Notes on Reproductive System
Notes on Reproductive System Biol 2230-001
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This 11 page Class Notes was uploaded by Madeline Notetaker on Wednesday January 27, 2016. The Class Notes belongs to Biol 2230-001 at Clemson University taught by Dr. John Cummings in Spring 2016. Since its upload, it has received 32 views. For similar materials see Human Anatomy & Physiology II in Biological Sciences at Clemson University.
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Date Created: 01/27/16
Reproductive System Male Anatomy Testes- reproductive organ Scrotum Epididymis Ductus deferens Ejaculatory duct Urethra Penis Seminal vesicles Prostate gland Bulbourethral glands Testes Tublues Lobules- little compartments Seminiferous tubules- site of sperm production Within lobules Tubulus rectus Straight tubule Rete testis Efferent ductules Epididymis Store sperm Histological Composition Seminiferous tubules Produce sperm Interstitial cells Between Seminiferous tubules “Leydig” cells Produce testosterone Testicular Blood Flow Supplied by testicular arteries Pass through pampiniform plexus Where supply blood transfer heat to returning blood Drained by testicular veins Scrotum Sac-like structure composed of skin and superficial fascia Testes separated into compartments Allows maintenance of optimal temperature 2 muscles that control how close testis are to body dartos and cremaster muscles Penis Specialized copulatory organ Mechanism to get sperm from male to female Glans covered with prepuce (foreskin) Circumcised is removal of it Erectile Tissue Corpus spongiosum (1X) Surrounds urethra Fills with blood also so urethra stays open to deliver sperm Corpora cavernosa (2X) Engorges with blood when aroused Fills cavernous tissue Stays entrapped, veins returning blood are squeezed Both spongy network of connective tissue, smooth muscle and vascular space Accessory Ducts Epididymis Sperm stored and matured here (20 days) Can be stored here for several months then phagocytes Even sperm that leave here are not capable of fertilizing egg yet Ductus (vas) deferens From each testies Ejaculatory duct (2) Then connect to urethra Urethra Transcends penis Accessory Glands Seminal vesicles (2) Secretes alkaline fluid (basic pH) bc female system has acidic pH so surrounds sperm and protects it from acidic environment Prostate gland (1) Release nutrient sources and enzymes to give sperm energy and activate Bulbourethral glands Secrete mucus that cleanse urethra/clean pathway Stimulated to act before other glands Viscous so also aids in lubrication for insertion Male Reproductive Physiology Erection Sexual arousal causes parasympathetic reflex to release nitric oxide at/ near penis NO causes arteriole dilation more blood Erectile bodies fill with blood becomes erect Corpora cavernosa expands, compressing drainage veins blood is trapped Bulbourethral glands also stimulated release their fluid Ejaculation Continued stimulation provokes massive sympathetic nerve discharge Reproductive ducts and accessory glands contract, pushing contents into urethra Bladder sphincter muscle constricts Muscles of penis undergo rapid series of contractions Semen propelled from penis Spermatogenesis= sperm production Diploid spermatogonia undergo mitosis to produce type A and B daughter cells (still diploid) Type A replaces itself Type B cells are primary spermatocytes (diploid) Primary spermatocytes undergo meiosis I to become secondary spermatocytes (now haploid) Secondary spermatocytes undergo meiosis II to become spermatids (still haploid) Spermiogenesis Spermatid decreases most cytoplasmic volume and forms a tail Finished product known as spermatozoon Midpeice has lots of mitochondria DNA in head (haploid) Cap called acrosome is vesicle that contain enzymes that digest coverings on egg Flagellum is just propeller Sustentacular Cells (sustain sperm) Aka nurse cells, sertoli cells Protect developing spermatocyes from male immune system Blood-testis barrier= connection between circulatory system and testis Nourish dividing cells Help move cells to lumen Secrete testicular fluid Functions as transport medium in lumen to get to epididymis Dispose of eliminated cytoplasm Phagocytizing them Regulate spermatogenesis Takes 72 days to make sperm Hormonal Regulation Hypothalamus releases GnRH GnRH stimulates release of pituitary gonadotropins FSH and LH Have effect on male reproductive tract Role of FSH FSH stimulates Sertoli cells to release androgen-binding protein (ABP) ABP causes spermatogonia to accumulate testosterone Binds to testosterone Stimulates division process Role of LH LH causes interstitial cells to secrete testosterone Also causes small amount of estrogen Role of Testosterone Stimulates spermatogenesis= production of sperm Inhibits GnRH (when gets high) Inhibits gonadotropin release (FSH and LH) Has anabolic effects on accessory reproductive organs Causes male organs to develop Promotes male secondary sex characteristics Hair, deeper voice, oily skin, inc bone density and muscle mass Boosts BMR (basal metabolic rate) Influence behavior Inc sex drive, aggression Role of Inhibin Hormone produced by Sertoli cells when sperm count is high Inhibits release of FSH and GnRH Slows sperm production Female Anatomy Ovaries Site of gamete production Oviducts Uterus Vagina External genitalia Mammary glands Ovaries Site of gamete production in females Gametes formed in cortex (outer layer) before birth Immature Gametes exist as ovarian follicles Oocyte (gamete) plus follicular (if 1 layer) or granulosar (if more than 1 layer) cells around it Ovarian Follicles Primordial follicle 2 million Most are resorbed by body At puberty, cycling begins and some are stimulated to start maturing 4 or 5 start and become primary follicle Primary follicle Surrounded by granulosar cells 4 or 5 start Generally only 1 finishes Become secondary follicle Secondary follicle Has fluid filled component Continues to develop and get larger Graafian follicle Lot of liquid Oocyte is suspended on stalk Eventually ruptures Ovulation Egg released into peritoneal cavity not directly into duct Only one ovulating generally because only one reaches Graafian phase Corpus luteum Glandular product that secretes hormones Takes over progesterone production Degenerates if not pregnant Oviducts Aka fallopian tubes Ovulated oocyte released into peritoneal cavity Ciliated fimbriae sweep oocyte into oviduct Through infundibulum, past ampulla, into isthmus Ultimately transported to uterus *Ampulla is the normal site of fertilization *if implanted anywhere but uterus, called ectopic pregnancy Uterus Thick-walled muscular (smooth muscle) organ that receives, retains and nourishes fertilized ovum Gestation Consists of: Body Fundus- above where oviducts enter Cervix- where connects to vagina Internal os- opening at top of canal through cervix External os- bottom of canal Uterine Wall Layers Perimetrium Myometrium Endometrium Endometrium Strata (2) Stratum functionalis Lost with menstruation The layer ready for implantation Stratum basalis- produces Stratum functionalis Stimulated by hormones Vagina Female organ of copulation Where sperm is deposited Birth canal Also for blood flow during menstruation Acidic environment To prevent pathogen entry that could destroy developing embryo Hymen Thin membrane of tissue that covers external vaginal orifice Fragile (may or not be present) External Genitalia (Vulva) Mon pubis Pad of fat on top if pubic symphysis Labia majora Set of lips with hair follicles associated Labia minora Lips deep to majora Greater vestibular glands Upon sexual arousal secrete mucus that acts as lubricant Clitoris Like penis, composed of spongy tissue that engorges with blood during sexual arousal Perineum Tissue between vulva and anus Tends to tear during childbirth Mammary Glands (modified sweat gland) Males also have them but don’t develop Produce milk to nourish newborn Divided into Lobes Lobes divided into Lobules Alveoli Sacs that produce secretion Site of milk production Lactiferous ducts Lactiferous sinus Point where all ducts come together Nipple Point of suckling Aroela Ring of pigmented tissue Oogenesis= production of female gamete (Pre-puberty) Diploid oogonia undergo mitosis to produce primary oocytes (still diploid) Incorporate follicular cells (one layer of cells surrounding) to become primordial follicles (oocyte with follicular cells) Born with 2 million primordial follicles, but only 400,000 at puberty, and only ovulate about 500 Primary oocytes start, but do not complete, meiosis I Arrested at prophase I Oogenesis (Post-puberty) Meiosis I completes and produces the first polar body and a secondary oocyte Only occurs in about 4-5 oocytes Polar body involved in providing nourishment to egg First polar body undergoes meiosis II and produces two polar bodies Secondary oocyte begins meiosis II but arrests at metaphase II Wont finish unless fertilization occurs Secondary oocyte is ovulated Oogenesis (Post-ovulation) If fertilization: Secondary oocyte completes meiosis II Produces ovum and polar body If no fertilization: Secondary oocyte degenerates and expelled with lining of uterus Ovarian Cycle (3 phases) Follicular phase Associated with development of follicle in ovary Ovulation Moment of ovulation when secondary oocyte is released from ovary Luteal phase Associated with activity of corpus luteum Last 14 days of cycle *On average ovarian cycle is 28 days (between 21-40) Varies in how long follicular phase is Follicular Phase Primordial follicle (at birth) becomes primary follicle under hormonal influence Primary follicle becomes secondary follicle Has a fluid filled portion Theca folliculi forms Connective tissue that also secretes estrogen Theca and granulosa cells produce estrogens Zona pellucida forms Transparent membrane rich in glycoproteins that are receptors for sperm Antrum forms Secondary follicle becomes Graafian follicle Corona radiata forms “stalk” that oocyte sits on Ovulation Ovary wall ruptures and expels secondary oocyte and corona radiata into peritoneal cavity Where fimbriae move into oviduct Number ovulated increases with age *Can predict time of ovulation by temperature, viscosity of cervical mucus, and pain Twins: Identical= one oocyte ovulated, fertilized ovum divides Fraternal= ovulates more than one, each fertilized by different sperm, each has own placenta Luteal Phase Corpus hemorrhagicum forms Short lived structure right after ovulation Has blood in it Quickly resorbed Corpus hemorrhagicum resorbs, but granulosa and theca cells produce corpus luteum Corpus luteum secretes progesterone and estrogen Continues until placenta forms and takes over if fertilization occurs Progesterone keeps uterus ready to receive embryo Continues until placenta forms if fertilization Becomes corpus albicans if no fertilization Scar tissue Hormonal Regulation of ovarian cycle Sensitivity of hypothalamus to estrogen changes at puberty Less sensitive Hypothalamus secretes GnRH In rhythmic pulses GnRH promotes FSH and LH production Takes 3 years to become regular “menarche” Role of FSH FSH stimulates follicle cells, causing growth and maturation of follicle Role of LH (Early in Cycle) LH causes thecal cells to produce androgens (DHEA) Androgens converted to estrogen by granulosa cells Role of Estrogen Initial rise in estrogen level inhibits release of FSH and LH Still produced but builds up Stimulates follicle development Therefore increases estrogen production Increasing estrogen level causes burst of LH Non-cyclic Role of Estrogen Anabolic effects on female reproductive tract Support short-term growth spurt of girls at puberty Promotes female secondary sex characteristics Role of LH (Mid-cycle) LH surge stimulates completion of meiosis I by dominant primary follicle Stimulates ovulation This inhibits estrogen production Transforms ruptured follicle into corpus luteum Thus stimulates progesterone and estrogen production Role of Progesterone Inhibits FSH and LH production Progesterone secretion only lasts about 10 days Hormone levels at absolute lowest at end of ovarian cycle Role of Inhibin Inhibin is produced by corpus luteum Inhibit FSH and LH production Uterine Cycle (menstrual cycle) Menstrual phase Bleeding Day 1-5 Proliferative phase Secretory phase Menstrual Phase Ovarian hormones at lowest level Functional layer of endometrium detaches Menstruation occurs By day 5, follicles are producing estrogen Proliferative Phase Estrogen levels increase Endometrium rebuilds itself Progesterone receptors develop in endometrial cells Continues until ovulation Secretory Phase Progesterone causes endometrium to prepare for implantation and forms cervical plug Continues as long as there is progesterone Decreasing progesterone and LH levels initiate breakdown of endometrium Then cycle starts all over again Female Sexual Response Arousal similar to male Parasympathetic nervous cavity- excitement Blood engorgement in erectile tissue Vestibular gland activity Secrete mucus to prepare for insertion Continued stimulation may result in orgasm Not required for conception Orgasm does not include ejaculation or refractory period (where cant be stimulated again) Human Sexual Development Gender determined by genetic composition of sperm Male determines sex of baby SRY gene XX= girl XY= boy Embryo sexually indifferent until approx. 2 months post-conception Both genders look exact same Sexual Differentiation Gonadal ridges begin formation about 5 weeks post-conception 2 sets of ducts develop Müllerian (female) and Wolffian (male) ducts Only one set maintained; which one depends on sex Primordial germ cells are deposited Will become spermatogonia or oogonia Genital tubercle develops (will become external genitalia) Contains: Urethral groove Urethral folds Labioscrotal swellings Sexual Differentiation (Male) Seminiferous tubules form in gonadal ridges and link with Wolffian ducts Developing testes secrete AMH (anti Müllerian hormone) which causes Müllerian duct to degenerate Genital tubercle enlarges to form penis Urethral folds fuse to form urethra Labioscrotal folds fuse to form scrotum Testosterone production guides secondary sexual development Testes descend into scrotum approx 2 months before birth Sexual Differentiation (Female) Gonadal ridges form ovaries Follicles form in cortex of ovaries Müllerian ducts differentiate Wolffian ducts degenerate No hormone needed Genital tubercle gives rise to clitoris Urethral groove becomes vestibule Urethral folds stay unfused and become labia minora Labioscrotal folds stay unfused and become labia majora Ovaries also descend, but only to pelvic brim
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