Reproductive System of Humans: Male Reproductive Organs and Functions

1. 6. Endocrine System Components: Pituitary, adrenal, thyroid, thymus, pancreas, ovaries, testes, and other ductless glands. Functions: • Produce hormones that regulate: • Blood chemistry: Levels of sugars, minerals, etc. • Reproduction • Growth • Metabolism • Digestion Homeostatic Role: • With nervous system, regulates metabolism and blood chemistry.

2. 7. Reproductive System Components: Female: Ovaries, oviduct, uterus, vagina, and associated structures Male: Testes, seminal vesicles, prostate, urethra, penis, and associated structures. Functions: • Only organ system that is not essential for individual survival. • Continuation of species. • Gamete formation (eggs and sperm cells). Homeostatic Role: • Maintains secondary sexual characteristics.

3. Reproductive System of Humans Reproductive Functions of Male: • Produces sperm • Delivers sperm to female reproductive tract All of these processes are regulated and coordinated by hormones secreted by: • Hypothalamus • Pituitary gland (anterior portion) • Testes (Sing. Testis)

4. Male Reproductive System

5. Major Organs of Male Reproductive System: • Testes: Paired male gonads. • Produce sperm through spermatogenesis, which produces four sperm cells of equal size. • Spermatogenesis occurs in a vast system of hollow tubes called seminiferous tubules. • Each mature sperm has a head, a midpiece, and a flagellum. • Sperm head has an acrosome, which produces enzymes that help it penetrate the egg. • Human sperm cannot develop at body temperature. • Testicles descend from abdominal cavity into scrotum, a skin covered sac, about two months before birth. • Undescended testicles (cryptorchidism) may cause infertility.

6. Reproductive System of Humans Major Organs of Male Reproductive System: • Epididymus: • Large coiled tube (23 ft long) that surrounds testes. • Stores sperm while they develop fertilizing ability and motility (about 20 days). • During ejaculation, sperm cells are propelled from epididymus. • Vas Deferens: • Long muscular ducts from scrotum to back of bladder. • During ejaculation, the sperm pass from epididymus into these two ducts. • Vasectomy: Each vas deferens is cut to prevent sperm from entering urethra.

7. Reproductive System of Humans Major Organs of Male Reproductive System: • Ejaculatory Duct: • Short duct after two vas deferens ducts unite. • Urethra: • Deliver sperm to the exterior. • In males, urine and sperm pass through the urethra. • Females have a separate urethra from the reproductive system.

8. Reproductive System of Humans Major Organs of Male Reproductive System: Accessory Glands: Produce semen. • Functions of semen: • Activate sperm cells • Provide nutrients for motility • Counteract acidity of vagina and male urethra • Stimulate contractions of female reproductive tract • Antimicrobial action • Ejaculation volume 4 to 5 ml. • One ejaculation has 50-500 million sperm cells • Sperm cells account for less than 5% of semen volume. • Secretions from 3 different accessory glands make up the rest of the volume: Seminal vesicles (2), prostate, and bulbourethral glands (2).

9. Major Organs of Male Reproductive System: Accessory Glands: A. Seminal vesicles (2): Secrete fluid that nourishes sperm. • Contribute about 60% of semen volume. • Thick, clear, alkaline fluid. • Contains: • Fructose: Provides energy for sperm motility. • Prostaglandins: Stimulate smooth muscle contractions of female and male reproductive tracts. • Fibrinogen: Forms temporary clot in vagina. • Sperm cells become highly motile when mixed with this fluid.

10. Accessory Glands: B. Prostate gland: Produces a thin milky secretion. • Largest of semen secreting glands. • Contributes 30% of semen volume. • Produces an antibiotic that may prevent urinary tract infections in men. • Benign (noncancerous) prostate enlargement is common among older men. • 50% of men over 40. • Almost all men over 70. • Prostate cancer is the second leading cause of cancer and cancer deaths in men. • Over 330,000 new cases/year and 40,000 deaths. • Average age at diagnosis: 72 • Detected by blood test or digital rectal exam. • Treated surgically or with drugs to reduce prostate size or activity.

11. Major Organs of Male Reproductive System: Accesory Glands: C. Bulbourethral glands (2): Release a mucous secretion that lubricates penis and facilitates its entry into vagina. • Pair of small glands below the prostate. • Contribute 5-10% of semen volume. • Before ejaculation secrete a clear mucus that neutralizes acid from remaining urine in urethra. • Bulbourethral fluid also carries some sperm that is released before ejaculation. One cause of high failure rate of withdrawal method.

12. Major Organs of Male Reproductive System: • Penis: Copulatory organ that delivers sperm to female body. • Composed of three cylinders of erectile tissue. • During sexual arousal, the penis fills with blood from the arteries. • Erection is essential for penetration. • Impotence is the inability to maintain an erection. • May be caused by alcohol, drugs, illness, and/or emotional problems. • Viagra acts by relaxing smooth muscle of penis blood vessels, allowing blood to enter erectile tissue. • Penis structure: • Shaft: Long cylinder with thick skin. • Glans: Enlarged tip of penis. Thin skin, covered by prepuce or foreskin.

13. Reproductive System of Humans Reproductive Functions of Female: • Produces eggs (ova) • Receives sperm • Incubates and nourishes the embryo and fetus • Gives birth • Produces milk for young All of these processes are regulated and coordinated by hormones secreted by: • Hypothalamus • Pituitary gland (anterior portion) • Ovaries

14. Female Reproductive System

15. Reproductive System of Humans Major Organs of Female Reproductive System: • Ovaries: Produce ova (oogenesis) and sex hormones. • Size and shape of large almonds. • Located close to lateral walls of pelvic cavity and held in place by connective tissue. • Mainly connective tissue containing scattered eggs (ova) in different stages of development. • Follicles: A single egg with surrounding cells that nourish and protect it. • Women are born with all of their follicles (40,000 to 400,000). • Only a fraction of follicles release eggs during a woman’s reproductive life.

16. Female Reproductive System: • Ovulation & Oogenesis: After puberty, each month one immature egg (oocyte), is released from ovary. • Each follicle contains a primary oocyte, arrested in prophase I of meiosis. • Pituitary hormones FSH (follicle stimulating hormone) and LH (luteinizing hormone) cause a follicle to enlarge and complete meiosis I. • One large cell (secondary oocyte) and a tiny cell (polar body) are produced. • LH (luteinizing hormone) causes the secondary oocyte to be released by the ovary during ovulation. • Oocyte will not finish meiotic division, until fertilized. • In the end, one large ovum (egg) and 3 small polar bodies are made from oogenesis.

17. Major Organs of Female Reproductive System: • Oviducts (Fallopian Tubes): Transport the egg from the ovary to the uterus. • Peristalsis of smooth muscle in oviduct and beating of cilia, help the egg move along. • Fertilization occurs in the first third of oviduct. • Scarring of oviducts is a common consequence of sexually transmitted diseases: chlamydia and gonorrhea. • Ectopic Pregnancy: Fertilized egg does not reach the uterus. Usually starts to develop in oviduct. • Usually due to a blocked oviduct. • Occurs in 1% of all pregnancies in the U.S. • Must be surgically removed. • May cause death and severe hemorrhage.

18. Reproductive System of Humans Major Organs of Female Reproductive System: • Uterus: Incubates the embryo/fetus. • Size of a fist, in center of pelvic cavity. • Oviducts open into upper corners of uterus. • Has thick walls of smooth muscle (myometrium) responsible for uterine contractions and cramps. • Endometrium: Inner mucous lining, which thickens each month in preparation for pregnancy. • If fertilization does not occur, endometrium breaks down and is discharged during menstruation. • If fertilization occurs, the egg implants in the endometrium which supports its growth until the placenta develops.

19. Reproductive System of Humans Major Organs of Female Reproductive System: • Cervix: Lower portion of the uterus, which projects into the vagina. • Pap smear: Examination of cervical tissue to detect abnormalities. Recommended yearly. • Cervical cancer: Most cases caused by a viral infection with human papillomavirus. • Women are infected through intercourse with asymptomatic male. • Takes about 20 to 30 years to develop. • Men don’t appear to be affected.

20. Reproductive System of Humans Major Organs of Female Reproductive System: • Vagina: Thin walled, muscular chamber. • Receives the sperm and penis • Acid pH kills bacteria and sperm cells • Part of birth canal • Vulva: External structures. • Clitoris: Equivalent to male penis. • Labia minora: Skin folds that border vaginal opening. • Labia majora: Protect entire genital region. • Hymen: Ring of tissue that forms a border around vaginal entrance. No known function. • Bartholin’s gland: Secrete lubricating fluid during sexual arousal. • Breasts: Lactation