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The descent of the testicles consists of the opening of a connection from the testis to its final location at the anterior abdominal wall, followed by the development of the gubernaculum, which subsequently pulls and translocates the testicle down into the developing scrotum. Ultimately, the passageway closes behind the testis.
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.
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.
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]
Male genitalia of Lepidoptera. The main component of the male reproductive system is the testicle, suspended in the body cavity by tracheae and the fat body.The more primitive apterygote insects have a single testis, and in some lepidopterans the two maturing testes are secondarily fused into one structure during the later stages of larval development, although the ducts leading from them ...
Most male fish have two testes of similar size. In the case of sharks, the testes on the right side is usually larger [citation needed].The primitive jawless fish have only a single testis, located in the midline of the body, although even this forms from the fusion of paired structures in the embryo.
Male gonad (testes, left) and female gonad (ovaries, right) Males have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall. [1] Scrotal asymmetry, in which one testicle extends farther down into the scrotum than the other, is common. This is because of the differences in the vasculature's ...
The testicles are located in the scrotum and thus outside the abdominal cavity. The ovaries of many females descend—as the testicles descend of many male mammals—and are close to the pelvic inlet at the level of the fourth lumbar vertebra. The uterus has two horns (uterus bicornis). [15]