Reproductive roles Male’s job is to get the sperm to the egg The sperm are specialized to deliver the male’s genes to the egg Female’s job is to produce a gamete (egg) containing the female’s genes Egg is specialized to nourish the embryo Egg is large and contains nutrients Egg must be moved along Female must also nourish and protect the embryo and fetus This is the job of the uterus Male reproductive strategy: Produce millions of gametes and hope that one makes it to the egg Female reproductive strategy:
Testes in male b. Ovaries in females 1. roduce gametes Male = sperm Female = ovum or egg join zygote; new individual 2. produce sex hormones testosterone estrogen + progesterone Male Reproductive System Testes located in scrotum why? sperm don’t survive well at body temperature is 3-4o F cooler temp kept constant by reflex how? – pass through the inguinal canal before birth hole usually closed over with connective tissue possible problems 1. cryptorchidism failure of the testes to descend if not corrected, results in sterility corrected by surgery or by administering hormones 2. inguinal hernia inguinal canal does not completely close intestine may push into opening correct with surgery more common in men but may occur in women Inside Testes 1. eminiferous tubules about 1000 site where sperm are produced by a process called spermatogenesis produce 100 million+ sperm each day from puberty until death spermatogenesis
A. takes place in an orderly progression from the outside edge of seminiferous tubule to inside (lumen) B. involves changes in genetic information and changes in the shape and functioning of cell sperm carry father’s genetic contribution to next offspring body cells have 2 copies of each chromosome (1 from Mom ; 1 from Dad) gametes (egg or sperm) can have only 1 copy of each chromosome meiosis = the type of cell division that produces gametes 1 cell with 2 copies of each chromosome Meiosis spermatogenesis 4 cells with 1 copy of each chromosome Sperm Structure 2 designed to deliver male’s genetic contribution to next generation 1.
Head – contains male’s genetic contribution to next generation; almost all nucleus 2. Acrosome – a sac containing enzymes to will allow the sperm to digest the outer layers around egg so sperm nucleus can reach egg nucleus 3. Mitochondria – energy to fuel the trip to egg 4. Tail (or flagellum)—has contractile fibers for motility; allows the sperm to swim to egg 2. interstitial cells – produce male sex hormone – testosterone Still in testis – between seminiferous tubules Beginning at puberty these cells secrete testosterone They are stimulated to secrete testosterone by LH, a hormone produced by the anterior pituitary gland LH (from anterior pituitary) stimulates the release of testosterone
HORMONES chemical messengers produced by certain glands and released into the blood hormone reaches all cells only cells with a receptor for that hormone can respond a cell responds by doing what that cell does it might divide it might produce a chemical it might increase rate of certain chemical reactions so hormones have different effects on different cells cells without receptors for that hormone cannot respond 3 Cell 1 (with receptor) Effect 1 Cell 2 (with receptor) Effect 2 Hormone Into blood supply throughout body Cell 3 (with receptor) Effect 3 Cell 4 (no receptor) No Effect Testosterone causes: development of male reproductive apparatus sperm maturation secondary sex characteristics sex drive (in part) Possible problems with testes Testicular cancer: most common in males 25-30 yrs. more common if testes did not descend after 6 yrs. may be hereditary usually does not cause pain Practice self exam! Feel for small lump
Best done after a hot shower Sperm next enter a system of tubes to store and transport sperm 1. pididymis: tube about 20 feet long stores sperm sperm mature here, sperm change size and shape, metabolism changes, sperm become capable of moving but don’t yet. sperm moved along by peristalsis (a wave of muscle contraction) 2. vas deferens: sperm duct conducts sperm from epididymis to urethra 3. urethra: conducts sperm to outside of body, also conducts urine but never at same time Accessory Glands: 1. Bulbourethral glands mucous secretion just before ejaculation lubricant? Buffers to adjust pH of urethra 2. Prostate gland secretes fluid, milky color alkaline activates sperm counteracts acidity of female reproductive tract Possible problems with prostate 1. enlarges in older men difficulty urinating & decreased bladder volume 2. rostate cancer grows slowly can spread detected by: rectal exam and blood test for PSA (prostate specific antigen)
Seminal vesicles make up most of the volume of semen secretion probably nourishes sperm (contains fructose, vitamin C, amino acids, prostaglandins) Result = semen Semen: secretions of accessory glands and sperm about 1 tsp. per ejaculation, about 20 % sperm Functions: transport sperm lubricate passageways nourish sperm decrease acidity of female reproductive tract Penis: Functions: transfer sperm to female conducts sperm outside body tip is enlarged = glans penis (rich in sensory endings) Mechanism of erection 3 columns of spongy tissue arteries dilate ? increase blood delivery veins close down blood accumulates