BGDB Sexual Differentiation - Fetal
Practical 12: Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | 2011 Audio |
Introduction
In the previous section we observed late embryonic male genital development and now in fetal development we will observe early fetal female development. Then we will explore fetal development of the external genitalia and gonadal descent.
Week 10 Female
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Plane A (most lateral) | Plane B (lateral) |
Plane C (medial) | Plane D (midline) |
Uterus and Vagina
Mouse paramesonephric duct (Müllerian duct)[1] |
This mouse image shows the relationship between the mesonephric and paramesonephric ducts opening into the urogenital sinus.
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<mediaplayer width='490' height='500' image="http://embryology.med.unsw.edu.au/embryology/images/2/2d/Uterus_001_icon.jpg">File:Uterus_001.mp4</mediaplayer> | Female Uterus and Vagina (between week 9 and 20)
The uterus and broad ligament will eventulaly divide the pelvic cavity into two separate pouches.
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This graph shows the growth during the fetal period of the uterus between week 19 and 38.[2]
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External Genitalia
This next section will look at the development of the external genitalia using a series of animations and online resources.
Female External Genitalia
<mediaplayer width='270' height='380' image="http://embryology.med.unsw.edu.au/embryology/images/3/37/Male_external_001_icon.jpg">File:Female_external_001.mp4</mediaplayer> | Animation showing the development of external female genitalia from the indifferent external structure (week 9 to 12 approximately).
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Male External Genitalia
<mediaplayer width='270' height='380' image="http://embryology.med.unsw.edu.au/embryology/images/3/37/Male_external_001_icon.jpg">File:Male_external_001.mp4</mediaplayer> | Animation showing the development of external male genitalia from the indifferent external structure (week 9 to 12 approximately).
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External Genitalia Comparison
Gonad Descent
<mediaplayer width='296' height='430' image="http://embryology.med.unsw.edu.au/embryology/images/7/75/Gonad_blood_01_icon.jpg">File:Gonad blood 01.mp4</mediaplayer> | Animation shows the descent of the gonads and their blood supply.
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Internal Gonad Descent
Testes Descent
Start of testis descent | End of testis descent |
Additional Information
Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page. |
Testes Descent Timeline
Data from a study of male human fetal (between 10 and 35 weeks) gonad position.[3]
- 10 to 23 weeks - (9.45%) had migrated from the abdomen and were situated in the inguinal canal
- 24 to 26 weeks - (57.9%) had migrated from the abdomen
- 27 to 29 weeks - (16.7%) had not descended to the scrotum
A second study looked at the position of the testes[4]
- 33 weeks fetal testes had descended to the scrotum
- between 33 to 40 weeks (term) both testes have normally descended to the scrotum
Failure of descent (cryptorchidism) either unilateral or bilateral testicular descent, occurring in up to 30% premature and 3-4% term males.
Cryptorchidism in common eutherian mammals.[5]- Species comparison of descent timeline
Historic Genital Images
Practical 12: Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | 2011 Audio |
References
BGDB: Lecture - Gastrointestinal System | Practical - Gastrointestinal System | Lecture - Face and Ear | Practical - Face and Ear | Lecture - Endocrine | Lecture - Sexual Differentiation | Practical - Sexual Differentiation | Tutorial
Glossary Links
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Cite this page: Hill, M.A. (2024, March 19) Embryology BGDB Sexual Differentiation - Fetal. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Sexual_Differentiation_-_Fetal
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G