Uniqueness of Reproductive System - Physiology and Anatomy - Lecture Slides, Slides of Physiology

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The Uniqueness of the Reproductive System • Different structural design of the organs of the reproductive systems – Organs of other systems are exactly alike (except, of course, for the brains of ♂ and ♀ :) ) • Function of the reproductive system is to perpetuate the species; i.e., produce new viable offspring – Function of other systems is to maintain homeostasis of the individual Docsity.com Types of Reproduction • Cellular – used for growth and repair of body’s tissues • Organismal – Asexual - division of parent cell into 2 • New individuals are identical to cell derived from – Sexual - use sex cells (gametes) • New gene assortment in new individual • New individuals are not identical to either parent • Cause of the great diversity seen in plants, animals, protistans, fungi, and monera (bacteria) Docsity.com Development of Testes • Develop in abdominal region near site of future kidneys • Descent – Pass from abdominal cavity through inguinal canal to scrotum – Guided by fibromuscular gubernaculum – Pass through inguinal rings (bilateral oblique passage- ways in the anterior abdominal wall). • Openings in aponeuroses of transverse abdominis, internal and external oblique. • Weak part in abdominal wall. Herniation may occur here. • Cryptorchidism – Failure of one or both of testes to descend into scrotum – Prevents normal sperm development Docsity.com Male Reproductive System • The testes produce sperm – Seminiferous tubules • Pathway of spermatozoa – Epididymis – Ductus (Vas) deferens – Ejaculatory duct – Urethra • Accessory sex glands – Seminal vesicles – Prostate – Bubourethral (Cowper’s) glands • Penis Docsity.com The Scrotum • Sac of skin and superficial fascia that hangs outside the abdominopelvic cavity at the root of the penis • Contains paired testicles separated by a midline septum • Its external positioning keeps the testes 3°C lower than core body temperature (needed for sperm production) – Dartos - smooth muscle that wrinkles scrotal sac – Cremaster muscles pulls sac closer to the body • Extensions of the internal oblique muscle of the abdomen Docsity.com Gamete Formation • Gametogenesis – Process of forming the sex cells of the body – Involves two processes • Spermatogenesis - the formation of sperm • Oogenesis - the formation of oocytes • Every body cell has 23 pr of chromosomes (46) – Each pair is homologous (same size and shape) – The cell is diploid (2n chromosomal number) – One of each pair is maternal in origin (from the egg) – The other is paternal in origin (from the sperm) • Gamete formation is by meiosis, in which the number of chromosomes is halved (from 2n to n) • Gametes only have 23 chromosomes – Contain only one of each pair – The cell is haploid (n chromosomal number) Docsity.com Structure of the Seminiferous Tubule • Composed of Sertoli cells (Nurse cells or Susten- tacular cells – Extend from the basal lamina of the seminiferous tubule to the lumen of the tubule – Bound together with tight junctions • Form an unbroken layer (the blood-testis barrier) • Prevents sperm antigens from escaping through the basal lamina into the blood which in turn prevents antibodies from attacking the developing (non-self) spermatocytes – Divide testes into two compartments • Basal compartment – contains spermatogonia and primary spermatocytes • Adluminal compartment – contains meiotically active cells and the tubule lumen Docsity.com Seminiferous Tubules • Spermatozoa produced in seminiferous tubules. – Each tubule ca. 31 in. long; 800 total tubules which equal approximately > 0.5 mile of tubule/testis (2600 feet) – Formed by sustentacular (Sertoli, nurse) cells • Nourish, protect, modify sperm cells and form a blood- testis barrier and produce hormones – Interstitial cells (cells of Leydig) produce testosterone • Lie outside of the seminiferous tubules (in the interstitium) • Sustentacular cells convert testosterone to dihydrotestosterone (DHT) and estrogen. Docsity.com Ducts of the Male Reproductive Tract • Efferent ductules lead out of testis • Epididymis – Elongated tubule with head region, body, and tail regions – Lined by pseudostratified columnar epithelium with stereocilia • Latter increase surface area to facilitate absorption of fluid from lumen of the duct – Site of sperm cell maturation and storage – Takes minimum of 1-2 days • Ductus deferens or vas deferens. Passes from epididymis through inguinal canal into abdominal cavity – Vas deferens, testicular artery and venous plexus, lymphatic vessels, nerves, form the spermatic cord – Distal end of ductus deferens is enlarged as ampulla – Wall of ductus deferens has smooth muscle that undergoes peristalsis as a result of sympathetic innervation during ejaculation • Ejaculatory duct – Joining of ductus deferens and duct of seminal vesicle in the urethra – Ends at urethra within prostate gland Docsity.com Accessory Glands: Seminal Vesicles • Lie on the posterior wall of the bladder and secrete ~60% of the volume of semen – Semen – viscous alkaline fluid containing fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins • Join the vas deferens to form the ejaculatory duct • Sperm and seminal fluid mix in the ejaculatory duct and enter the prostatic urethra during ejaculation Docsity.com Accessory Glands: Prostate Gland • Doughnut-shaped gland that encircles part of the urethra inferior to the bladder • Its milky, slightly acid fluid, which contains citrate, enzymes, and prostate-specific antigen (PSA), accounts for one-third of the semen volume • Plays a role in the activation of sperm • Enters the prostatic urethra during ejaculation Docsity.com Semen • Secretions of all three accessory glands plus sperm cells referred to as semen. • Urethral mucosa produces mucus • Emission: discharge of semen into prostatic urethra • Ejaculation: forceful expulsion of semen from urethra. Caused by peristalsis Docsity.com Testosterone • Most from interstitial cells of testes with small amounts from adrenal glands and sustentacular cells • Causes – enlargement and differentiation of male genitals and reproductive duct system – necessary for sperm cell formation – required for descent of testes – hair growth on certain parts of the body – skin is rougher and coarser – quantity of melanin increases – increases rate of secretion of sebaceous glands – hypertrophy of larynx – increases metabolic rate – increases red blood cell count – increases protein synthesis – rapid bone growth – causes closure of epiphyseal plates Docsity.com Anatomy of Female Reproductive System • Female reproductive organs – Ovaries – Uterine tubes – Uterus – Vagina – External genital organs Docsity.com Maturation and Fertilization of Oocyte • Oogenesis is the production of a secondary oocyte in a major follicle in ovaries • Oogonia are cells from which oocytes develop – Ogoonia divide by mitosis to produce other oogonia and primary oocytes. • Five million oocytes produced by the 4th month of prenatal life. – About 2 million begin first meiotic division but stop at prophase. – All remain at this state until puberty. • Primary oocytes are surrounded by granulosa cells and called a primordial follicle • Primordial follicle becomes a primary follicle when oocyte and granular cells enlarge • Primary follicle becomes secondary follicle and enlarges to form mature or Graafian follicle – Usually only one oocyte is ovulated, others degenerate (atresia) Docsity.com Ovulation, Fertilization, Follicle Fate • Ovulation: release of a secondary oocyte from an ovary. Unlike spermatogenesis, division of cytoplasm during meiosis is uneven and polar bodies are very small, oocyte very large • Graafian follicle become corpus luteum • Fertilization: begins when a sperm cell binds the plasma membrane of secondary oocytes and penetrates into cytoplasm. • Secondary oocyte completes meiosis II forming one polar body. Fertilized egg now a zygote • Fate of corpus luteum – If fertilization occurs, corpus luteum persists – If no fertilization, becomes corpus albicans Docsity.com Follicle Development (Copyrigit® The MeGraic4| Gompaniek. ine, Parmiasion eequitad Yor rapteduetion or Sapte =e Primary ‘ollie Docsity.com Uterus • Major anatomical landmarks – Body – Fundus – Isthmus – Cervix – Cervical os (internal orifice) – Uterine cavity – Cervical canal – Internal os (internal orifice) Docsity.com Uterus • Composed of 3 layers – Perimetrium: Outermost, serous membrane, continuation of the visceral peritoneum – Myometrium: Middle layer of smooth muscle – Endometrium: Thin inner, glandular mucous membrane lining the uterine cavity • Contains simple tubular glands • Functional layer: innermost. Replaced monthly during menstrual cycle • Basal layer: deepest • Cervix. More rigid and less contractile than rest of uterus – Cervical canal. Lined with mucous glands. Glands secrete mucus that covers the external os and blocks sperm entry except during midcycle Docsity.com Endometrium • Has numerous uterine glands that change in length as the endometrial thickness changes • Stratum functionalis: – Undergoes cyclic changes in response to ovarian hormones – Is shed during menstruation • Stratum basalis: – Forms a new functionalis after menstruation ends – Does not respond to ovarian hormones Docsity.com Supports of the Uterus • Mesometrium – portion of the broad ligament that supports the uterus laterally • Uterosacral ligaments – paired ligaments that secure the uterus to the sacrum • Round ligaments – bind the anterior wall to the labia majora Docsity.com Vagina • Major functions – Female organ of copulation – Provides a passageway for birth – Passageway for elimination of menstrual flow • Lies between the bladder and the rectum, extending from the cervix to the exterior of the body • Muscular walls with mucous membrane lining (moist stratified squamous epithelium). • Longitudinal columns and transverse rugae • Fornix: superior domed portion attached to sides of cervix Docsity.com External Genitalia: Vulva (Pudendum) • All structures that lie external to the vagina • Components include the: – Mons pubis - round, fatty area overlying the pubic symphysis – Vestibule - space between labia minora into which urethra and vagina open – Labia majora – elongated, hair-covered, fatty skin folds homologous to the male scrotum – Labia minora - hair-free skin folds lying within the labia majora; homologous to the ventral penis Docsity.com Oogenesis • Production of female sex cells by meiosis • In the fetal period, oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients • Primordial follicles appear as oogonia are transformed into primary oocytes • Primary oocytes begin meiosis but stall in prophase I Docsity.com Oogenesis: Puberty • At puberty, one activated primary oocyte produces two haploid cells – The first polar body – The secondary oocyte • The secondary oocyte arrests in metaphase II and is ovulated • If penetrated by sperm the second oocyte completes meiosis II, yielding: – One large ovum (the functional gamete) – A tiny second polar body Docsity.com Mammary Glands • Organs of milk production located within mammae or breasts • Modified sweat glands • Structure – Alveoli lined by milk-secreting cells – Cells surrounded by myoepithelial cells – Alveoli form lobules – Each lobule has a lactiferous duct – Lactiferous ducts drain into the nipple – Cooper’s ligaments support the breasts Docsity.com