Transcript Chapter 27
Chapter 27 The Reproductive System G.R. Pitts, J.R. Schiller, and James F. Thompson, Ph.D. The Reproductive Systems Reproductive organs are grouped by function Gonads - testes and ovaries produce gametes and secrete hormones produce gametes and fluid; then discharge into duct system indicates exocrine function production of hormones indicates endocrine function Ducts – receive, store, transport gametes Accessory sex glands – support gametes Supporting structures - various reproductive functions Males Male Reproductive System Testes, a system of ducts, accessory sex glands, and several supporting structures (including the penis) Male Reproductive System Scrotum 2 fibrous sacs which support and protect the testes Muscle cremaster muscle dartos muscle Location and temperature due to muscle contraction sperm production requires temp 3 C below body temp involuntary muscle contraction raises the testes Male Reproductive System Testes - testicles paired oval glands 5 cm x 2.5 cm development influenced by Y sex chromosome and by maternal hormonal levels develop in abdomen begin descent during the 7th month of development Male Reproductive System Surrounded by dense connective tissue covered by tunica vaginalis (serous membrane) from peritoneum internal fibrous capsule = tunica albuginea also forms septa creating lobules 200-300 lobules/testicle tunica albuginea tunica vaginalis Male Reproductive System 3 seminiferous tubules in each lobule (typical) Each seminiferous tubule is lined with spermatogenic cells in various developmental stages Male Reproductive System Blood-Testis Barrier prevents immune system response to sperm antigens Sustentacular (Sertoli) cells create blood-testis barrier with tight junctions respond to FSH and testosterone phagocytize shed excess spermatid cytoplasm control sperm movement and release into the tubule lumen secrete some nutrients for sperm secrete some fluid for sperm transport Male Reproductive System Interstitial endocrinocytes (interstitial cells of Leydig) located between tubules secrete testosterone in response to LH (= ICTH) Spermatogonia undergo meiosis to give rise to spermatazoa Male Reproductive System Spermatogenesis meiosis occurs in the seminiferous tubules produces haploid spermatozoa 64-72 days in humans Spermatogonia Diploid stem cells by mitosis, some remain as viable stem cells through out life others undergo developmental changes to become primary spermatocytes and undergo meiosis Male Reproductive System Reduction division primary spermatocytes undergo meiosis I to become secondary spermatocytes (haploid) secondary spermatocytes undergo meiosis II to become immature spermatids (haploid) Spermatids mature morphologically into spermatozoa = sperm cells spermatid do not separate their cytoplasm completely they maintain cytoplasmic bridges until released into the tubule lumen Male Reproductive System Spermatogenesis spermatids mature physiologically into spermatozoa Requires 10-14 days for migration to and 3-4 days for maturation in the ductus epididymus Older sperms are removed gradually by phagocytes within the epididymus Many sperms are abnormal, either morpholically, physiologically, or genetically 30% abnormal is considered “normal” Male Reproductive System Spermatozoa 300 million/day mature survive about 48 hrs following ejaculation in the female reproductive tract structure head • nuclear material • acrosome - enzymes for penetration into egg midpiece - site of ATP production to power tail tail - flagellum Male Reproductive System Hormones of braintesticular axis anterior pituitary drives changes during puberty controlled by GnRH from hypothalamus begins to secrete FSH, LH LH – targets Interstitial endocrinocytes testosterone dihydrotestosterone (DHT) FSH - Sustentacular cells Androgen-Binding Protein (ABP) concentrates androgens for spermatids Inhibin – negative feedback to the pituitary and hypothalamus Male Reproductive System Development testosterone stimulates pattern development before birth (internal ducts) DHT external genitals estrogens from testes brain development Puberty – testosterone & DHT stimulate enlargement of male sex organs and secondary sexual characteristics Male Reproductive System Testosterone secondary - sex characteristics: muscular, skeletal growth • heavier, thicker muscles and bones in men than in women • also triggers epiphyseal closure pubic, axillary, facial and chest hair oil gland secretion larynx enlargement deepening the voice sexual functions male sexual behavior and aggressive behaviors spermatogenesis sex drive in both male and female metabolism - stimulates protein synthesis “anabolic steroids” are often misused and abused Male Reproductive System Ducts sperm move slowly from the lumen of seminiferous tubules straight tubules rete testis epididymis continuous sperm and testicular fluid production move sperms along fluid contains: H2O, androgens, estrogens, K+, glutamic acid, aspartic acid Male Reproductive System Epididymis posterior border of testes tightly coiled tube - head, body, tail 6 m long if uncoiled pseudostratified columnar epithelium microvilli provide nutrients reabsorb testicular fluid phagocytize degenerating older sperm ductus epididymis site of sperm maturation (10-14 days) - motility may remain in storage for a month, then reabsorbed Male Reproductive System Ductus (vas) deferens less convoluted with a larger diameter ascends, enters pelvic cavity through inguinal canal loops up, over urinary bladder to end in the ampulla Male Reproductive System Ductus (vas) deferens pseudostratified columnar epithelium with thick muscularis transports sperm from epididymis to urethra by peristalsis during ejaculation Male Reproductive System Posterior View Male Reproductive System Spermatic cord: testicular artery, veins, lymphatic vessels, autonomic nerves, vas deferens, cremaster muscle descend with the testes Exit the abdominal cavity through the inguinal canal Vasectomy – a portion of each duct is removed Male Reproductive System Ejaculatory Ducts formed by ducts from seminal vesicle and ductus deferens move sperm into prostatic urethra before ejaculation Male Reproductive System Urethra terminal tract for urinary and reproductive systems 3 regions: prostatic urethra membranous urethra spongy (cavernous) urethra Ends at external urethral orifice at the bulb/glans of the penis Male Reproductive System Accessory sex glands: seminal vesicles, prostate, and bulbourethral glands Male Reproductive System 1) Accessory sex glands secrete the fluid portion of the semen Seminal vesicles base of urinary bladder 60% of semen volume secrete alkaline viscous fluid containing: fructose, ascorbic acid prostaglandins vesiculase (coagulating enzyme) keeps semen near cervix while sperm swim into cervix via flagellar movements Male Reproductive System 2) Prostate below bladder, around urethra secretes milky, slightly acidic fluid with: citrate enzymes • phosphatase • fibrinolysin prostate specific antigen (PSA) 3) Bulbourethral (Cowper's) glands beneath prostate gland at membranous urethra secrete: • • alkaline fluid mucus neutralize acidic urine Male Reproductive System Semen - mixture of sperms and secretions Average volume = 2.5 – 5.0 mL 50-150 million sperm/mL below 20 million/mL infertility Large numbers needed for successful fertilization Slightly alkaline (pH 7.2-7.6), milky and mucoid decreases acidity of vagina fructose is the nutrient for sperm metabolism prostaglandins decrease mucous viscosity and stimulate reverse peristalsis Contains natural antibiotic = seminalplasmin Coagulates after ejaculation into vagina somewhat different mechanism than blood clotting breaks down in 5-20 minutes Male Reproductive System Penis root (attachment) body (shaft) glans penis (head) Male Reproductive System Root of penis - bulb (base of corpus spongiosum) Glans penis with outer corona Terminal slitlike opening (external urethral orifice) Covering is prepuce (foreskin) circumcised in a variety of societies globally Male Reproductive System Body 3 cylindrical tissue masses surrounded by tunica albuginea Dorsolateral pair, the corpora cavernosa penis midventral corpus spongiosum penis with spongy urethra All surrounded by fascia and skin Each section has blood sinuses = erectile tissue Male Reproductive System Erection Arteries dilate with sexual stimulation, a parasympathetic reflex Large quantities of blood enter the sinuses compress superficial veins from sinuses trapped blood erection Close bladder sphincter prevent urine flow prevent semen backflow Ejaculation Sympathetic reflex Peristalsis Arteries constrict, capillary sinuses empty Females Female Reproductive System Ovaries, uterine (Fallopian) tubes, uterus, vagina, vulva, mammary glands Female Reproductive System Ovaries Paired, small (pecan-sized) oval organs in the pelvic cavity Supported by several complex fibrous ligaments Homologous in embryological development to the testes Female Reproductive System Ovary Histology Germinal epithelium Tunica albuginea connective tissue Ovarian follicles Stroma – fibrous connective tissue cortex - outer dense layer with ovarian follicles containing eggs = oocytes medulla - inner loose fibrous connective tissue layer containing blood vessels Female Reproductive System Ovary Histology Germinal epithelium Primordial follicles Ovarian follicles Primary follicles Secondary follicles with antrum formation Vesicular (Graafian) follicles with large antrums After Ovulation: Corpus luteum (“yellow body”) Corpus albicans (“white body”) Female Reproductive System Oogenesis Formation of haploid ova in the ovary Steps Reduction division meiosis I (haploid) Equatorial division meiosis II Maturation – potential for fertilization Female Reproductive System Uterine (Fallopian) tubes = oviducts Extend laterally from uterus to transport ova by peristalsis and cilia-generated current from the ovaries to the uterus Structure (1) infundibulum with fimbriae (2) ampulla (3) isthmus 2 1 3 Female Reproductive System Once a month an ovarian follicle ruptures releasing a secondary oocyte (ovulation) Oocyte drawn into the oviduct by cilia-generated current on the fimbriae and within the tube by cilia and peristalsis Fertilization can occur at any time (ideally in 24 hours) ideally in the ampulla – upper third of oviduct becomes a zygote and then begins mitotic divisions Unfertilized oocytes disintegrate and are swept out Female Reproductive System zygote morula blastocyst with trophoblast membrane implantation more details on the stages of embryonic development in the next chapter Female Reproductive System Uterus Site of menstruation, implantation, fetal development, labor Between the urinary bladder and the rectum Size and shape of an inverted pear Female Reproductive System 3 parts of Uterus 1) Fundus 2) Body with 3) Isthmus fundus body isthmus Female Reproductive System 3 parts of Uterus (cont.) 3) Cervix narrow portion that opens into vagina produces cervical mucus; (20-60 mL/day) • • more receptive to spermatazoa at or near ovulation otherwise the mucus plug keeps microbes out cervix, mucus • • • protect spermatazoa provide nutrients role in capacitation Cervical canal in cervix internal os external os Female Reproductive System Uterus bends between its body and cervix Uterus joins with the vagina at a right angle Female Reproductive System Ligaments provide stability – important especially during labor broad ligaments uterosacral ligaments cardinal ligaments round ligaments Female Reproductive System 3 uterine layers 1) Perimetrium = visceral peritoneum 2) Myometrium 3 layers of smooth muscle • • thickest in fundus thinnest in cervix for expulsion at labor Female Reproductive System 3 uterine layers 3) Endometrium highly vascular surface layer • • simple columnar epithelium ciliated, secretory cells uterine (endometrial) glands Female Reproductive System 3 layers 3) Endometrium stroma (lamina propria) of glandular and connective tissues divided into 2 layers: • • stratum functionalis (functional layer) - shed during menstruation stratum basalis (basal layer) - gives rise to stratum functionalis Female Reproductive System Blood supply from uterine arteries arcuate arteries - circular around the myometrium radial arteries penetrate into the myometrium with smaller branches: spiral straight arterioles • terminate in basilis • supply materials to regenerate functionalis straight spiral arterioles • penetrate functionalis • change during menstruation drained by uterine veins Female Reproductive System Fetal expulsion = labor and delivery Oxytocin and prostaglandins regulate labor ANS controls contractions Female Reproductive System Vagina Tubular, fibromuscular organ with mucous membrane Between bladder, rectum fornix superiorly attached to uterus recess (fornix) forms around the attachment to the cervix Several functions passage for menstrual flow, childbirth receives penis and semen Female Reproductive System Vagina histology Mucosa continuous with the uterus non-keratinized stratified squamous epithelium and connective tissue in folds (rugae) • mucosal cells have large stores of glycogen • upon decomposition produce organic acids lowers pH dendritic (APC) cells – (source for HIV attachment -- AIDS?) Muscularis smooth muscle - outer circular, inner longitudinal layers stretches to receive penis and for accommodating childbirth Adventitia Vaginal - areolar connective tissue orifice - hymen – thin membrane Female Reproductive System Vulva - pudendum Female external genitalia this is a test Mons pubis - anterior, adipose tissue Labia majora lateral skin folds with sebaceous and sudoriferous glands homologous to scrotum Labia minora - medial folds with sebaceous glands Female Reproductive System Clitoris Anterior junction of labia majora Small cylindrical mass of erectile tissue and nerves Plays a role in sexual excitement Homologous to penis; has prepuce and glans Female Reproductive System Vestibule Region between labia minora Mostly the vaginal orifice Bulb of vestibule 2 elongated masses of tissue fill with blood during sexual arousal • narrows vaginal orifice • increases pressure on penis homologous to corpora spongiosum and bulb of penis Female Reproductive System External urethral orifice Anterior to vaginal orifice, posterior to clitoris Exterior opening of the urinary tract Proximity to vagina and anus increase risk of UTI Female Reproductive System Accessory glands Paraurethral (Skene's) glands On either side of external urethral orifice in the vulva Secrete mucus Homologous to prostate gland Greater vestibular (Bartholin's) glands Open in the area between hymen and labia minora Mucus secretion during sexual intercourse Some lesser vestibular mucous glands also present Homologous to bulbourethral (Cowper's) gland General Reproductive System Perineum Diamond shaped area between thighs, buttocks Contains external genitals, anus Urogenital triangle Anal triangle anterior - pubic symphysis posterior coccyx Anterior - urogenital triangle Posterior - anal triangle Episiotomy – to ease labor Female Reproductive System Mammary Glands Modified sudoriferous (sweat) glands that produce milk Anatomy over pectoralis major and serratus anterior muscles attached to the deep fascia surrounded by adipose and fibrous tissue suspensory ligament of breast • runs between skin and deep fascia • supports breast Female Reproductive System Mammary Glands Nipple exterior pigmented projection many closely spaced openings - lactiferous ducts Areola surrounding pigmented area sebaceous (oil) glands Female Reproductive System Mammary Glands 15 - 20 lobes internally separated by adipose tissue (which determines breast size and shape) separated into lobules with milk-secreting glands = alveoli milk (when being produced) passes from alveoli secondary ducts mammary ducts approaching the nipple, the mammary ducts expand to form lactiferous sinuses (for storage) sinuses continue to nipple Female Reproductive System Mammary Develop Gland Development at puberty due to estrogen, progesterone Ducts develop, fat deposition occurs Areola and nipple enlarge; become pigmented Further development occurs following ovulation and corpus luteum formation in menstrual cycle or pregnancy Female Reproductive System Mammary Gland Physiology Primary function is milk synthesis Secretion and ejection together = lactation Primary stimulus for milk production is prolactin from the anterior pituitary Stimuli for milk release (letdown) in response to suckling: oxytocin from posterior pituitary ANS reflexes Female Reproductive System Breast Cancer 12% of women will have breast cancer 3.5% will die of breast cancer Early detection is the most important aspect Each month after a menstrual period, the breasts should be examined for lumps, puckering of skin or nipple retraction or discharge Genes BRCA1 and BRCA2 linked to the 10% of hereditary breast cancers BR-1 is a new marker (2003), esp. for black women But >70% of breast cancers are not associated with known risks http://www.time.com/time/photoessays/breast_cancer/ Female Reproductive System Breast Risk Cancer factors family history early onset menses and late menopause no child or first child after age 34 previous breast cancer exposure to ionizing radiation (x-rays) obesity, alcohol intake, cigarette smoking Detection - mammogram, flattening is the key to a sharp image Treatment lumpectomy (removal of tumor and surrounding tissue) radical mastectomy (breast, pectoral muscles, axillary lymph nodes) Female Reproductive Cycle Two parts in two different areas Ovarian cycle - events in ovary leading to ovulation Menstrual (uterine) cycle - endometrial changes Controlled by varying levels of several hormones from several glands Anterior Pituitary Ovarian follicles Corpus luteum Hormones Ovaries target several organs – Uterus – Breasts – CNS Female Reproductive Cycle - Hormones Female Reproductive Cycle Reproductive cycle Normally 2435 days in length Anterior Pituitary hormones target ovary Ovarian hormones target uterus (and breasts) Female Reproductive Cycle 3 Phases of Reproductive cycle 1. Day 1-4 - menstrual phase 2. Day 5-14 - preovulatory (proliferative) phase 3. Day 15-28 postovulatory (secretory) phase 1. 2. Proliferative 3. Secretory Female Reproductive Cycle Menstrual Phase 50-150 ml of discharge: tissue fluid, mucus, epithelial cells and a small quantity of blood from the endometrium levels of estrogen/progesterone - negative feedback uterine spiral arteries constrict creates ischemic tissue entire stratum functionalis sloughs off Ovaries FSH levels rise (from day 25 of cycle) to stimulate a few primordial follicles to develop into primary follicles All follicles release low levels of estrogen By day four, ~20 develop into primary and then secondary (growing) follicles • granulosa cells surround oocyte • zona pellucida forms between oocyte and the granulosa (follicular cells) – cells secretes watery follicular fluid into antrum – fluid forces oocyte to the follicle’s edge and fills follicular cavity Female Reproductive Cycle Preovulatory Phase - lasts 6-13 days Menstrual and Preovulatory phase together are known as the Follicular phase By day 6 of the cycle, one follicle outgrows others dominant follicle secretes & inhibin estrogen & inhibin reduce FSH secretion • all other follicles stop growing and degenerate = atresia estrogen levels increase due to this single follicle Dominant follicle matures vesicular ovarian (Graafian) follicle (mature follicle) forms a blister-like bulge on the surface of the ovary Female Reproductive Cycle Preovulatory Phase Follicle continues to secrete estrogen FSH is dominant early Close to ovulation, LH becomes important Estrogen stimulates endometrial regrowth stratum basalis • mitosis creates a new stratum functionalis endometrial glands redevelop arterioles coil and lengthen Female Reproductive Cycle Ovulation LH pulse causes rupture of vesicular = Graafian follicle and release of oocyte into the pelvic cavity; occurs approximately day 14 Secondary oocyte surrounded by follicular cells, corona radiata secondary oocyte in metaphase II Fimbriae become more active; cilia create currents in peritoneal fluid to carry oocyte into uterine tube Estrogen causes changes in body temperature and cervical mucus becomes less gelatinous Female Reproductive Cycle Ovulation Prior to ovulation high estrogen exerts positive feedback on FSH, LH sudden surge of LH causes release of oocyte LH surge is measurable Following ovulation follicle collapses becoming corpus hemorrhagicum follicular cells then enlarge, change character, form the corpus luteum follicular cells respond to LH by secreting estrogen and now progesterone Female Reproductive Cycle Postovulatory Phase Most constant in duration, lasts for 14 days, from ovulation to the next menses LH stimulates corpus luteum development (luteal phase); corpus luteum secretes increased levels of estrogen and progesterone Progesterone prepares endometrium to receive an embryo (if it has developed sufficiently) growth and coiling of endometrial glands vascularization of surface endometrium endometrial thickening increased tissue fluid secretory phase for the endometrial glands Female Reproductive Cycle Postovulatory If Phase no fertilization estrogen and progesterone inhibit GnRH and LH corpus luteum degenerates (no LH) corpus albicans levels of estrogen and progesterone • stop endometrial development • stimulate next menstruation • stimulate anterior pituitary hormones to begin next cycle If fertilization occurs corpus luteum maintained until the placenta takes over maintained by hCG (human chorionic gonadotropin) • produced by chorion (outer embryonic membrane which becomes the bulk of the placenta) • home pregnancy test detects hCG placenta produces estrogen, progesterone Female Reproductive Cycle -- Review Female Reproductive Cycle -- Review Physiology of Sexual Intercourse Male Reproductive Act Erection may be initiated by anticipation, memory, visual stimulation or as a reflex from physical stimulation Parasympathetic stimulation causes vasodilation of capillary sinuses, compression of veins erection Lubrication Parasympathetic impulses stimulate bulbourethral and urethral glands glands secrete mucus for lubrication Physiology of Sexual Intercourse Male Reproductive Act (cont.) Orgasm tactile stimulation causes ejaculation • intense stimulation causes rhythmic sympathetic impulses causing peristaltic contractions of ducts propelling spermatazoa into ductus (vas) deferens urethra • simultaneous stimulation of seminal vesicles, prostate and bulbourethral glands add seminal fluid to the spermatazoa • stimulation of skeletal muscle at the base of the penis triggers rhythmic contractions to help expel semen ejaculation sensory input including HR, BP, RR, pleasurable sensations, along with ejaculation, define male orgasm followed by a refractory period Physiology of Sexual Intercourse Female Reproductive Act Arousal – mediated by Parasympathetic Division of ANS stimulation of breasts, genitalia, especially the clitoris, generates arousal clitoris, vaginal mucosa and breasts engorge with blood lubrication - secretion of mucus from epithelium of the cervical mucosa Orgasm (climax) - maximal tactile stimulation of genitalia results in orgasm, mediated by Sympathetic Division (ANS) perineal muscles contract rhythmically; general increase in muscle tension; rhythmic contractions of the uterus engorgement of clitoris, breasts HR, RR, BP intense pleasurable sensations Birth Control = Contraception Sterilization vasectomy in males and tubal ligation in females (tubes cut and sealed) Hormonal methods Intrauterine devices Barrier methods Chemical methods Physiological methods Abortions Birth Control = Contraception Hormonal Oral methods contraception – simulate “pregnant state” generally higher in progesterone and lower in estrogen • negative feedback inhibition of FSH, LH and GnRH • prevents follicular development and ovulation • also alter cervical mucous and make endometrium less receptive to implantation allows for regulation of length of menstrual cycles, menstrual flow, and prevention of ovarian cysts not good for women with clotting problems, cerebral blood vessel damage, hypertension, liver malfunction or heart disease an increased risk for heart attack and stroke in women who smoke and drink Birth Control = Contraception Hormonal methods Norplant surgical implants under skin of progestin prevents ovulation and thickens cervical mucus No male oral contraceptive currently available – research underway Intrauterine Small devices plastic, copper or stainless steel device inserted into uterine cavity to prevent implantation Danger of pelvic inflammatory disease, infertility, and excessive menstrual bleeding and pain Birth Control = Contraception Barrier methods Condom nonporous materials (e.g., latex) provide mechanical barrier to sperm deposition reliable when used correctly both male and female versions The only method likely to prevent STD's and reliable when used correctly Diaphragm rubber dome-shaped device is placed over cervix to stop sperm passage; often used with spermicide toxic shock syndrome and frequent urinary tract infections are possible with incorrect use Birth Control = Contraception Chemical methods - spermicidal agents, make vagina more inhospitable to sperm and may prevent sperm flagellar motility Physiological Coitus methods – not too reliable interruptus (withdrawal) Rhythm method - abstention for 3 days before and after ovulation (estimated) Sympto-thermal method - abstention when signs of ovulation are present Birth Control = Contraception Induced RU486 abortion (mifepristone) – drug blocks progesterone preventing proper endometrial development menstruation occurs Various surgical procedures End Chapter 27