Summary of Spermatogenisis

By Elmarie Green

Spermatogenisis

(Sperm formation)

Sperm develop in the testes in coiled up

tubes called the seminiferous tubules.

Spermatogonia (sperm stem cells) are

located near the outer wall of the tubules,

the cells divide vigorously and

continuously by mitosis which then forms

primary spermatocytes.

3 million

each day!!

The spermatocytes undergo meiosis =

a process of cell division that reproduces

the number of chromosomes found in

typical body cells (2n) to half that number

(n).

In this process two successive divisions of

the nucleus (meiosis I and meiosis II)

reduce the number of chromosomes from

diploid to haploid.

Meiosis is an essential part of gamete

formation as it ensures the diploid

complement of chromosomes are re-

established at fertilization.

The cells which undergo meiosis I

are defined as primary

spermatocytes.

Each of these cells produce two

secondary spermatocytes.

Each secondary spermatocyte

undergoes meiosis II and produces

two small cells called spermatids.

Results in four haploid spermatids.

Lastly spermiogenesis occurs.

Spermatids differentiate into sperm.

Each spermatid undergoes a

streamlining process as it fashions a

tail and sheds superfluous

cytoplasm.

Takes about

10 weeks in

human

males.

Resulting sperm cell:

Head: Contains the nucleus

(chromatin) and acrosome

(enzymes that enable sperm to

penetrate and enter an egg).

Midpiece: Contains mitochondria

spiraled tightly around the core of

the tail(energy).

Tail: An elaborate flagellum

(whiplike movement that propels

sperm forward).