which can fertilize male's testicles which can fertilize the female's ovumthe female's ovum. .

They are tiny, living cells 100 times They are tiny, living cells 100 times smaller than a pencil dot. (the smaller than a pencil dot. (the smallest cell in a man’s body smallest cell in a man’s body

Enough sperm would fit on the head Enough sperm would fit on the head of a pin to re-populate the earth if of a pin to re-populate the earth if each sperm fertilized an egg. each sperm fertilized an egg.

It is destroyed by warm body It is destroyed by warm body temperature, acidic environment. temperature, acidic environment.

It can survive in a women’s body for It can survive in a women’s body for 5-8 days. 5-8 days.

Any sperm not ejaculated are Any sperm not ejaculated are passed in the urine.passed in the urine.

Oogenesis

Oogonia (2n) in germinal epithelium of seminiferous tubules

Mitosis

Primary oocytes (2n)

Meiosis (first division)

Secondary oocyte (n)

Meiosis (second division)

ootid (n)

ovum

Ova Ova

The female reproductive The female reproductive cell. cell.

They are the largest cells They are the largest cells in the female body. in the female body. (about (about the size of a grain of sand.) the size of a grain of sand.)

The female baby is born The female baby is born with all the ova she will with all the ova she will ever have ever have (about 200,000 in each (about 200,000 in each ovary). ovary).

About 400-500 ova About 400-500 ova mature and are released mature and are released over a lifetime over a lifetime