Endocrine - Gonad Development
Embryonically, initial endocrine development of the testis is required for development of both the internal genital tract and the external genitalia.
Postnatally, the gonads are part of an integrated Hypothalamus-Pituitary-Gonad (HPG) axis.
- mesoderm - mesothelium and underlying mesenchyme, primordial germ cells
- Gonadal ridge - mesothelium thickening, medial mesonephros
- Primordial Germ cells - yolk sac, to mesentery of hindgut, to genital ridge of developing kidney
- testis-determining factor (TDF) from Y chromosome: presence (testes), absence (ovaries)
- 8 Weeks, mesenchyme, interstitial cells (of Leydig) secrete testosterone, androstenedione
- 8 to 12 Weeks - hCG stimulates testosterone production
- Sustentacular cells - produce anti-mullerian hormone to puberty
- X chromosome genes regulate ovary development
Androgen and Digit ratio (2D:4D)
The ratio of 2nd and 4th finger (D, digit) length. This ratio has been suggested to relate to high fetal testosterone concentration (males have lower 2D:4D than females) and has been shown for several species. Although a study in mice has not shown the same correlation. There have been some suggestions that the ratio may also be an indicator of various neurological abnormalities.
To measure (2D:4D) - using your right hand palm up, measure the index finger (2) and ring finger (4) length from palm to tip. Dividing the index finger by the ring finger gives the 2D:4D ratio, average women ratio is 1, average men is 0.98.
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Cite this page: Hill, M.A. (2020, October 19) Embryology Endocrine - Gonad Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Endocrine_-_Gonad_Development
- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G