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| | This abnormal development occurs where is a urethral opening at the base of the penis. This abnormality has been linked to environmental factors. | | This abnormal development occurs where is a urethral opening at the base of the penis. This abnormality has been linked to environmental factors. |
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| − | ==EMBRYOLOGICAL DEVELOPMENT OF THE GENITAL TRACT==
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| − | ===Early embryo===
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| − | *Small indifferent gonads.
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| − | *Primitive structures which will become gonads and genital tract are identical at this stage.
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| − | *Paired mesonephric ducts (Wolffian) or paramesonephric (Mullerian) ducts fuse caudally with urogenital sinus.
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| − | (Metanephros - becomes the kidney).
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| − | ===Gonadal differentiation===
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| − | *Determined by the presence of the SRY gene of the Y chromosome (sex determining region of the Y chromosome) which encodes “testicular determining factor” protein (SRY protein).
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| − | *Lack of SRY gene (i.e. XX females) leads to ovarian differentiation.
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| − | ===Development of phenotypic sex===
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| − | *The sex of the embryonic gonad normally determines which reproductive duct system develops.
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| − | *Testes induce development of mesonephric (Wolffian) duct system in to epididymis and vas deferens and cause regression of paramesonephric (Mullerian) duct by ”mullerian inhibitory substance”, (MIS).
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| − | *Absence of testes in presence of ovaries allows paramesonephric ducts to develop under influence of oestrogen to oviduct, uterus, cervix and cranial vagina.
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| − | ===Summary of determinants of sexual development===
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| − | Chromosomal or genetic sex = sex chromosomes
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| − | <br>Gonadal sex = ovary or testis
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| − | <br>Phenotypic sex = usually determined by gonad
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| − | <Br>Information by permission of Professor RW Else
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| − | {{unfinished}}
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| | [[Category:To Do - A&P]] | | [[Category:To Do - A&P]] |
| | [[Category:Developmental Biology]] [[Category:Reproductive System - Anatomy & Physiology]] | | [[Category:Developmental Biology]] [[Category:Reproductive System - Anatomy & Physiology]] |