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A testicle or testis (pl. testes) is the gonad in all male bilaterians, including humans, and is homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The release of testosterone is regulated by luteinizing hormone (LH) from the anterior pituitary gland.
ot. The genital ridge from which either the ovary or testis is formed. o. The left ovary: t. Testis in the place of its original formation; t', together with the dotted lines above, indicates the direction in which the testis and epididymis descend from the abdomen into the scrotum. Skene's glands a.k.a. paraurethral gland: pr. Prostate: u. Uterus.
The presence of the SRY gene, [8] located on the short arm of the Y chromosome and encoding the testis determining factor, usually determines male sexual differentiation. In the absence of the SRY gene from the Y chromosome, usually the female sex (ovaries instead of testes) will develop.
The ovary is thus formed mainly from the genital ridge and partly from the mesonephros. Later the mass is differentiated into a central part, the medulla of ovary, covered by a surface layer, the germinal epithelium. Between the cells of the germinal epithelium a number of larger cells, the immature ova, are found.
In animals (including humans), the male sex organs include the testicles, epididymides, and penis; the female sex organs include the clitoris, ovaries, oviducts, and vagina. The testicle in the male and the ovary in the female are called the primary sex organs. [1] All other sex-related organs are known as secondary sex organs.
Since the scrotum, where the testes is present, is situated outside the body cavity, it provides a temperature about 3 °C below normal body temperature. In females, gametogenesis is known as oogenesis; this occurs in the ovarian follicles of the ovaries. This process does not produce mature ovum until puberty.
Gonadal sex refers to the gonads, that is the testicles or ovaries, depending on which genes are expressed. Phenotypic sex refers to the structures of the external and internal genitalia. [6] Six weeks elapse after fertilization before the first signs of sex differentiation can be observed in human embryos. [5]
The ovary is differentiated into a central part, the medulla of ovary, covered by a surface layer, the germinal epithelium. The immature ova originate from cells from the dorsal endoderm of the yolk sac. Once they have reached the gonadal ridge they are called oogonia. Development proceeds and the oogonia become fully surrounded by a layer of ...