The male reproductive system serves to produce sperm via meiotic cell division within the seminiferous tubules of the testes. These sperm cells are stored in the epididymides, where they also mature. Sperm are conducted to the outside of the body by the vasa deferentia, and, within the penis, the urethra. The sperm are carried within seminal fluid, which is the product of secretions from the seminal vesicles, prostate gland, and bulbourethral glands. Orgasm in males follows erection and sexual stimulation, and involves ejaculation. Two hypothalamic hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), regulate the functioning of the testes (LH is also called interstitial cell stimulating hormone or ICSH in males). FSH promotes the formation of sperm (spermatogenesis), and LH causes the testes to produce and release testosterone. Testosterone is necessary for the production of sperm, and maintains the male secondary sexual characteristics. The female reproductive system serves to produce eggs, and house developing offspring. Eggs are produced in follicles within ovaries and egg production is called oogenesis. Ovulation involves the release of an egg from an ovary, typically occurs once a month, and produces an empty follicle called a corpus luteum. The corpus luteum will persist for 3–6 months if pregnancy occurs. The egg released from the ovary travels down the uterine tube where fertilization may occur. Eventually the egg (or developing embryo if fertilization has occurred) will implant in the lining of the uterus. The vagina is inferior to the uterus and serves as both the birth canal and the organ for sexual intercourse. The regulation of female hormone levels begins with the anterior pituitary’s secretion of FSH and LH. FSH promotes the development of a follicle in the ovary and the secretion of estrogen by the follicle. LH promotes the development of the corpus luteum, which secretes progesterone. These events are part of the ovarian cycle which lasts an average of 28 days. Estrogen and progesterone regulate the uterine cycle in which the uterine lining, or endometrium, builds up and is then shed during menstruation. Menstruation does not occur during pregnancy because of hormones produced by the placenta. The text explains various methods of birth control and describes their effectiveness. Infertility is also discussed, as are a variety of sexually transmitted diseases.