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Gonad
Ovaries of Cyprinus carpio.png
A pair of ovaries of Cyprinus carpio (common carp) placed in dissecting dish
Identifiers
MeSHD006066
FMA18250
Anatomical terminology

A gonad, sex gland, or reproductive gland[1] is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm.[2] The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells. Both of these gametes are haploid cells. Some hermaphroditic animals have a type of gonad called an ovotestis.

Evolution

It is hard to find a common origin for gonads, but gonads most likely evolved independently several times.[3]

Regulation

The gonads are controlled by luteinizing hormone and follicle-stimulating hormone, produced and secreted by gonadotropes or gonadotrophins in the anterior pituitary gland.[4] This secretion is regulated by gonadotropin-releasing hormone produced in the hypothalamus.[5][6]

Development

Main article: Development of the gonads

Gonads start developing as a common primordium (an organ in the earliest stage of development), in the form of gonadal ridges,[7] and only later are differentiated to male or female sex organs. The presence of the SRY gene,[8] located on the Y chromosome and encoding the testis determining factor, determines male sexual differentiation. In the absence of the SRY gene from the Y chromosome, the female sex (ovaries instead of testes) will develop. The development of the gonads is a part of the development of the urinary and reproductive organs.

See also

References

  1. ^ "the definition of sex gland". Dictionary.com. Archived from the original on 22 July 2015. Retrieved 8 May 2018.
  2. ^ "gonad (noun) American English definition and synonyms - Macmillan Dictionary". www.macmillandictionary.com. Archived from the original on 8 May 2018. Retrieved 8 May 2018.
  3. ^ Schmidt-Rhaesa, Andreas (2007-08-30). The Evolution of Organ Systems. Oxford University Press. p. 252. ISBN 978-0-19-856668-7.
  4. ^ "gonadotropin". The Free Dictionary. Mosby's Medical Dictionary, 8th edition. Elsevier. 2009. Retrieved 4 June 2012.
  5. ^ John W. Kimball (12 February 2011). "Hormones of the Hypothalamus: Gonadotropin-releasing hormone (GnRH)". Kimball's Biology Pages. John W. Kimball (The Saylor Foundation). Archived from the original on 27 June 2012. Retrieved 4 June 2012.
  6. ^ Marieb, Elaine (2013). Anatomy & physiology. Benjamin-Cummings. p. 915. ISBN 9780321887603.
  7. ^ Satoh, Masahito (August 1991). "Histogenesis and organogenesis of the gonad in human embryos". Journal of Anatomy. 177: 85–107. PMC 1260417. PMID 1769902.
  8. ^ "Human Developmental Genetics". Institut Pasteur. Institut Pasteur. Archived from the original on 5 May 2012. Retrieved 4 June 2012.