Unit 3 SG Ch 24 PDF: Reproductive Systems - Exam Study Guide

CHAPTER 24 –Structure & Function of the Reproductive systems What occurs with the fetus at each week of gestation? Initially in embryonic development, the reproductive structures of male and female embryos are homologous (the same) and consist of one pair of primary sex organs, or gonads, and two p...

CHAPTER 24 –Structure & Function of the Reproductive systems What occurs with the fetus at each week of gestation? Initially in embryonic development, the reproductive structures of male and female embryos are homologous (the same) and consist of one pair of primary sex organs, or gonads, and two pairs of ducts, the mesonephric ducts (wolffian ducts) and the paramesonephric ducts (müllerian ducts). Both pairs of ducts empty into an opening called the urogenital sinus. Internal Structures: The first sign of development of reproductive organs (male or female) occurs during the fifth week of gestation. Between 6 and 7 weeks of gestation à male embryo will differentiate under the influence of testes- determining factor (a protein expressed by a gene in the sex-determining region on the Y chromosome) When the SRY gene is expressed à male gonadal development prevails. TDF stimulates the male gonads to develop into the two testes and by 8 weeks of gestation testosterone secretion begins. By 9 months’ gestation, the male gonads (testes) have descended into the scrotum. The testes produce sperm after puberty Female gonadal development à in the absence of SRY expression and with the expression of other genes. The presence of estrogen and the absence of testosterone cause regression of the wolffian system 6 to 8 weeks’ gestation, the two female gonads develop into ovaries, which will produce ova By the 10th week of gestation, the loss of wolffian ducts allows the müllerian ducts to join and become the uterus, fallopian tubes, cervix, and upper two thirds of the vagina External Structures: During the first 7 to 8 weeks of gestation, both male and female embryos develop an elevated structure called the genital tubercle. Testosterone is necessary for the genital tubercle to differentiate into male genitalia; otherwise, female genitalia develop, which may occur even in the absence of ovaries possibly because of the presence of placental estrogens. Hormone Production: Anterior pituitary gland development starts between the 4th and 6th weeks of fetal life, and the vascular connection between the hypothalamus and the pituitary is established by the 12th week Gonadotropin-releasing hormone (GnRH) is produced in the hypothalamus by 10 weeks gestation and controls the production of two gonadotropins by the anterior pituitary gland, luteinizing hormone (LH) and follicle-stimulating hormone (FSH) In the female fetus, high levels of FSH and LH are excreted. o FSH and LH stimulate the production of estrogen and progesterone by the ovary. The production of FSH and LH rises until about 28 weeks gestation, until the production of estrogen and progesterone by the ovaries and placenta is high enough to result in the decline of gonadotropin production. o Production of primitive female gametes (ova) occurs solely during fetal life. 1 Know the different parts of the female GU system and the function of each. The function of the reproductive system is to produce mature ova If fertilization occurs à the female reproductive system provides protection and nourishment of the fetus until it is expelled at birth The most important internal reproductive organs in females are the ovaries, fallopian tubes, uterus, and vagina. External Genitalia: 1. Mons pubis (mons veneris): a. fatty layer of tissue over the pubic symphysis b. during puberty it becomes covered in hair and sebaceous and sweat glands become more active. c. Estrogen causes it to become a mound like shape. Labia swell with blood during sexual arousal 1. Labia majora (labium majus): two folds of skin arising at the mons pubis and extending back to the fourchette, forming a cleft. Highly sensitive to temperature, touch, pressure, and pain; it is homologous to the male scrotum, and it protects the inner structures of the vulva. 2. Labia minora (labium minus): two smaller, thinner, asymmetric folds of skin within the labia majora that form the clitoral hood and frenulum à split to enclose the vestibule and converge near the anus to form the fourchette; hairless, pink, and moist and are well supplied with nerves, blood vessels, and sebaceous glands (secrete a bactericidal fluid that has a distinctive odor and lubricates and waterproofs the vulvar skin) 3. Clitoris: richly innervated, erectile organ between the labia minora; small, cylindrical structure having a visible glans and a shaft that lie beneath the skin; homologous to the male penis; secretes smegma (unique odor that may be sexually arousing to the male) Clitoris is a major site of sexual stimulation and orgasm; sexual arousal à erectile tissues in the clitoris fill with blood, causing it to enlarge slightly. 4. Vestibule: an area protected by the labia minora and contains the external opening of the vagina (introitus or vaginal orifice); a thin, perforated membrane called the hymen may cover the introitus; also contains the opening to the urethra or urinary meatus. a. Structures are lubricated by two pairs of glands: b. Skene glands: open on both sides of the urinary meatus à lubricate the urinary meatus and the vestibule c. Bartholin glands: open on either side of the introitus à secrete mucous à lubricates the inner labial surfaces and enhances the viability / motility of sperm. 5. **Secretions from both sets of glands facilitate coitus: sexual excitement à highly vascular tissue just beneath the vestibule fills with blood and becomes engorged. 6. Perineum: less hair, skin, and subcutaneous tissue lying beneath the vaginal orifice and anus; has little subcutaneous fat (skin is close to underlying muscles); covers the muscular perineal body (fibrous structure that consists of elastic fibers and connective tissue, and serves as the common attachment for the bulbocavernosus, the external anal sphincter, and the levator ani muscles) a. Varies in length (2-5cm or more); the length of the perineum and the elasticity of the perineal body influences tissue resistance and injury during childbirth. 2 Internal Genitalia: 1. Vagina: an elastic fibromuscular canal (9 to 10 cm long in a reproductive-aged female); lies between the urethra (and part of the bladder) and the rectum. Mucosal secretions from the upper genital organs, menstrual fluids, and products of conception leave the body through the vagina, which also receives the penis during coitus. a. The vaginal wall is composed of four layers: 1. Mucous membrane lining of squamous epithelial cells that thickens and thins in response to hormones, particularly estrogen. The squamous epithelial membrane is continuous with the membrane that covers the lower part of the uterus. In women of reproductive age, the mucosal layer is arranged in transverse wrinkles or folds, called rugae (singular, ruga) that permit stretching during coitus and childbirth 2. Fibrous connective tissue containing numerous blood and lymphatic vessels 3. Smooth muscle 4. Connective tissue and rick network of blood vessels b. Upper part of vagina à surrounds cervix (lower end of the uterus) i. The recessed space around the cervix is called the fornix of the vagina à a pouch called the cul-de-sac separates the posterior fornix and the rectum. c. During sexual arousal the vaginal wall becomes engorged with blood à pushes some fluid to the surface of the mucosa à enhancing lubrication. d. Two factors help maintain the self-cleansing action of the vagina and defend it from infection: § Acid-base balance: discourages the proliferation of most pathogenic bacteria § Thickness of the vaginal epithelium. At puberty the pH is more acidic (4-5) and the squamous epithelial lining thickens. Protection from infection is greatest during the years when a woman is most likely to be sexually active. Both defenses are greatest when estrogen levels are high, and the vagina contains a normal population of lactobacillus acidophilus § Any condition that causes the vaginal pH to rise (i.e. douching or use of vaginal sprays or deodorants, presence of low estrogen levels, destruction of L. acidophilous by antibiotics à lowers vaginal defenses against infection) 2. Uterus: hollow pear-shaped organ whose lower end opens into the vagina. Anchors and protects a fertilized ovum, provides an optimal environment while the ovum develops, and expels the fetus at birth. a. During sexual excitement the opening of the uterus (cervix) dilates slightly, uterus increases in size and moves upward and backward, resulting in cervix “sitting” in a pool of semen. b. Uterus has two major parts: i. Corpus (body) ii. Fundus (top of corpus) c. Cervix: neck of the uterus à acts as a mechanical barrier to infectious microorganisms from the vagina d. Uterine wall is composed of three layers i. Perimetrium: outer membrane ii. Myometrium: thick muscular layer iii. Endometrium: uterine lining à functional layer of the endometrium is responsive to the sex hormones estrogen and progesterone. This layer proliferates and sloughs off monthly between puberty and menopause. 3. Fallopian tubes: enter the uterus bilaterally just beneath the fundus; their function is to conduct the ova from the spaces around the ovaries to the uterus. a. Infundibulum: widened end, fringed or fimbriated b. Fimbriae: move, creating a current that draws the ovum into the infundibulum. 3  c. Ampulla: distal third of the fallopian tube, is the usual site of fertilization. 4. Ovaries: female gonads, are the primary female reproductive organs à main functions are secretion of female sex hormones and development and release of female gametes, or ova. a. Ovarian cycle: the process of follicular maturation, ovulation, corpus luteum development, and corpus luteum degeneration—is continuous from puberty to menopause, except during pregnancy or hormonal contraceptive use. Know the role of the different female hormones involved in menstruation, menopause, ovulation, dysmenorrhea, etc. Estrogen is a generic term for three similar hormones: estradiol, estrone, and estriol. Estradiol is the most potent and plentiful of the three and is principally produced (95%) by the ovaries (ovarian follicle and corpus luteum). 1. numerous biologic effects (involve interactions with other hormones)à needed for maturation of reproductive organs, development of secondary sex characteristics, closure of long bones after the pubertal growth spurt, regulation of the menstrual cycle, and endometrial regeneration after menstruation 2. Estrogen also has metabolic effects on the bones, liver, blood vessels, brain and central nervous system, kidneys, and skin. Complementary and Opposing Effects of Estrogen and Progesterone Structure Effect of Estrogen Effect of Progesterone Vaginal mucosa Proliferation of squamous epithelium; Thinning of squamous epithelium; increase in glycogen content of cells; decornification layering (cornification) of cells Cervical mucosa Production of abundant fluid secretions Production of thick, sticky secretions that that favor survival and enhance motility tend to plug cervical os of sperm Fallopian tube Increase of motility and ciliary action Decrease of motility and ciliary action Uterine muscle Increase of blood flow; increase of Relaxation of myometrium; decrease of contractile proteins; increase of uterine sensitization to oxytocin muscle and myometrial excitability to action potential; increase of sensitization to oxytocin Endometrium Stimulation of growth; increase in Activation of glands and blood vessels; number of progesterone receptors accumulation of glycogen and enzymes; decrease in number of estrogen receptors Breasts Growth of ducts; promotion of prolactin Growth of lobules and alveoli; inhibition of effects prolactin effects Follicle-stimulating hormone (FSH) is synthesized and secreted by gonadotrophs of the anterior pituitary gland 1. Regulates the development, growth, pubertal maturation and reproductive processes of the body 2. FSH and luteinizing hormone (LH) act synergistically in reproduction. Luteinizing hormone (LH) is from the anterior pituitary 1. stimulates the corpus luteum to secrete progesterone 4 Gonadotropin-releasing hormone (GnRH) is produced by the hypothalamus; controls the production of LH and FSH. Menstruation à menstrual bleeding (menses); starts with menarche (first menstruation) and ends with menopause (cessation of menstrual flow for 1 year) a. Menarche – related to body weight (especially % of body fat) à trigger a change in the metabolic rate and lead to hormonal changes associated with early menarche b. Cycles = anovulatory at first à may vary in length from 10 to 60 days or more; become more regular as you become an adult (21 to 45 days) c. Common accepted cycle = 28 (27 to 30) days with rhythmic intervals of 21 to 35 days considered normal d. 2 to 8 years before menopause à cycles begin to lengthen (variation related to changing hormones) Menstrual Cycle: HORMONAL FEEDBACK MECHANISM IN THE MENSTRUAL CYCLE Phase of Cycle and Ovarian Hormone Feedback to Resultant Ovarian and Menstrual Levels Hypothalamus and GnRH, FSH, Events Anterior Pituitary and LH Levels Early follicular phase: estrogen levels Negative and All low Ovarian follicle low; minute amount of progesterone inhibitory develops; endometrium secreted proliferates Late follicular (preovulatory) phase: Positive and All surge; LH Process of ovulation estrogen levels high; progesterone stimulatory dominates begins; endometrial increases with small surge before proliferation complete ovulation Ovulatory phase: estrogen levels dip; Negative and All fall sharply Corpus luteum begins to progesterone levels begin to rise inhibitory develop; endometrium enters secretory phase Early luteal phase: estrogen and Negative and All continue to Corpus luteum fully progesterone levels high; progesterone inhibitory decline, but developed; endometrium dominates gradually ready for implantation Late luteal phase: estrogen and Negative and All rise slightly Corpus luteum progesterone levels fall sharply inhibitory; feedback regresses; endometrium lessens slightly breaks down; menstruation begins Menstrual phase: estrogens levels low; Negative and All low More ovarian follicles minute amount of progesterone inhibitory begin to develop; secreted functional layer of endometrium is shed 5 Ovulation Most important event is the rise in LH 1. Decline in the late luteal phase of estrogen, progesterone, and inhibin secretion à FSH to rise à stimulates granulosa cell growth and initiates estrogen production in these cells in the next cycle 2. Slight increase in LH levels 3. Progesterone, proteolytic enzymes, and prostaglandins à trigger mechanisms controlling follicular rupture and release of the ovum The FSH and LH surge also transforms the granulosa cells of the ovulatory follicle into the corpus luteum à secretes estrogen and progesterone in amounts that depend in part on adequate development of the follicle before ovulation Menopause: defined by the point that marks 12 consecutive months of amenorrhea Characterized by: o loss of ovarian follicles à loss of ovarian function o low estradiol and even lower progesterone levels, high FSH and LH levels. o Less androgens are produced, but sensitivity to them is increased because of the lost opposition of estrogen. PRIMARY DYSMENORRHEA SECONDARY DYSMENORRHEA Define: painful menstruation associated with the Patho: pelvic pathologic disorders release of prostaglandins in ovulatory cycles (not 1. Endometriosis (most common) with pelvic disease) 2. Endometritis (infection) Patho: excessive endometrial prostaglandin 3. Adenomyosis production (potent myometrial stimulant and 4. PID vasoconstrictor) 5. Obstructive uterine or vaginal anomalies 1. Elevated levels of prostaglandins à uterine 6. Uterine fibroids hypercontractility, decreased blood flow to 7. Polyps the uterus, and increased nerve 8. Tumors and Ovarian cysts hypersensitivity à PAIN 9. Pelvic congestion syndrome May also have up-regulated cyclo-oxygenase (COX) Non-hormonal intrauterine devices (IUD) enzyme activity à increased synthesis of prostaglandins à leukotriene production is elevated further à increased levels of pain. What does breast milk contain? Breast milk nutrient composition changes over time to meet the changing digestive capabilities and nutritional requirements of the infant. a. Physiologically, breast milk is the most appropriate nourishment for newborns b. Colostrum (produced in low quantities in the first few days postpartum) à rich in immunologic components i. secretory IgA, lactoferrin, leukocytes, and developmental factors (epidermal growth factor) c. Secretory IgA and nonspecific antimicrobial factors, such as lysosomes and lactoferrin, protect the infant against infection, allergies, and asthma 6 Know the male GU anatomy and the function of the glands. External Genitalia Testes are the essential organs of reproduction. Functions include: 1. Production of gametes (sperm) 2. Production of sex hormones (androgens and testosterone). a. They are suspended outside the pelvic cavity because sperm production requires an environment that is 1°C-2°C (1.6°F-3.6°F) cooler than the body. b. The spermatic cord suspends the testes in the scrotal sac c. Tunica vaginalis is the outer covering of the testes d. Tunica albuginea is the inner covering of the testes i. Inward extensions of the tunica albuginea form septa that separate the testis into about 250 compartments, or lobules, each of which contains several tortuously coiled ducts called seminiferous tubules e. The seminiferous tubules constitute the bulk (80%) of testicular volume and are the site of sperm production. Tissue surrounding these ducts contains blood and lymphatic vessel, fibroblastic support cells, macrophages, mast cells, and Leydig cells i. Leydig cells occur in clusters and produce androgens, chiefly testosterone. f. The two ends of each seminiferous tubule join and leave the lobule through a short, straight section called the tubulus rectus g. Sperm travel from the seminiferous tubules into these straight sections, which lead to the central portion of the testis, the rete testis h. From the rete testis, sperm move through the efferent tubules, or vasa efferentia, to the epididymis, where they mature i. The epididymis is a comma-shaped structure that curves over the posterior portion of each testis i. It contains of a highly coiled duct measuring about 5 to 7 cm length, whose structural function is to conduct sperm from the efferent tubules to the vas deferens ii. The tail of the epididymis is continuous with the vas deferens, a duct with muscular layers capable of powerful peristalsis that transports sperm toward the urethra. Sperm are stored in the epididymal tail and vas deferens. Scrotum: encloses and protects the testes, epididymides, and spermatic cord 1. It is a skin-covered fibromuscular sac that is homologous to the female labia majora; skin is thin and has rugae (wrinkles or folds) that enable it to enlarge or relax away from the body 2. Just under the skin lies a layer of connective tissue (fascia) and smooth muscle, the tunica dartos (forms a septum that separates the two testes) à contract and relax to move the testes closer and farther from the body based on environmental temperatures Penis: 1. Functions include: delivery of sperm to the female vagina and elimination of urine 2. Embryonically à homologous to the female clitoris 3. Externally à consists of a shaft with a tip, the glans, which contains the opening of the urethra; (for protection) the skin of the glans folds over the tip of the penis, forming the prepuce, or foreskin 4. Internally à urethra and three compartments: two corpora cavernosa and the corpus spongiosum. The three compartments are separated by Buck fascia and, like the testes, are enclosed by a tunica albuginea. 5. The urethra passes through the corpus spongiosum and ends at a sagittal slit in the glans. If the urethra is not completely surrounded by the corpus spongiosum, the meatus may open on the ventral surface of the penile shaft (hypospadias) or on the dorsal surface (epispadias). 6. Penetration of the female vagina is made possible by the erectile reflex, a process in which erectile tissues within the corpora cavernosa and corpus spongiosum become engorged with blood, generally 20-50 ml. 7 Internal Genitalia 1. The ducts—the two vasa deferentia, the ejaculatory duct, and the urethra—conduct sperm and glandular secretions from the testes to the urethral opening of the penis. 2. The glands—the prostate gland, two seminal vesicles, and two Cowper (or bulbourethral) glands— secrete fluids that serve as a vehicle for sperm transport and create an alkaline, nutritious medium that promotes sperm motility and survival. Together, the sperm and the glandular fluids comprise semen 1. As sperm leave the ampulla of the vas deferens à the seminal vesicles (pair of glands – each 4-6cm long, lie behind the urinary bladder in front of the rectum) secrete a nutritive glucose-rich fluid into the ejaculate (semen) a. Seminal vesicles provide fructose as a source of energy for ejaculated sperm and secrete prostaglandins that promote smooth muscle contraction assisting with sperm transport 2. The ducts of the seminal vesicles join the ampulla of the vas deferens to become the ejaculatory duct, which contracts rhythmically during emission and ejaculation. Prostate gland: 1. Size of a walnut, has three zones, and surrounds the urethra 2. Composed of glandular alveoli and ducts embedded in fibromuscular tissue 3. Prostate growth, development, and function are regulated by androgens and the androgen receptor (without them) à prostate is at risk for hyperplastic and malignant growth 4. Nerves required for penile erection travel along the posterolateral surface of the prostate. 5. Included in prostate epithelial secretions: a. Prostate-specific antigen (psa), cytokeratins, prostate-specific membrane antigen (psma), and prostate-specific acid phosphatase (prostate secretions contribute to the ejaculate) 6. While semen moves through the prostatic portion of the urethra à the prostate gland contracts rhythmically and secretes prostatic fluid into the mixture 7. Prostate fluid is a thin, milky substance with an alkaline PH that helps sperm survive in the acid environment and the female reproductive tract 8. Clotting enzymes and fibrinolysin in prostatic fluids help mobilize sperm after ejaculation Cowper glands: 1. Bulbourethral glands – whose ducts secrete mucus into the urethra near the base of the penisà last pair of glands to add fluid to the ejaculate. 2. Ejaculation occurs as semen reaches the base of the penis and muscles there begin the rhythmic contractions that push semen out. 3. In normal ejaculation between 2 and 6 ml of semen containing 75 million to 400 million sperm 4. About 98% of the ejaculate consists of glandular fluids; 60% to 70% of volume comes from the seminal vesicles and 20% from the prostate 5. Ejaculate of a man who has undergone vasectomy (a surgical procedure that prevents sperm from entering the bas deferens) is not reduced by much: about 2%. 6. During vasectomy, the vas deferens are severed and then tied in order to prevent sperm from entering the ejaculate; this procedure is used for permanent male birth control. 8 What is the pathophysiology behind the signs and symptoms of menopause? Define: cessation of ovulation and menses caused by ovarian failure; normal, developmental event marking the end of reproduction Menopause is universally experienced by midlife women at the average age of 50.5-51.4 years in North America with variability between 40-60 years. Premature menopause (cessation of ovulation before 40 years of age) Causative factors: genetics (50% variation in age) socioeconomic status race, parity oral contraceptive use lifestyle (smoking or weight) can occur 2 years sooner on average for smokers; thinner women also tend to experience menopause at a slightly younger age Patho: term “climacteric” à gradual changes of ovarian function that start before menopause à symptoms with loss of ovarian function due to loss of ovarian follicles resulting in reduced ovarian production of estradiol, increased FSH and LH, and decreased inhibin (inhibits release of FSH). It is defined by the point that marks 12 consecutive months of amenorrhea PRIMARY CHANGES OF MENOPAUSE Perimenopause: transitional period between reproductive and nonreproductive years, lasting 2 to 8 years. Five to 10 years before menopause, approximately 90% of women note mild to extreme variability in frequency and quality of menstrual flow. Hormone changes include: o erratically higher estradiol levels o decreased progesterone levels (in normal ovulatory, short luteal phase, or anovulatory cycles) o disturbed ovarian-pituitary-hypothalamic feedback relationship with higher LH levels This stage varies among women and from cycle to cycle in the same woman. Estradiol levels remain in the normal to slightly elevated range until about 1 year before menopause. OVARIAN Utero à the number of follicles steadily decreases though activation, maturation, and atresia Starting in the late 30s (10 to15 years before menstruation ceases) à process accelerates until the supply of follicles is depleted à increased FSH stimulation, delayed and attenuated LH surges, and a decrease in inhibin Increased FSH stimulation seems to accelerate follicular loss, declining inhibin production, slightly elevated estradiol levels and decreasing anti-müllerian hormone Attenuated LH surges à impaired hypothalamic responses to estradiol positive feedback UTERINE Location affected à primarily in the endometrium Increase in anovulatory cycles allows for proliferative growth of the endometrium The longer exposure to estrogen à greater thickness of the endometrium à heavy/unpredictable uterine bleeding (50% of perimenopausal women) BREAST Glandular tissue becomes involuted Fat deposits and connective tissue increase TISSUE Breasts become smaller and lose firmness. 9 UROGENITAL Ovaries shrink TRACT Uterus atrophies Vagina shortens, narrows and loses some elasticity Lubrication of the vagina diminishes, and vaginal pH increases à higher incidence of vaginitis The cervix atrophies, and the cervical os shrinks Vaginal epithelium atrophies Labia majora and minora become less prominent Some pubic hair is lost Urethral tone declines (along with muscle tone throughout the pelvic area) à urinary frequency or urgency, or UTIs and incontinence à estrogen deficiency **Regular sexual activity/orgasm may diminish some of these changes; sexually active women have less vaginal atrophy. SYSTEMATIC Vasomotor flushes (“hot flashes”) à rise in skin temperature, dilation of peripheral blood vessels, increased blood flow in the hands, increased skin conductance, and a transient increase in HR followed by a temperature drop and profuse perspiration Usually occurs in the face and neck and may radiate to chest and other body parts Night sweats, dizziness, nausea, HA, or palpitations may accompany the flush Cause of vasomotor flushing: rapid changes in estrogen may result in loss of negative feedback over hypothalamic noradrenaline synthesis (primary neurotransmitter involved in thermoregulation) Estrogen modulates adrenergic receptors à decrease in estrogen in menopause à decrease the number of receptors à increased noradrenaline levels and hot flushes CARDIAC Risk of CHD increases significantly after menopause Estrogen is known to foster favorable lipid profiles and to have beneficial effects on vessel endothelium through production of nitric oxide Once postmenopausal (decrease estrogen levels) à BP and LDL levels rise, central adiposity and weight increases, and HDL levels lower SKELETAL Bone mass is reduced (due to low estrogen levels) à increased brittleness and porosity à increased risk of osteoporosis and fracture OTHER Emotional stress with unpredictable mood swings, weight gain, migraine headaches, and insomnia Lower estrogen levels à decrease skin thickness and diminish skin elasticity à increasing skin dryness and wrinkling. 10