Internal and External Genitalia Development - Anatomy & Physiology
Revision as of 09:26, 11 August 2008 by Amycartmel (talk | contribs) (New page: ==Introduction== = Internal Genetalia = * Male: '''Wolffian Duct''' developes from the '''Mesonephric Duct''' * Female: '''Mullarian Ducts''' develop from the '''Paramesonephric Duct''' ...)
Introduction
Internal Genetalia
- Male: Wolffian Duct developes from the Mesonephric Duct
- Female: 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.