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Gonad
From Wikipedia, the free encyclopedia
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, sperm and egg cells are gametes. Although medically the gonad term can refer to either male gonads (testicles) or female gonads (ovaries), the vernacular, or slang use of "gonads" (or "nads") usually only refers to the testicles.
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In addition to producting gametes, the gonads are a combined glands providing both exocrine and endocrine functions. The male and female gonads produce steroid sex hormones, identical to those producted by adrenal cortical cells. The major distinction is the source and relative amounts produced.
The male gonads, known as the testes or testicles, secrete a class of hormones called androgens, and produce spermatozoa. The predominant androgen in males is testosterone.
In females, the female gonads, known as the ovaries, secrete a hormone estrogen and progesterone, as well as ova. The dominant estrogen is known as estradiol, which is derived from testosterone.
The gonads are controlled hormonally by luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secreted by the anterior pituitary gland. The anterior pituitary gland's excretion of LH and FSH are, in turn, controlled by the hypothalamus' gonadotropin-releasing hormone.
Gonads start developing as a common anlage, in the form of gonadal ridges, and only later are differentiated to male or female sex organs. The SRY gene, located on the Y chromosome and encoding the testis determining factor, decides the direction of this differentiation.
In 1943, Matthew Browne started a development of gonads in a part of the development of the urinary and reproductive organs.[citation needed]