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Chapter 16 Notes
The Reproductive System
A. Function – to produce offspring B. Primary sex organs – gonads produce gametes (exocrine) and secrete sex hormones (endocrine) a. produce eggs b. secrete progesterone and estrogens C. Accessory Organs – all others (ducts, glands, and external genitalia) D. Sex hormones 1. Development and function of reproductive organs, behaviors, and drives 2. Influence growth and development of other organs and tissues throughout body 1. contains testes 2. provides temp cooler than core 3. responds to changes in temp – dartos and cremaster muscles 1. Size of a large olive, 4 cm x 2.5 cm 2. 2 tunics a. Tunica Vaginalis (outer) – derived from peritoneum, continuous with abdominal cavity (inguinal canal) b. Tunica Albuginea (inner) (1) Divides testes into lobules (2) Each lobules contains 1 to 4 seminiferous tubules and Leydig cells (3) Seminiferous tubules in testes converge into tubulus rectus, which convey sperm to the rete testis a. testicular arteries b. testicular veins – pampiniform plexus – cools arterial blood 4. Ennervation – autonomic, special sensory nerves 5. Testicular cancer, although rare, is the most common cancer in men ages 15-35, treated by orchiectomy + a. hugs external surface of testis b. site of sperm maturation and storage c. sperm are conveyed from rete testis of testes into efferent ductules d. Sperm are transformed here from large non-motile cells to small flagellated cells a. from epididymis to seminal vesicle b. passes over pubic bone, up over and behind bladder c. sperm are propelled by peristalsis during ejaculation d. fuses with duct of seminal vesicle to form the short ejaculatory duct e. vasectomy – small incision in scrotum, vas cut and clamped to interrupt flow of sperm for birth control a. from bladder to tip of penis b. part of both urinary and reproductive systems c. three regions (1) Prostatic urethra (2) Membranous urethra (3) Spongy or penile urethra D. Accessory Glands – produce most of semen a. Paired, finger size glands posterior to bladder b. produce ~ 60% of semen volume c. yellowish viscous alkaline fluid containing (1) fructose (2) ascorbic acid (3) coagulating enzyme vesiculase (4) prostoglandins d. mixes with sperm in ejaculatory duct before entering urethra a. encircles urethra just inferior to bladder b. secretes ~ 33% of semen volume c. milky, slightly acid fluid containing enzymes (acid phosphatase & fibrinolysin) d. activates sperm e. hypertrophy blocks flow of urine – treated surgically or with balloon catheter f. Cancer of prostate 3rd most common cancer in men (1) detected via digital exam (2) detected by blood test (PSA and acid phosphatase) (3) if detected early can be treated with surgical removal (4) if detected after metastasis, treated by castration and/or androgen blocking drugs a. pea-sized glands inferior to prostate b. secrete thick, clear mucus that drains into spongy urethra c. believed to neutralize any traces of urine remaining in urethra and possibly act as lubricant 1. Along with scrotum make up male external genitalia 2. Delivers sperm into female reproductive tract 3. Perineum – diamond-shaped region between pubic symphysis anteriorly, coccyx posteriorly, and ischial a. Root b. Shaft or body with enlarge tip (glans penis) 5. Covered by loose skin which forms distal cuff around glans penis called prepuce or foreskin, may be removed a. spongy urethra b. Three corpora – long cylindrical bodies of spongy connective tissue and smooth muscle with many vascular spaces that fill with blood during sexual excitement to cause an erection (1) Corpus spongiosum – surrounds urethra, expands distally to form glans and proximally to form part (2) Corpus cavernosa – one on each side, form bulk of penis 1. Milky, white, sticky mixture of sperm and accessory gland secretions 2. Provides transport medium and nutrients and chemicals that protect and activate sperm and facilitate their movement. Mature sperm have little cytoplasm or stored nutrients 3. Fructose from seminal vesicles provides fuel 4. Prostaglandins decrease viscosity of mucus guarding entrance to uterus and causes reverse peristalsis of Fallopian tubes to help move sperm to egg 5. Hormone relaxin and certain enzymes enhance sperm motility 6. Alkaline pH (7.2-7.6) neutralizes acid environment of vagina (pH 3.5-4) 7. Antibiotic chemical destroys bacteria 8. Clotting factors coagulate semen after ejaculation 9. Fibrinolysin liquifies it so sperm can swim 10. Only 2-5 ml per ejaculate, but contains 50-100 million sperm per ml III. Physiology of Male Reproductive System a. enlargement and stiffening of penis b. due to engorgement of erectile bodies with blood c. controlled by parasympathetic reflexes a. expulsion of semen from duct system due to smooth muscle contractions b. promoted by sympathetic nervous system c. accompanied by pleasurable sensations, generalized muscle contractions increased blood pressure and B. Spermatogenesis - sperm production (see figure 28.7, pg 924) a. Begins in puberty, continues throughout life a. Primitive stem cells called spermatogonia that line the seminiferous tubules undergo rapid mitotic division to produce zillions more like them b. At puberty, FSH from anterior pituitary stimulates the divisions to change; from then on, divisions of spermatogonia produce one spermatogonium and one Type B daughter cell, which will go on to form sperm c. Primary spermatocyte - Type B daughter cell that has started meiosis (two successive cell divisions that result in four daughter cells, each of which carries one half the normal number of chromosomes) d. Secondary spermatocytes - the two cells that resulted from the first division of the Type B daughter cell e. Spermatids - the four cells that result from the second division of the two secondary spermatocyctes f. Spermiogenesis - conversion of spermatids into sperm (2). what still remains is compacted into (a). Head - nucleus over which is acrosome (contains enzymes that help sperm penetrate egg) (b). Midpiece - contains centriole and many mitochondria (c). Tail - contains protein filaments that arise from centriole in midpiece 3. After spermatogenesis, the immature sperm are released into the lumen of the seminiferous tubules and moved by peristalsis into epididymis for further maturation 1. Produced by interstitial cells of testes, activated by LH (luteinizing hormone) from anterior pituitary during a. Reproductive organs grow to adult size (1). deepening of voice due to enlargement of larynx (adam’s apple) (2). increases hair growth, particularly in axillary and pubic areas and on face The Female Reproductive System
C. Nurtures and protects developing fetus c. Broad ligament - fold of peritoneum that encases pelvic organs 3. Internal structure - contains ovarian follicles, which consist of 4. Ovulation - ejection of egg from ovary, usually occurs every 28 days a. to guide egg from ovary to uterus b. site of fertilization a. Fimbriae - fingerlike projections of distal end, extend over ovaries & create currents to guide egg inside b. Tube - ciliated, peristaltic, to push egg toward uterus (takes 3 to 4 days) a. receives, retains, and nourishes fertilized egg b. passageway for sperm to fallopian tubes 2. Located between bladder and rectum, size and shape of pear in female who hasn’t been pregnant b. Fundus - portion above fallopian tubes c. Cervix - narrow outlet (hole in cervix is os) a. Endometrium - innermost layer, sloughs off periodically, about every 28 days b. Myometrium - smooth muscle, middle layer c. Epimetrium - outermost layer, also the visceral peritoneum 1. Thin walled, muscular, 3 to 4 inches long, collapsed tube from cervix to exterior of body b. Receives the penis during sexual intercourse 3. Hymen - thin fold of mucosa covering vaginal opening E. Vulva (External genitalia) see fig 28.14 pg 934 1. Mons pubis - Hair covered, fatty, rounded area overlying pubic symphysis 2. Labia Majora - elongated hair covered skin folds running posteriorly from mons pubis 3. Labia Minora - delicate, hair free folds enclosed by labia minora 4. Vestibule - area enclosed by labia minora a. Clitoris - corresponds to male penis, composed of sensitive eretile tissue that becomes swollen with blood during sexual excitement, but lacks reproductive duct c. Greater Vestibular Glands - one on each side, secrete lubricants for distal vagina during intercourse 5. Perineum - diamond shaped region between the anterior end of the labial folds, the anus and the ischial III. Female Reproductive Functions and Cycles 1. in ovary of female fetus, stem cells (oogonia) multiply by mitosis to form primary oocytes 2. primary oocytes push into ovary and are surrounded by a single layer of cells to form primary follicles 3. by birth, all oogonia have undergone mitosis to become oocytes, and no oogonia remain 4. primary oocytes start into meiosis (prophase I) where they stay until stimulated by FSH 5. at puberty, FSH from ant pituitary stimulates a small # of primary follicles to develop each month 6. Follicle develops fluid filled chamber called antrum, and begins to undergo remainder of meiosis I 7. Cell division in meiosis I is uneven, producing one secondary oocyte(large) and polar body, which dies 8. Surge of LH from ant pituitary causes follicle to rupture out of ovary (ovulation), may cause pain 9. Part of follicle remains in ovary and is stimulated by LH to become corpus luteum 10. Corpus luteum produces progesterone and gradually deteriorates 11. Part of follicle stays with secondary oocyte and is called corona radiata B. Ovarian cycle - steps 5 through 10 above C. Menstrual Cycle - cyclic changes of the endometrium undergoes month to month in response to ovarian b. ovulation happens midway through cycle (14 days from beginning of menstrual period) c. ovarian hormones controlled by ant pituitary via FSH and LH a. Days 1-5: Menses - endometrial lining is sloughed off, passes through vagina to outside of body. b. Days 6-14: Proliferative Stage - growing follicle in ovary produces increasing amounts of estrogen, which causes repair of endometrium, formation of mucus and other glands in endometrium, and increase in blood supply to endometrium. At the end of this stage, ovulation occurs due to a sudden surge in LH from the ant pituitary c. Days 15-28: Secretory phase - rising progesterone levels from corpus luteum(due to surge in LH described above) cause even more endometrial development. If fertilization does not occur, corpus luteum deteriorates, which causes fall in levels of both estrogen and progesterone, causing the lining to slough (and we’re back to day one!). If fertilization does occur, the embryo produces Human Chorionic Gonadotropin (HCG), which is like LH and maintains the corpus luteum, which still produces progesterone, so the endometrial lining is not sloughed. 1. Estrogen is actually three different molecules, all produced by the follicles at puberty in response to FSH 2. Estrogen causes the appearance to female secondary sex characteristics a. Enlargement of organs of female reproductive system (uterus, tubes, vagina, external genitals) c. Appearance of axillary and pubic hair d. Fat deposition under skin in general, particularly over hips and breasts a. From corpus luteum, produced in response to LH from ant pituitary b. Works with estrogen to establish menses c. Maintains pregnancy and prepares breasts for milk production (but is then from placenta) 1. Present in both sexes, functional only in females in response to estrogen(development) and progesterone 2. Function - to produce milk to nourish a newborn a. Modified sweat glands b. Anterior to pectoral muscles of thorax c. Pigmented area is areola d. Nipple - central protrusion, contains openings to lactiferous ducts e. Each contains 15 - 25 lobes that are padded and separated from each other by connective tissue & fat. f. Each lobe contains lobules, which contain clusters of alveolar glands that produce milk during lactation g. Alveolar glands send milk into lactiferous ducts that open into nipple PREGNANCY AND FETAL DEVELOPMENT
I. Fertilization - union of male and female gametes 1. Oocyte is viable for 12 to 24 hours after ovulation 2. Sperm is viable for 12 to 48 hours (or up to 72 hrs with “supersperm”) after ejaculation 3. Sexual intercourse must occur no more than 72 hrs before ovulation and no more than 24 hrs after ovulation B. Occurs in fallopian tube, no more than 1/3 of the way down toward uterus 1. Acrosomes of hundreds of sperm rupture and “eat” a pathway through follicle cells to membrane of oocyte 2. The head only of the first sperm to make contact with the oocyte membrane is pulled into the cytoplasm. The cell membrane instantaneously undergoes depolarization which prevents polyspermy (more than one sperm entering oocyte). If polyspermy does occur, the resulting embryo contains too much genetic material and is nonviable. 3. Secondary oocyte nucleus completes meiosis 4. Ovum and sperm nuclei rupture, releasing chromosomes 5. New nuclear membrane forms around combined chromosomes 6. Fertilized egg is now known as a zygote or conceptus D. Gestation period = 280 days from first day of last menstrual period to birth A. Events from fertilization through implantation (~ 2 wks) 1. rapid mitotic divisions of the conceptus 2. no time for growth between divisions, so cells become progressively smaller C. Cells form a ball shape, then fold in on themselves - blastula D. Blastula arrives in uterus in two to four days, then floats freely for 2 or 3 days, receiving nourishment from E. Implantation (6 - 14 days after ovulation) - 1. blastocyst burrows into endometrial lining, usually high in uterus. 2. Blastocyst secretes human chorionic gonadotropin (HCG) which acts like LH to maintain corpus luteum, so it continues to secrete progesterone and uterine lining is not sloughed. HCG is the hormone tested for in pregnancy tests, and is usually detectable in the mother’s blood by one week after fertilization 3. Ectopic pregnancy - embryo implants somewhere besides uterus, usually uterine tube F. Placentation - formation of placenta, usually complete by third month 1. consists of chorionic villi that interdigitate with endometrium 2. Starts producing progesterone so by third month corpus luteum is no longer needed and deteriorates 3. Toward end of pregnancy also produces other hormones a. Relaxin, which causes relaxation of ligaments to widen the pelvis (and feet!) b. Human placental lactogen - works with estrogen and progesterone to prepare breasts for lactation G. Outer cell layers become embryonic membranes 1. amnion - “bag of waters”, closest to baby, contains amniotic fluid that cushions, protects, maintains constant temp of baby, prevents adherence of fetal parts to one another A. 3rd through 8th week of development, period of great cell differentiation 1. endoderm - innermost, becomes lining of digestive tract plus liver, pancreas, thyroid, lining of urogenital 2. mesoderm - middle layer, becomes muscles, bones, blood, etc 3. ectoderm - outermost layer, becomes skin and nervous system A. 9th week through birth, period of both differentiation and growth 2. Vein carries cleaned, oxygenated, nutrient-rich blood from placenta to liver. Part of blood feeds liver, but most bypasses liver through ductus venosus to inferior vena cava, to right atrium. 3. In right atrium, some blood passes directly into left atrium though foramen ovale 4. In right atrium, some blood passes into right ventricle then out pulmonary trunk and then is shunted into 5. Blood from lower aortic branches goes into umbilical arteries back to placenta A. Uterus enlarges tremendously, from pelvic cavity to xiphoid process 1. Changes center of gravity, causing lordosis and back pain (also due to relaxin loosening SI joints) 2. Presses on bladder causing frequency, urgency, & stress incontinence (kidney also makes more urine) 3. Presses on inferior vena cava, causing back pressure on veins of legs and feet 4. Presses on stomach, causing reflux, heartburn 5. Presses on colon, causing constipation B. Blood volume increases by up to 40 percent, increases blood pressure & heart rate C. Elevated levels of estrogens and progesterone cause 1. nasal mucosa to swell, causing stuffiness and nosebleeds D. Weight gain - no “ideal” because each mother is different 1. Mother is NOT “eating for two”, but requires an average of 300 more calories 2. Sum of weight increase from fetus, placenta, increased blood volume, uterus, breasts ~ 29 lbs A. Usually occurs within 2 weeks of due date (280 days from last menstrual period) B. Labor - the events that result in parturition a. In response to fetal hormones, placenta produces high levels of estrogen 1. stimulates the myometrial cells to form oxytocin receptors 2. Antagonizes progesterone’s quieting influence on myometrium b. Myometrium becomes increasingly ‘irritable’, woman may have false labor(Braxton Hicks contractions) c. Fetus produces oxytocin, which causes placenta to produce prostaglandins, both of which are powerful uterine muscle stimulants. (aspirin and ibuprofin are antiprostaglandins and can inhibit labor) d. Stress on mother causes her to also release oxytocin from hypothalamus, kicking in positive feedback e. Braxton-Hicks contractions - weak, irregular uterine contractions as uterus begins to respond to high levels of estrogen near end of pregnancy a. Dilation state - from onset of labor until cervix is fully dilated (10 cm diameter) (1). Contractions start in upper uterus and travel down to pelvis (2). As infants head pushes on cervix, it thins and dilates (3). Amnion ruptures, releasing amniotic fluid b. Expulsion state - from full dilation to birth of infant (1). contractions by now are occurring every 2-3 min and are 1 min long (4). Crowning - when baby’s head is distending the vulva, at which point an episiotomy is made to (5). Presentation - part of baby to exit first (6). Dystocia - prolonged, difficult labor, sometimes ended by a Cesarean section, delivery of the infant through a surgical incision made through the abdominal and uterine walls c. Placental stage - delivery of the placenta (2). uterus is still contacting, which compresses uterine blood vessels, limits bleeding and causes (3). Placenta and membranes = afterbirth A. Production of milk by the hormone-prepared mammary glands B. Rising levels of estrogens, progesterone, and lactogen stimulate hypothalamus to secrete prolactin-releasing hormone, which stimulates anterior pituitary to secrete prolactin. 2. less lactose than milk, almost no fat, but more protein, vit A, and minerals 3. milk and colostrums both have high levels of IgA D. Prolactin release gradually decreases and mechanical stimulation of nipples continues milk production 1. released from posterior pituitary in positive feedback loop during nursing 2. causes let-down reflex - actual ejection of milk 3. also stimulates uterine contractions 1. Contents are better absorbed than cow's milk 2. Contains not only IgA, but complement, lysozyme, interferon, and lactoperoxidase, interleukins, prostaglandins, antibacterial glycoproteins, natural laxatives VII. The Newborn (neonatal period = 1st 4 weeks) 1. Test used to evaluate status of newborn 2. Done at 1, 5 and 10 minutes after birth 3. Infant is rated from 0-2 in 5 different areas; ratings are added for total score 0-10 4. <5 at 1 min usually requires major resuscitation 5. Does not predict neurological outcome 1. Hypothalamus hasn't "kicked in" yet 1. Prematurity = < 5.5 lbs - respiratory effort greater due to less surfactant 2. Congenital - any abnormal condition someone is born with, whether inherited or otherwise 3. Hereditary - condition coded for in a person’s genes 4. Meconium - tarry green-black paste containing sloughed-off epithelial cells, bile - babies first feces 5. Physiologic jaundice - jaundice that occurs 3-4 days after birth when immature liver cannot keep up with


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