secondary sex characteristics. You should know that, in women, testosterone is also secreted by the female ovaries but in a smaller amount than is seen in males. The endocrine system controls the production of testosterone. It all starts with the release of gonadotropin releasing hormone or GnRH from the hypothalamus. This happens steadily in males but is cyclical in females. The GnRH causes the pituitary gland to make follicle stimulating hormone or FSH and luteinizing hormone or LH. The FSH is responsible for Sertoli cell function and spermatogenesis. Sertoli cells make inhibin, which is a peptide hormone that feeds back to block FSH release. The LH triggers the Leydig cells to make testosterone. The entire process is a type of negative feedback system. Low testosterone concentrations will increase GnRH production by the hypothalamus, which sets the process in motion. When testosterone levels are considered high enough, the testosterone will block both the GnRH release and the LH release. The same thing happens to the feedback loop involved in FSH secretion.
FEMALE REPRODUCTIVE SYSTEM The female reproductive system is responsible for making the female gamete, which is called an oocyte. There are internal and external structures in the female reproductive system. Figure 7 shows the external genitalia in the female:
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