Male Reproductive System A PII Final Exam 1 The parasympathetic nervous system stimulates an increase in Nitric Oxide causing relaxation and vasodilation of arterioles so erectile bodies fill with blood resulting in an erection PNS point The sympathetic nervous system stimulates spinal reflex causing contraction of ducts glands and bulbospongiosus muscles and constriction of the bladder resulting in the propulsion of semen from the male duct system aka ejaculation SNS shoot 2 The testes serve two distinct physiological roles endocrine and exocrine Exocrine function is the production of mature sperm spermatogenesis involving seminiferous epithelium and Sertoli cells Exocrine function is the production of androgens steroidogenesis involving interstitial compartment and Leydig cells 3 Spermatogenesis takes place in the seminiferous tubules of the testes and produces sperm It begins at about 14 years old and makes 4 million sperm every day There are 3 phases of spermatogenesis Proliferative Phase I i There are 3 types of spermatogonia Type Ad dark dense chromatin Type Ap pale less dense chromatin and Type B ii Type Ad gives rise to a Type Ap as well as generating more Type Ad for future generations of sperm Type Ap then gives rise to Type B II Meiotic Phase i Meiosis I Type B spermatogonia divide by mitosis into primary spermatocytes and replicated chromosomes seek out a partner After Meiosis I each daughter cell has 2 copies and the number of chromosomes is cut in half from 46 to 23 1 Crossing over occurs during Meiosis I causing portions of nonsister chromatids to exchange places resulting in two recombinant chromatids with separate gametes III ii Meiosis II further division but the same number of chromosomes 23 Spermiogenic Phase is the differentiation of a spermatid into a sperm through 4 steps i Golgi Phase tail filament appears ii Cap Phase head cap appears from acrosomal granule iii Acrosome Phase nucleus and head cap elongate and acrosomal granule differentiates to form acrosome iv Maturation Phase cell completes differentiation to become a mature sperm Spermatogonia initiate a new cycle every 16 days and there are 4 total cycles 64 days i ii iii iv 1st Type A gives rise to Type B 2nd Primary spermatocytes of 1st cycle form 3rd Spermatids of first cycle appear 4th Spermatogenesis completed spermiation begins Once sperm are released into lumen another 10 days is required for movement to epididymis 74 days Sperm is then stored in the epididymis 4 The hypothalamus releases GnRH to the pituitary gland stimulating the production of FSH and LH FSH binds to receptors in Sertoli cells circulating down through seminiferous tubules initiating sperm production and also increasing ABP FSH also increases the number of LH receptors on Leydig cells LH binds to Leydig cells stimulating testosterone production Testosterone assists in sperm production and inhibits the pituitary gland while inhibin inhibits the hypothalamus 5 Sperm migration through the epididymis takes 10 16 days meaning 90 days total for mature sperm to appear in ejaculate Sperm is stored in cauda epididymis and vas deferens but NOT in seminal vesicles Maturational changes are that the sperm acquire the capacity for motility in epididymis Elimination of aged sperm occurs through phagocytosis Ejaculate consists of seminal plasma secretions from accessory sex glands and semen combination of seminal plasma and sperm Order of ejaculation Cowper s Littre prostate ampulla and epididymis seminal vesicles sperm may be present in first portion I II III Cowper s gland is about 1 2 ml or 5 of ejaculate It is clear fluid rich in microproteins that lubricates the distal urethra It may contain small amounts of sperm Prostate gland is about 5 ml or 15 30 of ejaculate containing citric acid acid phosphate calcium and zinc It liquefies the ejaculate Prostate specific antigen PSA helps to activate sperm motality no sperm Seminal Vesicles are about 2 2 5 ml or 45 80 of ejaculate rich in fructose and prostaglandins It contains enzymes which cause coagulation of ejaculation The absence of fructose is used to diagnose an absence of vas deferens in the epididymis most sperm Female Reproductive System 1 In the fetal period oogenesis produces female sex cells Oogonia stem cells divided by mitosis are transformed into primary oocytes Primary oocytes begin meiosis but most don t complete it Oogonia peak at 20 weeks and then undergo meiosis when the number greatly diminishes Oogonia are present in fetus between weeks 5 30 Mother cell Mitosis Primary oocytes Meiosis I first polar body meiosis II may or may not occur and secondary oocytes meiosis II completed only if sperm penetration occurs polar bodies secondary polar bodies ovum Oogenesis begins 6 8 weeks reaching 6 7 million oogonia by 16 20 weeks maximal oogonial content of gonad Store of oocytes becomes depleted 50 years later Women will have all the eggs she will need by 20 weeks in the womb Having children over 35 40 years old could cause abnormalities 2 The Ovarian Cycle a Follicular Phase the period of follicular growth days 1 14 FSH follicle stimulating hormone develops about 20 follicles at the beginning of each cycle but only one develops and the rest undergo atresia degeneration The developing follicle has enough estrogen to be maintained due to theca and granulose cells on the follicle Two Cell Theory LH induces androstenedione synthesis in theca cells Driven by FSH stimulus granulosa cells process androstenedione into estrone which is further converted to estradiol 1 Basically theca cells make androgens which are transferred to granulosa cells to make estrogen b Midcycle when ovulation occurs 14 days Development of estrogen making follicle Surge in LH correlates with ovulation The release of prostaglandins allows the egg to come out and upon release the release of the egg the corpus luteum required for pregnancy is formed which makes progesterone Progesterone must be present for pregnancy to be maintained c Luteal Phase period of corpus luteum activity days 14 28 After ovulation the ruptured follicle collapses and forms the corpus luteum which secretes estrogen and progesterone If pregnancy does NOT occur the corpus luteum degenerates in 10 days If pregnancy DOES occur the corpus luteum produces hormones until the placenta takes over at about 3 months Basal body temperature increases during the luteal phase due to progesterone The length of cycles can vary from 21 to 40 days but the
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