The Reproductive System

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The Reproductive System

The reproductive system occurs in both male and female.

Like in plants it is the male gamete that needs to be transferred to

the female gamete. The female gamete is fertilised and develops inside

the mother’s body so the reproductive systems of both males and

females are highly adapted for this.

Production of sperm is called spermatogenesis.

It occurs at puberty and for the rest of there life.

It takes place in the gonads of the male - the testes. Over 100

million can be made in one day!

Each testis is composed of numerous tiny tubes called seminiferous

tubules. It is in the walls of these tubules that sperm production

actually takes place.

Development begins in the outer side of the wall in a layer of cells

called the germinal epithelium. As the immature sperm cells become

more mature they move to the inner side and break way into the lumen

of the tubule to be carried away to the epididymis for storage. The

process of this production is shown in the next two diagrams.

In between the tubules, inside the testes, are interstitial cells

called Leydig cells. These secrete the hormone testosterone.

There are also blood vessels in close proximity, delivering nutrients

and carrying away some testosterone to other target cells for the

development and maintenance of secondary sexual characteristics, e.g.

facial and pubic hair, deepening of the voice. The testosterone also

stimulates the cells inside the testis involved in spermatogenesis.

Hormonal control of spermatogenesis

The control centres are the pituitary gland and the hypothalamus in

the brain.

The hypothalamus secretes GnRH ...

... middle of paper ...

...ation.

Then the level of oestrogen rises which actually stimulates the

release of LH and FSH.

A surge of LH: this causes ovulation and the development of the corpus

luteum. LH feeds back to inhibit oestrogen release so, as a result,

the levels of LH and FSH begin to fall.

The corpus luteum secretes progesterone: this stimulates the

thickening and the vascularisation of the uterus wall in preparation

for pregnancy...

A) If no pregnancy occurs: the corpus luteum degenerates, progesterone

is no longer released and the lining of the uterus breaks down. The

discharge of the wall is called menstruation. FSH release is no longer

inhibited so the cycle can begin again and a new follicle can develop

b) If pregnancy occurs: the corpus luteum persists due to a hormone (CG

- chorionic gonadotrophin) being released.

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