Difference between revisions of "Internal and External Genitalia Development - Anatomy & Physiology"
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==Introduction== | ==Introduction== | ||
| − | Sexual | + | Sexual differenciaton by default follows a pathways for development of female internal and external genitalia, requiring no active intervention. Endocrine activity of the testes, production of Androgens by Leydig cells and Mullerian Inhibiting hormone by Sertoli cells, is required for sexual differenciation to be diverted down the male genitalia development pathway. |
| − | = Internal | + | = Internal Genetalia = |
| − | |||
* Male: The primitive male reproductive tract '''The Wolffian Duct''' developes from the '''Mesonephric Duct''' | * Male: The primitive male reproductive tract '''The Wolffian Duct''' developes from the '''Mesonephric Duct''' | ||
* Female: The primitive female reproductive tract '''Mullarian Ducts''' develop from the '''Paramesonephric Duct''' | * Female: The primitive female reproductive tract '''Mullarian Ducts''' develop from the '''Paramesonephric Duct''' | ||
| Line 14: | Line 12: | ||
| − | * '''MIH''' from '''Sertoli cells''' and '''Androgens''' from '''Leydig cells''' prevent spontaneous development of female internal | + | * '''MIH''' from '''Sertoli cells''' and '''Androgens''' from '''Leydig cells''' prevent spontaneous development of female internal genetalia. |
| − | * '''Androgens''' actively maintain '''Wolffian Ducts''', which give rise to male internal | + | * '''Androgens''' actively maintain '''Wolffian Ducts''', which give rise to male internal genetalia: |
** Epididymis | ** Epididymis | ||
** Vas Deferens | ** Vas Deferens | ||
** Vesicular Glands/ Seminal Vesicles | ** Vesicular Glands/ Seminal Vesicles | ||
| − | * '''MIH''' causes | + | * '''MIH''' causes Mullarian Ducts to regress |
| + | |||
== Female == | == Female == | ||
| − | * Wolffian Ducts spontaneously regress in | + | * Wolffian Ducts spontaneously regress in absence of Androgens. |
| − | * '''Mullarian Ducts''' persist to give rise to female internal | + | * '''Mullarian Ducts''' persist to give rise to female internal genetalia: |
** Oviducts | ** Oviducts | ||
** Uterus | ** Uterus | ||
** Cervix | ** Cervix | ||
** Cranial Vagina | ** Cranial Vagina | ||
| − | * Normal Ovarian activity is NOT essential for the development of normal female internal | + | * Normal Ovarian activity is NOT essential for the development of normal female internal genetalia. |
---- | ---- | ||
| − | = External | + | = External Genetalia = |
| − | + | ||
== Male == | == Male == | ||
| − | * Potential to develop male | + | * Potential to develop male of female external genetalia. '''Testosterone''' is required to develop male external genetalia. |
* Androgen secretion from the Testes induces: | * Androgen secretion from the Testes induces: | ||
** '''Urethral folds''' to fuse to allow enclosure of the urethral tube. This, together with the cells from the '''genital swelling''', forms the '''shaft of the Penis'''. | ** '''Urethral folds''' to fuse to allow enclosure of the urethral tube. This, together with the cells from the '''genital swelling''', forms the '''shaft of the Penis'''. | ||
** '''Genital swellings''' fuse in the midline to allow formation of the '''Scrotum''' | ** '''Genital swellings''' fuse in the midline to allow formation of the '''Scrotum''' | ||
** '''Genital Tubercle''' expands to give rise to the '''Glans Penis''' | ** '''Genital Tubercle''' expands to give rise to the '''Glans Penis''' | ||
| + | |||
| + | |||
== Female == | == Female == | ||
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| − | * Exposure of the female tract to Androgens will masculinise external | + | * Exposure of the female tract to Androgens will masculinise external genetalia. |
* Failure of proper endocrine communication between the gonads, internal and external genitalia can lead to '''dissociation''' of gonadal and genital sex. | * Failure of proper endocrine communication between the gonads, internal and external genitalia can lead to '''dissociation''' of gonadal and genital sex. | ||
---- | ---- | ||
| − | = | + | = Sexual Differentiation of the Brain = |
| + | |||
| + | |||
| + | == Male == | ||
| + | |||
| + | * '''Testosterone''' secreted into the blood reaches the brain. | ||
| + | * Converted to Dehydrotestosterone and '''Oestradiol''' by Aromatase enzymes in the Hypothalamus. | ||
| + | * Oestradiol masculinises the brain | ||
| + | |||
| + | |||
| + | == Female == | ||
| + | * '''Alpha Fetoprotein''' binds Oestradiol, preventing it from crossing the blood-brain barrier. | ||
| + | * Oestradiol cannot access the Hypothalamus | ||
| + | * Protects female brain from masculising effects of Oestradiol. | ||
| + | ---- | ||
| − | + | = Associated Disorders = | |
| − | |||
| − | * [[ | + | * [[Fertilisation, Implantation and Early Embryonic Development -Turner's Syndrome - Anatomy & Physiology|Turner's Syndrome]] |
| − | * [[ | + | * [[Fertilisation, Implantation and Early Embryonic Development -Kleinfelter's Syndrome - Anatomy & Physiology|Kleinfelter's Syndrome]] |
| − | * [[ | + | * [[Fertilisation, Implantation and Early Embryonic Development -Testicular Feminisation - Anatomy & Physiology|Testicular Feminisation]] |
| − | * [[ | + | * [[Fertilisation, Implantation and Early Embryonic Development -Adrenogenital Syndrome - Anatomy & Physiology|Adrenogenital Syndrome]] |
| − | + | * [[Fertilisation, Implantation and Early Embryonic Development -Intersex - Anatomy & Physiology|Intersex]] | |
| − | |||
| − | [[ | + | * [[Fertilisation, Implantation and Early Embryonic Development -Bovine Freemartinism - Anatomy & Physiology|Bovine Freemartinism]] |
| − | |||
Revision as of 09:50, 11 August 2008
Introduction
Sexual differenciaton by default follows a pathways for development of female internal and external genitalia, requiring no active intervention. Endocrine activity of the testes, production of Androgens by Leydig cells and Mullerian Inhibiting hormone by Sertoli cells, is required for sexual differenciation to be diverted down the male genitalia development pathway.
Internal Genetalia
- Male: The primitive male reproductive tract The Wolffian Duct developes from the Mesonephric Duct
- Female: The primitive female reproductive tract Mullarian Ducts develop from the Paramesonephric Duct
- This is dependent on appropriate hormonal influence.
Male
- MIH from Sertoli cells and Androgens from Leydig cells prevent spontaneous development of female internal genetalia.
- Androgens actively maintain Wolffian Ducts, which give rise to male internal genetalia:
- Epididymis
- Vas Deferens
- Vesicular Glands/ Seminal Vesicles
- MIH causes Mullarian Ducts to regress
Female
- Wolffian Ducts spontaneously regress in absence of Androgens.
- Mullarian Ducts persist to give rise to female internal genetalia:
- Oviducts
- Uterus
- Cervix
- Cranial Vagina
- Normal Ovarian activity is NOT essential for the development of normal female internal genetalia.
External Genetalia
Male
- Potential to develop male of female external genetalia. Testosterone is required to develop male external genetalia.
- Androgen secretion from the Testes induces:
- Urethral folds to fuse to allow enclosure of the urethral tube. This, together with the cells from the genital swelling, forms the shaft of the Penis.
- Genital swellings fuse in the midline to allow formation of the Scrotum
- Genital Tubercle expands to give rise to the Glans Penis
Female
- Development is ensured by the absence of Testosterone, it is independent of Ovarian endocrine activity.
- Urethral folds and Genital Swellings remain separate to form the Labia Minora and Majora.
- Genital tubercle forms the Clitoris
- Exposure of the female tract to Androgens will masculinise external genetalia.
- Failure of proper endocrine communication between the gonads, internal and external genitalia can lead to dissociation of gonadal and genital sex.
Sexual Differentiation of the Brain
Male
- Testosterone secreted into the blood reaches the brain.
- Converted to Dehydrotestosterone and Oestradiol by Aromatase enzymes in the Hypothalamus.
- Oestradiol masculinises the brain
Female
- Alpha Fetoprotein binds Oestradiol, preventing it from crossing the blood-brain barrier.
- Oestradiol cannot access the Hypothalamus
- Protects female brain from masculising effects of Oestradiol.