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 hypothalamus secretes GnRH ...
... middle of paper ...
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
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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