How Human Reproduction Works

Other Sexual Organs

Although not located in the reproductive systems, two other organs are important for sexual function in both males and females:

The hypothalamus in the brain -- The hypothalamus has nerve cells that secrete a hormone called gonatotropin releasing hormone (GnRH) into the blood vessels leading to the anterior pituitary gland.
The anterior pituitary gland just beneath the brain -- GnRH causes the anterior pituitary cells to release two hormones, luteinizing hormone (LH) and follicle stimulating hormone (FSH), into the general blood circulation. LH and FSH act on the testes/ovaries to stimulate the making and maturation of the sex cells and the production of sex hormones (testosterone, estrogen and progesterone).

The nerve cells time-release small, low-level spurts of GnRH every 90 minutes, which causes the anterior pituitary to secrete small pulses of LH and FSH. The sex hormones from the testes/ovaries give feedback to the hypothalamus and anterior pituitary to regulate the secretion of GnRH, LH and FSH -- this interplay is called the negative feedback control system. The chemical interplay between the hypothalamus, anterior pituitary gland and the testes/ovaries is important for sexual development, maintaining sexual function and sexual reproduction. An error in this chemical interplay can be a cause of infertility.