Introduction to Reproductive Systems - Physiology and Anatomy - Lecture Slides, Slides of Physiology

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Chapter 28 The Reproductive Systems • Sexual reproduction produces new individuals – germ cells called gametes (sperm & 2nd oocyte) – fertilization produces one cell with one set of chromosomes from each parent • Gonads produce gametes & secrete sex hormones • Reproductive systems – gonads, ducts, glands & supporting structures – Gynecology is study of female reproductive system – Urology is study of urinary system & male reproductive system Docsity.com Chromosomes in Somatic Cells & Gametes • Somatic cells (diploid cells) – 23 pairs of chromosomes for a total of 46 • each pair is homologous since contain similar genes in same order • one member of each pair is from each parent – 22 autosomes & 1 pair of sex chromosomes • sex chromosomes are either X or Y • females have two X chromosomes • males have an X and a smaller Y chromosome • Gametes (haploid cells) – single set of chromosomes for a total of 23 – produced by special type of division: meiosis Docsity.com Meiosis II • Consists of 4 phases : prophase II, metaphase II, anaphase II and telophase II • Similar steps in this cellular process as in mitosis – centromeres split – sister chromatids separate and move toward opposite poles of the cell • Each of the daughter cells produced by meiosis I divides during meiosis II and the net result is 4 genetically unique haploid cells or gametes. Docsity.com Male Reproductive System • Gonads, ducts, sex glands & supporting structures • Semen contains sperm plus glandular secretions Docsity.com Scrotum • Sac of loose skin, fascia & smooth muscle divided into two pouches by septum • Skin contains dartos muscle causes wrinkling • Temperature regulation of testes – sperm survival requires 3 degrees lower temperature than core body temperature – cremaster muscle in spermatic cord • elevates testes on exposure to cold & during arousal • warmth reverses the process Docsity.com Tunica Vaginalis • Piece of peritoneum that descended with testes into scrotal sac. • Allows for easier movement of testes within scrotum Docsity.com Cryptorchidism • Testes do not descend into the scrotum • 3% of full-term & 30% of premature infants • Untreated bilateral cryptorchidism results in sterility & a greater risk of testicular cancer • Descend spontaneously 80% of time during the first year of life – surgical treatment necessary before 18 months Docsity.com Formation of Sperm Spermatogenesis is formation of sperm cells from spermatogonia. Docsity.com Spermatogenesis • Secondary spermatocytes are formed – 23 chromosomes of which each is 2 chromatids joined by centromere – goes through meiosis II • 4 spermatids are formed – each is haploid & unique – accounts for synchronized release of sperm that are 50% X chromosome & 50% Y chromosome Docsity.com Sperm Morphology • Adapted for reaching & penetrating a secondary oocyte • Head contains DNA & acrosome (hyaluronidase and proteinase enzymes) • Midpiece contains mitochondria to form ATP • Tail is flagellum used for locomotion Docsity.com Hormonal Control of Spermatogenesis • Puberty – hypothalamus increases its stimulation of anterior pituitary with releasing hormones – anterior pituitary increases secretion LH & FSH • LH stimulates Leydig cells to secrete testosterone – an enzyme in prostate & seminal vesicles converts testosterone into dihydrotestosterone (DHT-more potent) • FSH stimulates spermatogenesis – testosterone stimulates final steps spermatogenesis Docsity.com Pathway of Sperm Flow through the Ducts of the Testis • Seminiferous tubules • Straight tubules • Rete testis • Efferent ducts • Ductus epididymis • Ductus (vas) deferens Docsity.com Epididymis • Comma-shaped organ, 1.5in long along posterior border of each testis • Head, body and tail region • Tail region continues as ductus deferens Docsity.com Ductus (Vas) Deferens • Pathway of 18 inch muscular tube – ascends along posterior border of epididymis – passes up through spermatic cord and inguinal ligament – reaches posterior surface of urinary bladder – empties into prostatic urethra with seminal vesicle • Lined with pseudostratified columnar epithelium & covered with heavy coating of muscle – convey sperm along through peristaltic contractions – stored sperm remain viable for several months Docsity.com Inguinal Canal & Inguinal Hernias • Inguinal canal is 2 inch long tunnel passing through the 3 muscles of the anterior abdominal wall -- weakens wall – originates at deep inguinal ring and ends at superficial ring • Indirect hernia -- loop of intestine protruding through deep ring • Direct hernia -- loop of intestine pushes through posterior wall of inguinal canal • More common in males Docsity.com Ejaculatory Ducts • Formed from duct of seminal vesicle & ampulla of vas deferens • About 1 inch long • Adds fluid to prostatic urethra just before ejaculation Docsity.com Urethra • 8 inch long passageway for urine & semen • Prostatic urethra (1 inch long) • Membranous urethra (passes through UG diaphragm ) • Penile (spongy) urethra (through corpus spongiosum) Docsity.com Bulbourethral or Cowper’s Gland • Paired, pea-sized gland within the UG diaphragm • Secretes alkaline mucous into spongy urethra • Neutralizes acids and lubricates Docsity.com Semen • Mixture of sperm & seminal fluid – glandular secretions and fluid of seminiferous tubules – slightly alkaline, milky appearance, sticky • Typical ejaculate is 2.5 to 5 ml in volume • Normal sperm count is 50 to 150 million/ml – actions of many are needed for one to enter • Semen analysis----bad news if show lack of forward motility, low count or abnormal shapes Docsity.com Penis • Passageway for semen & urine • Body composed of three erectile tissue masses filled with blood sinuses • Composed of bulb, crura, body & glans penis Docsity.com Circumcision • Removal of prepuce • 3 - 4 days after birth • Possibly lowers UTIs, cancer & sexually transmitted disease Docsity.com Female Reproductive System • Ovaries produce 2nd oocytes & hormones • Uterine tubes transport fertilized ova • Uterus where fetal development occurs • Vagina & external genitalia constitute the vulva • Mammary glands produce milk Docsity.com The Ovary • Pair of organs, size of unshelled almonds found in upper pelvic region • Regional histology – tunica albuginea is capsule of dense connective tissue – cortex is region just deep to tunica, contains follicles – medulla is deeper region composed of connective tissue, blood vessels & lymphatics – germinal epithelium is simple epithelial covering over the ovary Docsity.com Life History of Oogonia • Germ cells from yolk sac migrate to ovary & become oogonia • As a fetus, oogonia divide to produce millions by mitosis but most degenerate (atresia) • Some develop into primary oocytes & stop in prophase stage of meiosis I – 200,000 to 2 million present at birth – 40,000 remain at puberty but only 400 mature during a woman’s life • Each month, hormones cause meiosis I to resume in several follicles so that meiosis II is reached by ovulation • Penetration by the sperm causes the final stages of meiosis to occur Docsity.com Uterine or Fallopian Tubes • Narrow, 4 inch tube extends from ovary to uterus – infundibulum is open, funnel-shaped portion near the ovary • fimbriae are moving finger-like processes – ampulla is central region of tube – isthmus is narrowest portion joins uterus Docsity.com Function of Uterine Tube • Function -- events occurring in the uterine tube – fimbriae sweep oocyte into tube, cilia & peristalsis move it along, sperm reaches oocyte in ampulla, fertilization occurs within 24 hours after ovulation & zygote reaches uterus about 7 days after ovulation Docsity.com Blood Supply to the Uterus • Uterine arteries branch as arcuate arteries and radial arteries that supply the myometrium • Straight & spiral branches penetrate to the endometrium – spiral arteries supply the stratum functionalis – their constriction due to hormonal changes starts menstrual cycle Docsity.com Hysterectomy • Surgical removal of the uterus • Indications for surgery – endometriosis, ovarian cysts, excessive bleeding, cancer of cervix, uterus or ovaries • Complete hysterectomy removes cervix • Radical hysterectomy removes uterus, tubes, ovaries, part of vagina, pelvic lymph nodes and supporting ligaments Docsity.com Vagina • Passageway for birth, menstrual flow & intercourse • Description – 4 inch long fibromuscular organ ending at cervix • mucosal layer – stratified squamous epithelium & areolar connective tissue – large stores of glycogen breakdown to produce acidic pH • muscularis layer is smooth muscle allows considerable stretch – lies between urinary bladder and rectum – orifice partially closed with membrane (hymen) Docsity.com Mammary Glands • Modified sweat glands that produce milk (lactation) – amount of adipose determines size of breast – milk-secreting glands open by lactiferous ducts at the nipple – areola is pigmented area around nipple – suspensory ligaments suspend breast from deep fascia of pectoral muscles (aging & Cooper’s droop) Docsity.com Fibrocystic Disease of the Breasts • Most common cause of breast lumps • Cysts and thickenings of alveoli develop • Cause – hormonal imbalance • excess of estrogen or deficiency of progesterone in the postovulatory phase – result is lumpy, swollen & tender breast a week before menstruation begins Docsity.com Female Reproductive Cycle • Controlled by monthly hormone cycle of anterior pituitary, hypothalamus & ovary • Monthly cycle of changes in ovary and uterus • Ovarian cycle – changes in ovary during & after maturation of oocyte • Uterine cycle – preparation of uterus to receive fertilized ovum – if implantation does not occur, the stratum functionalis is shed during menstruation Docsity.com Preovulatory Phase • Lasts from day 6 to 13 (most variable timeline) • In the ovary (follicular phase) – follicular secretion of estrogen & inhibin has slowed the secretion of FSH – dominant follicles survives to day 6 – by day 14, graafian follicle has enlarged & bulges at surface – increasing estrogen levels trigger the secretion of LH • In the uterus (proliferative phase) – increasing estrogen levels have repaired & thickened the stratum functionalis to 4-10 mm in thickness Docsity.com Ovulation • Rupture of follicle & release of 2nd oocyte on day 14 • Cause – increasing levels of estrogen stimulate release of GnRH which stimulates anterior pituitary to release more LH Docsity.com Signs of Ovulation • Increase in basal body temperature • Changes in cervical mucus • Cervix softens • Mittelschmerz---pain Docsity.com Human Sexual Intercourse • 4 phases – excitement phase produced by parasympathetic NS • engorgement of blood vessels & cardiovascular changes – plateau phase of variable duration • sexual flush to face & chest – orgasm phase (climax) • rhythmical muscular contractions & pleasure • sympathetic nervous system causes ejaculation – resolution • profound relaxation & return to normal • male refractory period where 2nd ejaculation is impossible • Some male & female physiological differences Docsity.com Erectile Dysfunction (Impotence) • Consistent inability of adult male to hold an erection long enough for sexual intercourse • Causes – psychological or emotional factors – physical factors • diabetes mellitus, vascular disturbances, neurological disturbances, testosterone deficiency, drugs (alcohol, nicotine, antidepressants, tranquilizers,etc) • Viagra causes vasodilation of penile arteries and brings on an erection Docsity.com Birth Control Methods • Surgical • Hormonal • Mechanical barriers • Periodic abstinence • Coitus interruptus • Induced abortion Docsity.com Other Hormonal Methods • Norplant – surgically implanted capsules releasing progestin & inhibiting ovulation for 5 years • Depo-provera – intramuscular injection of progesterone every 3 months that changes uterine lining & ovum maturation • Vaginal ring – worn internally releasing progestin or combination of progestin & estrogen Docsity.com Intrauterine Devices • Small object made of plastic, copper or steel left in cavity of uterus – changes uterine lining so is unfavorable for embryo implantation – approved for 10 year usage • May cause excessive bleeding or discomfort Docsity.com Spermatocides • Chemical substances in foam, cream, jelly, douche or suppository that kill sperm upon contact • Available without prescription • Normally used in conjunction with a barrier device • May inactivate HIV virus & decrease incidence of gonorrhea Docsity.com Induced Abortion • Miscarriage is a spontaneous loss of the fetus • Induced abortions – vacuum aspiration (suction) – infusion of saline solution to kill embryo – surgical evacuation (scraping) • `RU 486 is called a nonsurgical abortion – antiprogestin drug that causes uterine lining to collapse & embryo is lost (menstruation occurs) – can be taken up to 5 weeks after conception Docsity.com Early Anatomy -- Male Pattern • Depends upon SRY gene on Y chromosome – sertoli cells secrete Mullerian inhibiting substance – leydig cells secrete testosterone causing mesonephric duct to develop into male tubes • seminiferous tubules, epididymis & vas deferens & seminal vesicles • prostate & cowper’s glands are outgrowths of urethra – testosterone secretion stops at birth when hCG from the placenta stops stimulating leydig cells Docsity.com Early Anatomy -- Female Pattern • Females have 2 X chromosomes so SRY gene is absent • Gonads develop into ovaries – no mullerian-inhibiting substance is produced so female pattern of duct development occurs – paramesonephric duct develops into vagina, uterus & uterine tubes – mesonephric ducts degenerate • Female pattern depends on the absence of testosterone Docsity.com Aging Female Reproductive System • Hormone-directed sexual characteristics start to develop at puberty • Reproductive cycle occurs once/month from menarche (10-14) until menopause (between 40 & 50) • Fertility declines with age – decreasing number of viable follicles – less frequent ovulation – declining ability of uterus to support young embryo • Menopause is cessation of menstruation – no remaining follicles to stimulate estrogen secretion – osteoporosis, hot flashes, mood swings, organ atrophy Docsity.com Aging Male Reproductive System • Decline in reproductive function is more subtle (capacity may remain into 90’s) • Decline in testosterone at 55 – reduced muscle synthesis – fewer viable sperm – reduced sexual desire • Enlargement of prostate (benign hyperplasia) – 1/3 of males over 60 – frequent urination, decreased force of stream, bed- wetting & sensation of incomplete emptying Docsity.com Sexually Transmitted Disease • On the increase in the United States • Chlamydia -- bacteria; asymptomatic, leads to sterility from scar tissue formation • Gonorrhea -- bacteria, discharge common, blindness if newborn is infected during delivery • Syphilis -- bacteria, painless sores (chancre), 2nd stage all organs involved, 3rd stage organ degeneration is apparent (neurosyphilis) • Genital Herpes -- virus, incurable, painful blisters • AIDS & hepatitis B --viruses (chapters 22 & 24) Docsity.com Premenstrual Syndrome (PMS) • Physical & emotional distress during the postovulatory (luteal) phase – disappear at onset of menstruation • Signs & symptoms are variable – mood swings, depression, headache, fatigue, backache, constipation, breast tenderness, edema • Since occurs only after ovulation, oral contraceptives are an effective treatment – careful diet & exercise may help Docsity.com Endometriosis • Growth of endometrial tissue outside of the uterus – tissue discharged from open-end of uterine tubes during menstruation – can cover ovaries, outer surface of uterus, colon, kidneys and bladder • Problem is tissue responds to hormonal changes by proliferating then breaking down & bleeding – causes pain, scarring & infertility Docsity.com Breast Cancer • Second-leading cause of cancer death in the U.S. – 1 in 8 women affected – rarely before 30, but more common after menopause • 5% of cases are younger women (genetic mutation) • Detection by self-examination & mammography – ultrasound determines if lump is benign, fluid-filled cyst or solid & possibly malignant • Risk factors – family history, no children, radiation, alcohol & smoking • Treatment – lumpectomy, radical mastectomy, radiation therapy or chemotherapy Docsity.com