Reproductive System Basic function = production of a newborn Processes included: 1. Generating the gametes (ova and sperm) 2. Bringing ova and sperm together 3. Development of fertilized ovum 4. Birth of the newborn 5. Nourishment/maintenance of the newborn Primary organs that produce gametes are the gonads: Testes in male – also secrete testosterone Ovaries in female – also secrete estrogens and progesterone

Other Components of Reproductive System Reproductive tract = structures through which gametes travel Accessory sex glands (secrete fluids into reproductive tract) External genitalia Secondary sex characteristics: body contours, hair distribution, muscle definition, depth of voice, width of pelvis, etc.

Roles of female reproductive system: 1.Produce ova 2.Bring sperm and ova together 3.Maintain the embryo (2 months) and fetus 4.Deliver the newborn 5.Provide nourishment to the infant Role of male reproductive system: 1.Produce and deliver sperm 2.That’s it. There’s only one.

Puberty This is the period when reproductive system develops adult characteristics. Typically begins between ages 10 and 14, lasts from 3 to 5 years. Production of sperm and ova begin Production of sex hormones begins (all are steroids, like adrenocortical hormones)

Male Reproductive System This shows male reproductive tract and accessory sex glands. Note that testes are suspended outside the body cavity, in the scrotum.

Scrotal temperature is normally around 92 F; about 7 degrees below body temperature. This is important because normal sperm development doesn’t occur above 96 F. Scrotal muscles respond to temperature via a spinal reflex, bringing the testes closer to or further from the body as external temperature varies.

Cryptorchidism Embryonic testes develop within body cavity. Normally, testes descend into scrotum at about 7 months gestation, when testosterone secretion begins. Testosterone secretion stops soon after birth, doesn’t start again until puberty - prepubertal boys produce no testosterone. Sometimes one or both testes are undescended at birth. Descent usually occurs spontaneously within a day or two, can be induced with testosterone if necessary. Undescended testis in adult is cryptorchidism; that testis is sterile. Testicular warming was a fairly common method of contraception in US until about 1940.

Seminiferous tubules, about 75% of testicular mass, produce sperm. Interstitial (= Leydig) cells surround the seminiferous tubules, produce testosterone. Since testosterone is a steroid, it diffuses from interstitial cells into seminiferous tubule cells as well as being secreted into circulation.

Effects of Testosterone In absence of testosterone from fetal testes, fetus will develop with female characteristics. Testosterone masculinizes reproductive tract and external genitalia, cause testicular descent. Testosterone secretion stops at birth, resumes at puberty. This causes growth and maturation of male reproductive system (including sperm production) and maintains it in adult. Removal of gonads (castration) in adult males -> eunuch. Male reproductive system regresses to prepubertal state, as do secondary sex characteristics (facial hair, deepened voice, muscle definition, body hair, etc.) and sex drive (libido). Castration before puberty prevents puberty from occurring. Boy sopranos were castrated in 17 th -19 th century Europe to create castratti (adult male sopranos).

Effects of Testosterone (continued) General anabolic effect Promotes protein synthesis (most striking in muscle; used by athletes for this) Promotes long bone extension (adolescent boys have spectacular growth spurts from it) Promotes calcification of epiphyseal plates, terminating growth of adolescent boys

Control of Testicular Functions Two anterior pituitary hormones involved 1.LH = ICSH promotes testosterone secretion by interstitial cells 2.FSH stimulates sperm maturation, sperm generation requires testosterone at high levels 3.LH and FSH secretion are promoted by the hypothalamic hormone, GnRH, which begins at puberty. GnRH initiates and maintains development of adult male sexual characteristics. 4.ICSH secretion is inhibited by testosterone via negative feedback