8.5 Reproduction and Hormones

Human Male Reproductive System Organ Structure and Function Testes Located in the scrotum out side the body. composed of tightly coiled tubules that produce sperm. The surrounding tissue produces the male hormones Testes produce sex hormones (androgens): testosterone (more potent and abundant) and andosterone. Production of testosterone starts during fetal development continues for a short time after birth, nearly stops during childhood, and then resumes at puberty. This steroid hormone is responsible for: - The growth and development of the male reproductive structures - Increased skeletal and muscular growth - Enlargement of the larynx accompanied by voice changes - Growth and distribution of body hair - Increased male sexual drive

Composed of 3 cylinders of spongy erectile tissue. Epididymis Newly produced sperm is stored in this tube just outside and to the rear of each testicle. Here the sperm will develop. Vas deferens A muscular duct that connects the epididymis and the ejaculatory duct. It carries sperm out toward the urethra during ejaculation. Ejaculatory duct the area formed by the union of the two vas deferens ducts (one from each testis) and the duct from the seminal vesicles. Urethra The tube that runs through the penis and drains the excretory and reproductive systems. Seminal Vesicles Gland located behind the bladder and empty into the ejaculatory duct. Mucus, amino acids, fructose and prostaglandins are found making up the fluid. Makes up 60% of semen volume. Prostate Gland Large gland that surrounds the upper portion of the urethra. Gives off a thin milky secretion containing several enzymes. It neutralizes the acidic urine residue in the urethra and activates sperm. Bulbourethral Glands Glands below the prostate that empty into the urethra at the base of the penis. Unclear function Penis Composed of 3 cylinders of spongy erectile tissue.

Human Female Reproductive System Organ Structure and Function Ovaries Each ovary contain many follicles (one egg surrounded by follicle cells). Formed at birth. Starting at puberty one follicle matures and releases an egg during each menstrual cycle. Produces estrogen and progesterone These steroid hormones are responsible for: - Development of breasts - Distribution of fat evidenced in the hips, legs, and breasts - Maturation of reproductive organs such as the uterus and vagina Progesterone causes the uterine lining to thicken in preparation for pregnancy.

Neck of the uterus which opens to the vagina. Fallopian Tubes Do not touch the ovaries. Funnel like opening surrounded with cilia. Houses the mature egg and is the site of fertilization. Distil end connects to the uterus. Uterus Thick muscular organ shaped like an inverted pear. 7 cm long and 4-5 cm wide. The lining is the endometrium, it is richly supplied with blood vessels. Cervix Neck of the uterus which opens to the vagina. Vagina Thin walled chamber serves as a repository for the semen and forms the birth canal.

Female Menstrual Cycle Phase Function Menstrual Flow Phase During this time most of the endometrium is being lost from the uterus. It lasts a few days. The first day of this phase is designated as Day 1 of the cycle. Proliferative Phase Lasts for 2 or 3 weeks. It involves the regeneration and thickening of the endometrium. Secretory Phase Lasts about 2 weeks. The endometrium continues to thicken and become more vascularized, and produces glands that produce glycogen rich fluid. If the embryo is not implanted the flow phase begins.

High concentrations of LH stimulates final maturation and ovulation. Ovarian Cycle An ovarian cycle parallels the menstrual cycle. This cycle consists of three steps. Phase Function Hormones Involved Follicular phase Several follicles within the ovary begin to grow. The egg cells within the follicles enlarge and only one continues to grow while the others degenerate. A fluid filled cavity develops in the maturing follicle causing a bulge on one side of it. GnRH is secreted by the hypothalamus which stimulates the anterior pituitary to secrete small amounts of FSH and LH. FSH stimulates the follicles to produce estrogen. As estrogen increases it causes GnRH secretion to increase as well as FSH and LH. Ovulatory phase This is the time ovulation occurs. The follicle and the adjacent wall of the ovary rupture and release the egg. High concentrations of LH stimulates final maturation and ovulation. Luteal phase The follicular tissue remaining in the ovary forms a corpus luteum. This is an endocrine gland that secretes female hormones. High concentrations of LH cause the follicle to form the corpus luteum. The corpus luteum secretes estrogen and increasing amounts of progesterone. This inhibits the production of GnRH which also decrease the production of LH and FSH. Low LH causes the corpus luteum to degenerate resulting in lower estrogen and progesterone levels.

The typical female reproductive cycle occurs every 28 days The typical female reproductive cycle occurs every 28 days. Briefly, the events occurring within the cycle are: 1. Menstruation from previous cycle occurring. 2. FSH levels are high. 3. FSH stimulates development of primary follicles. 4. Primary follicles grow, secrete estrogen, and then form secondary follicle. 5. Estrogen from follicle inhibits FSH from anterior pituitary gland, stimulates further follicular growth and increased secretion of estrogen, and stimulates growth of endometrial lining (proliferative phase of the uterus). 6. LH surge.

The typical female reproductive cycle occurs every 28 days The typical female reproductive cycle occurs every 28 days. Briefly, the events occurring within the cycle are: 7. Ovulation occurs. 8. Remaining follicular cells are converted into the corpus luteum. 9. Corpus luteum secretes progesterone and smaller amounts of estrogen. 10. Progesterone stimulates the endometrial glands to secrete and accumulate mucus and glycogen (secretory phase of uterus). 11. Corpus luteum degenerates. 12. Progesterone and estrogen secretion decreases. Menstruation of next month's cycle begins.