Reproductive System PDF

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Lecture notes on Reproductive System Dr. Cameron Sheeler...

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Concepts that will cover Male reproductive system Female reproductive system Hormones involved with reproduction Ovulation and uterine cycle Gametogenesis

The Male Reproductive System Delivers Sperm  Testes produce sperm – Scrotum: sac of skin and smooth muscle that holds the testes – Maintains testes at a slightly lower temperature – Seminiferous tubules within testes: produce sperm  Epididymis and ductus deferens: sperm become motile and are stored here  Ductus deferens: transports sperm to where it becomes the ejaculatory duct  Route of sperm through male reproductive structures – Seminiferous tubules – Epididymis – Ductus deferens – Ejaculatory duct – Penis Accessory Glands Help Sperm Survive  Semen: mixture of sperm and secretions of accessory glands  Seminal vesicles – Secrete fructose (provides source of energy for sperm) and produce/secrete most of the seminal fluid  Prostate gland – Secretes watery alkaline fluid to raise vaginal pH  Bulbourethral gland – Secretes lubricating mucus – Cleanses urethra Sperm Production Requires Several Cell Divisions  Several cell divisions (mitosis and meiosis) in seminiferous tubules produce sperm  Cell divisions produce a large number of sperm with half the number of chromosomes of somatic cells (haploid)  Sperm (and eggs) are referred to as gametes and are haploid  Sequence of cell types, leading to sperm – Spermatogonia (2n), primary spermatocyte (2n), secondary spermatocyte (n), spermatids (n), sperm (n)  Sertoli cells provide support, nourishment Testosterone Affects Male Reproductive Capacity  Testosterone

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– Steroid hormone produced by interstitial cells in testes (between seminiferous tubules) – Function: – Controls growth and function of male reproductive tissues – Stimulates aggression and sexual behavior – Controls development of secondary sexual characteristics – Determines rate of sperm formation Hormones that regulate testosterone and sperm production – Gonadotropin-releasing hormone (GnRH) from hypothalamus stimulates release of LH and FSH – LH (from anterior pituitary) stimulates production of testosterone – FSH (from anterior pituitary) may enhance sperm formation with Sertoli cells – Inhibin: produced by Sertoli cells, inhibits secretion of FSH Negative feedback loop maintains constant blood concentration of testosterone

The Female Reproductive System Produces Eggs and Supports Pregnancy  Ovaries – Release oocytes (immature eggs) and secrete the hormones estrogen and progesterone  Oviduct (Fallopian tube) – Leads from the ovary to the uterus – Fertilization occurs in the upper third of the oviduct – Three to four day trip through oviduct to uterus  Ovaries – Release oocytes (immature eggs) and secrete the hormones estrogen and progesterone  Oviduct (Fallopian tube) – Leads from the ovary to the uterus – Fertilization occurs in the upper third of the oviduct – Three to four day trip through oviduct to uterus  Vagina – Organ of sexual intercourse and birth canal  External genitalia – Labia majora and minora – Clitoris Mammary Glands Nourish the Infant  Breasts contain mammary glands  Mammary glands are modified sweat glands, part of the integumentary system  Specialized for lactation (production of milk)  Hormonal control of lactation: – Prolactin (anterior pituitary hormone)—stimulates milk production

– Oxytocin (posterior pituitary hormone)—stimulates contractions that eject milk

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Menstrual Cycle Consists of Ovarian and Uterine Cycles

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Pattern of changes, which cycles every 28 days Controlled by hormones of pituitary gland and ovaries Begins at puberty and continues until menopause, except during pregnancy

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Consists of two linked cycles – Ovarian cycle – Series of changes in ovaries associated with oocyte maturation – Controlled by FSH and LH – Uterine cycle – Changes in the endometrial lining of the uterus – Controlled by estrogen and progesterone Ovarian Cycle: Oocytes Mature and Are Released Immature follicle of primary oocyte and granulosa cell develops; FSH and LH increase Granulosa cells divide and produce zona pellucida around oocyte Antrum develops within follicle; some estrogen and progesterone are secreted Secondary oocyte and polar body are produced; follicle matures (Graafian follicle) Increasing estrogen causes surge of LH; ovulation occurs Corpus luteum formed from follicle; large amounts of estrogen and progesterone are secreted If fertilization and pregnancy occurs  Chorion (embryonic tissue) secretes human chorionic gonadotropin (hCG)  hCG is detected by pregnancy tests  hCG causes corpus luteum to continue to produce estrogen and progesterone for another 9–10 weeks  After 9–10 weeks, the placenta takes over progesterone and estrogen production  High levels of estrogen and progesterone prevent ovulation during pregnancy Uterine Cycle Prepares the Uterus for Pregnancy Series of changes that occur in endometrium as it prepares for the possible arrival of a fertilized egg Menstrual phase – Days 1–5 – Estrogen and progesterone decrease

– Endometrial lining degenerates – Menstruation occurs  Proliferative phase – Days 6–14 – Estrogen and progesterone increase – Endometrial lining proliferates  Ovulation – Day 14  Secretory phase – Days 15–28 – Corpus luteum produces progesterone and estrogen – Endometrium continues to proliferate – Uterine glands mature – Uterus is prepared to accept and nourish a fertilized egg – Cyclic Changes in Hormone Levels Produce the Menstrual Cycle Cycles of hormones of pituitary and reproductive structures – Positive feedback – In proliferative phase, increasing estrogen causes surge in LH, which in turn causes ovulation – Negative feedback – In secretory phase, steady levels of estrogen and progesterone inhibit LH and FSH release Human Sexual Response, Intercourse, and Fertilization  Human sexual response – Excitement: increased sexual awareness and arousal – Plateau: intense and continuing arousal – Orgasm: peak of sexual sensations – Resolution: abatement of arousal – Male sexual response: orgasm, marked by ejaculation, refractory period – Female sexual response: orgasm, marked by rhythmic muscular contractions 

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Fertilization: One Sperm Penetrates the Egg Fertilization – Ejaculate: may contain several hundred million sperm – Sperm may reach egg within hours to a day or more – One sperm penetrates egg within the oviduct – Sperm may be viable for up to 5 days within the female reproductive tract Birth Control Methods: Controlling Fertility

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Abstinence: not having intercourse Surgical sterilization – Vasectomy in males: cut and tie off both ductus deferens – Tubal ligation in females: cut and tie off both oviducts Hysteroscopy in females: cauterize the oviducts to seal them Birth Control Methods: Pills, Injections, Patches, and Rings Birth control pills (oral contraceptives) – Combination of synthetic progesterone and estrogen – Inhibit release of FSH and LH Hormone injections – Depo-Provera (lasts 3 months) Hormone patch – Ortho Evra Vaginal ring – NuvaRing Implant – Implanon and Nexplanon; progesterone-containing rod under skin

Block – – –

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Birth Control Methods: Hormonal Methods: Pills, Injections, Patches, and Rings ovulation—quite effective Advantages: – May reduce cramps and menstrual flow – Some protection against ovarian and uterine cancers Disadvantages: – Side effects include acne, headaches, fluid retention, high blood pressure, blood clots Do not protect against sexually transmitted diseases (STDs)

Other Birth Control Methods IUDs: Intrauterine devices – Small plastic or metal piece inserted into uterus – Create mild chronic inflammation that prevents fertilization or implantation – Mirena: includes progesterone-like drug Diaphragms and cervical caps – Prevent sperm from entering the cervix – Effectiveness improved when used with spermicides Chemical spermicides – Kill sperm cells Condoms – Trap ejaculated sperm Natural alternatives

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– Rhythm method, withdrawal After intercourse pills – Ella  Single pill, within five days after intercourse  Prevents ovulation or implantation – Plan B (morning after pill) – Mifeprex (RU-486)  Prevents implantation of pre-embryo  Causes regression of endometrial lining  May be prescribed to induce an early abortion, up to seven weeks after becoming pregnant Elective Abortion Methods: – Mifiprex can be used up to seven weeks after pregnancy onset – Vacuum suctioning of uterus – Surgical scraping of uterine lining – Infusion of strong saline solution The Future in Birth Control Currently in research and development: – Male birth control: reduces sperm production – Vaccines for women – Vaccine against hCG (human chorionic gonadotropin) – Vaccine against sperm

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Infertility: Inability to Conceive Infertility: inability to achieve pregnancy after a year of trying Many causes of infertility – Number and quality of sperm – Less than 60 million/ejaculation is considered infertile – Pelvic inflammatory disease (PID) – Scarred, blocked oviducts

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Enhancing Fertility Artificial insemination

causes of infertility (continued) Abnormal production of FSH and/or LH Irregular menstrual cycles Endometriosis Strongly acidic vaginal secretions Decreased reproductive capacity with age Miscarriage (spontaneous abortion)

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Artificial reproductive technologies (ARTs) – Both sperm and eggs are handled outside of the body – Method of choice for women with blocked or damaged oviducts – Immature eggs must first be harvested from a woman – Once eggs are harvested, there are a variety of different techniques

In vitro fertilization (IVF) – Fertilization in test tube outside of the body – After several cell divisions, embryo is inserted into the uterus via the vagina  GIFT (gamete intrafallopian transfer) – Unfertilized eggs and sperm placed directly in oviduct  ZIFT (zygote intrafallopian transfer) – Fertilized egg is placed in oviduct  Fertility-enhancing drugs – Boost production of developing eggs – May result in multiple births  Surrogate motherhood Sexually Transmitted Diseases (STDs)  Transmitted by sexual contact, including – Genital, oral-genital, anal-genital  Can be very damaging or deadly  May affect organs outside of the reproductive system  Some are not treatable  Infectious agents include viruses, bacteria, protozoa, fungi, and arthropods Bacterial STDs: Syphilis  Caused by bacteria Treponema pallidum  Three phases – Primary: lesion in genital area – Secondary: rash – Bacteria invades blood, lymph nodes, nervous system, bones – Tertiary: widespread damage to nervous system and cardiovascular system  Congenital syphilis: transmitted by infected mother to fetus  Treatment: penicillin Bacterial STDs: Gonorrhea  Caused by bacteria Neisseria gonorrhoeae  Male symptoms: penile discharge, painful urination  Female symptoms: vaginal discharge, burning sensation when urinating – Females are often asymptomatic  Can be passed to newborn during birth, causing a serious eye infection  If untreated, can lead to inflammation, scarring, and infertility 

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Usually can be treated with antibiotics

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Bacterial STDs: Chlamydia Caused by bacteria Chlamydia trachomatis Often goes undiagnosed due to mildness of symptoms – Men: penile discharge, burning upon urination – Women: vaginal discharge, burning and itching sensation If untreated, may lead to pelvic inflammatory disease in women Can infect newborn during birth Treatment: antibiotics

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Viral STDs: HIV and Hepatitis B HIV: one of the most dangerous STDs – Slowly destroys the immune system, causing AIDS (acquired immunodeficiency syndrome) – Treatment may achieve remission, but no cure Hepatitis B virus – More contagious than HIV, but not as deadly – Affects liver – Vaccine available for prevention Viral STDs: Genital Herpes and Human Papillomavirus (HPV) Genital herpes: Herpes simplex virus – Painful blisters may recur periodically – Drugs will suppress outbreaks and contagious phase, but no cure – May infect infants during birth Human papillomavirus (HPV) – Many strains can cause warts in genital area – Two types cause cervical cancer – Vaccines to prevent cervical cancer: Gardasil, Cervarix – CDC recommends that all children (girls and boys) be vaccinated at age 11 or 12 (before first sexual contact) Other STDs: Yeast Infections Candida albicans (yeast): normally present but may overgrow – Pain, inflammation, discharge – Can be passed sexually – May follow antibiotic treatment for bacterial infections – Treatment: topical or oral antifungal medication Other STDs: Trichomoniasis Trichomoniasis: caused by protozoan Trichomonas vaginalis – Women: – Vaginitis—inflammation of vagina – Frothy foul-smelling discharge – Men: – Inflammation of penis, discharge

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Other STDs: Pubic Lice Tiny arthropod, related to spiders Commonly called “crabs” Prefer to live on pubic hair Cause intense itching and skin irritation Treatment: anti-lice medication Clothes and bedding should be thoroughly washed in hot water

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Protecting Yourself Against STDs Choose partner wisely Communicate Use suitable barriers Get tested and treated Get vaccinated (Hepatitis B and HPV)...