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reproductive system.docx

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Ryerson University
Charlotte Youngson

27 -The Reproductive System Pre-lecture questions 1. What is ovulation? What hormones cause ovulation to occur? 2. Outline the events in spermatogenesis and the production of viable sperm. *NOTES • Males make 100 of gametes • Women ovulate an egg around day 14 in the 28 day cycle. Ovaries take turns creating an egg each month. • You need an open fallopian tube in order for the egg to make its way to the reproduction cycle • Menopause occurs at around 50 • In menopause the ovaries stops making the gametes and the hormones. Reproductive System • Primary sex organs (gonads): testes and ovaries • Produce sex cells (gametes) – exocrine product – released in ducts • Secrete steroid sex hormones – endocrine product • Androgens (males) • Estrogens and progesterone (females) • Made from cholesterol (lipids) • Accessory reproductive organs: ducts, glands, and external genitalia • Sex hormones play roles in • Development and function of the reproductive organs • Sexual behavior and drives (after puberty) • Growth and development of many other organs and tissues *NOTES • Indifferent gonad (conception – 8 weeks): gonads look similar • 8 weeks – the indfferent gonad start to differentiate in the genitalia that it is coded for • Male genitalia is a consequence of being surrounded by testosterone • Female genitalia is a consequence of the lack of being around testosterone therefore they develop female gonads. • Environment can be masculanized making the • Turners syndrome: the female is X • Mothers have a nesting drive whereas males have a sexual drive Male Reproductive System • Testes (within the scrotum) produce sperm • Sperm are delivered to the exterior through a system of ducts (smooth muscle) [autonomic nervous system controls – both sympathetic and parasympathetic are involved] • Epididymis, ductus deferens, ejaculatory duct, and the urethra • Accessory sex glands: seminal vesicles, prostate, and bulbourethral glands • Empty secretions into the ducts during ejaculation • Sperm at first is thick and viscous but over time it thins • Timing of liquidation of sperm is critical *NOTES • Testes can be malignant if kept in the scrotum • Restrictive undergarments can • Cooler the area the better the spermatogenesis *NOTES • Cross sectional view of male reproduction system • Scrotum is a huge site for spermatogenesis • Vasectomy – form of birth control in male – cutting of the vas deferens doesn’t produce viable sperm • Vasectomy can undone if there’s enough tissue • Prostate gland is wrapped around ejaculatory ducts and bladder – if enlarged males can experience problem = urgency to void urine (b/c of the tubing), • Drug remedies can make the prostate smaller • Prostate is a problematic gland. Breast tissue and prostatic tissue look the same • Can access it only through the rectum. If benighn nothing happens. The Testes • Sperm are conveyed through • Seminiferous tubules • Tubulus rectus • Rete testis • Efferent ductules • Epididymis • Interstitial (Leydig) cells outside the seminiferous tubules produce androgens** *NOTES • Sperm is made in the walls of the tubule • Interstitial cells produce testosterone • Stem cells are found in the outer surface • There are 2 miotic divisions to produce 4 haploid sperm cells Epididymis • Is an important site for motility and maturation • Duct of the epididymis - • Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm • Nonmotile sperm enter, pass slowly through, and become motile • During ejaculation the epididymis contracts, expelling sperm into the ductus deferens Ductus Deferens and Ejaculatory Duct • Ductus deferens • Propels sperm from the epididymis to the urethra • Vasectomy: cutting and ligating the ductus deferens, which is a nearly 100% effective form of birth control Urethra • Conveys both urine and semen (at different times) • Bibliosecretions clear the acidity from the urine Accessory Glands: Seminal Vesicles • Produces viscous alkaline seminal fluid • Fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins • 70% of the volume of semen • Duct of seminal vesicle joins the ductus deferens to form the ejaculatory duct Accessory Glands: Prostate • Encircles part of the urethra inferior to the bladder • Secretes milky, slightly acid fluid: • Contains citrate, enzymes, and prostate-specific antigen (PSA) – positive indicator of malignancy • Plays a role in the activation of sperm. Similar role of epididymis • Enters the prostatic urethra during ejaculation Accessory Glands: Bulbourethral Glands (Cowper’s Glands) • Pea-sized glands inferior to the prostate • Prior to ejaculation, produce thick, clear mucus • Neutralizes traces of acidic urine in the urethra • Important in survival of sperm Semen • Mixture of sperm and accessory gland secretions • Contains nutrients (fructose), protects and activates sperm, and facilitates their movement (e.g., relaxin – liquifies the semen) • Prostaglandins in semen • Decrease the viscosity of mucus in the cervix (neck of uterus) so the sperm can penetrate into the vagina • Alkalinity neutralizes the acid in the male urethra and female vagina • Antibiotic chemicals destroy certain bacteria • Clotting factors coagulate semen just after ejaculation, then fibrinolysin liquefies it • Only 2–5 ml of semen are ejaculated, containing 20–150 million sperm/ml Spermatogenesis • Sequence of events that produces sperm in the seminiferous tubules of the testes • Most body cells are diploid (2n) and contain • Two sets of chromosomes (one maternal, one paternal) • 23 pairs of homologous chromosomes • Gametes are haploid (n) and contain • 23 chromosomes Meiosis • Gamete formation involves meiosis • Nuclear division in the gonads in which the number of chromosomes is halved (from 2n to n) • Two consecutive cell divisions (meiosis I and II) following one round of DNA replication • Produces four daughter cells/gametes to produce polar bodies. (female – 1 eggs, male- millions of sperm) • Introduces genetic variation – when homolougus pairs line up they *NOTES • EXAM : COMPARE AND CONTRACT MITOSIS AND MEIOSIS**** • S phase occurs in both • Mitosis – chromosomes align on the metaphase line and then they separate. Each pair lined up INDEPENDENTLY of partner*** Normal complement of DNA • Meiosis – produce HAPLOID gametes (half the gamete) so they can be fertilized. Chromosomes STICK with their partner** Means we inherited one chromosome from mother and one from father where they look alleles and code for genes. Genet
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