Changes

===Pimary Sexual Differentiation Phase===

===Pimary Sexual Differentiation Phase===

This phase represents the initial phase of differentiation of reproductive tissues. The male Y chromosome in mammals contains genetic code that results in the production of '''testes-determining factor (TDF)''' which is responsible for causing the gonads to develop into testes. In the female fetus, TDF is not produced as there is no Y chromosome and therefore the gonads develop into ovaries.

This phase represents the initial phase of differentiation of reproductive tissues. The male Y chromosome in mammals contains genetic code that results in the production of '''testes-determining factor (TDF)''' which is responsible for causing the gonads to develop into testes. In the female fetus, TDF is not produced as there is no Y chromosome and therefore the gonads develop into ovaries. As the testes begin to develop under the influence of TDF, the '''Sertoli cells''' within the testes begin to produce '''Anti-Mullerian hormone (AMH)''' and this has two main effects. It causes the '''Leydig cells''' within the testes to develop which are able to produce testosterone and this testosterone begins the development of the male duct system. Under the influence of AMH these Laydig cells also begin to produce '''dihydrotestosterone''' which, per the above explanation, is also a key signalling molecule in reproductive system development resulting in the development of the penis, scrotum and accessory sex glands. The second key effect of AMH is the regression of the paramesonephric duct system. In females, the lack of TDF and AMH allows the paramesonephric ducts to become the oviducts, uterus, cervix and internal parts of the vagina.

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