THE REPRODUCTIVE SYSTEM

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THE REPRODUCTIVE SYSTEM

  1. 1. The Reproductive System
  2. 2. Similarities and differences between males and females, but same goal: new life Primary sex organs: gonads  Testes in males  Ovaries in females  These produce the gametes (sex cells)  Sperm in males  Ovum (egg) in females  Endocrine function also: secretion of hormones Accessory sex organs  Internal glands and ducts  External genitalia 2
  3. 3. Male reproductive system Testes (singular testis) or testicles: the gonads  In embryo, first develop in posterior abdominal wall, then migrate  Internal body temp too hot for viable sperm  Temp cooler in the scrotum because of superficial position 3
  4. 4.  Scrotum (=pouch) has septum dividing it Each testis is about 2.5cm x 4 cm in size, within scrotum Dartos and cremaster muscles move testes in response to hot or cold Serous sac partially encloses each testis: the tunica vaginalis*  Develops as outpocketing of peritoneal cavity Just deep to tunica vaginalis is tunica albuginea* - fibrous capsule  Septal extensions of it divide testis into 250-300 lobules  Each lobule contains 1-4 coiled seminiferous tubules: make sperm * * 4
  5. 5.  Just deep to tunica vaginalis is tunica albuginea* - fibrous capsule  Septal extensions of it divide testis into 250-300 lobules*  Each lobule contains 1-4 coiled seminiferous tubules*: make sperm  Converge to form straight tube (tubulus rectus), then conveys sperm into rete testis  Sperm leave testis through efferent ductules which enter epididymis*  Blood supply: pampiniform plexus: from L2 not pelvic level, since descended from abdomen Pampiniform plexus epididymis* * ** * ** (lateral views) * Epididymis is comma-shaped 5
  6. 6. Spermatogenesis: Cross section of seminiferous tubule sperm formation Begins at puberty 400 million sperm/day For baby not to end up with twice as many chromosomes as the parents, the sperm (as well as the egg) needs to have only half (1n) the # of chromosomes (1 of each of the 23) (2n means 2 of each chromosome, one from each parent, totaling 23 pairs = 46 chromosomes) Three stages:  Formation of spermatocytes  Meiosis  Spermiogenesis 6
  7. 7.  1st stage: formation of Cross section of seminiferous spermatocytes tubule  Spermatogonia are stem cells  Least differentiated (earliest in the process)  Lie in basal lamina  Divide continuously by mitosis (result 2n or diploid): daughter cells A (remains a stem cell) or B (goes on)  When start to undergo meiosis are by definition called spermatocytes 2nd stage: meiosis I  Each primary spermatocytes (2n) undergoes meiosis I to become 2 secondary spermatocytes:  Each secondary spermatocyte undergoes meiosis II to become 2 spermatids  Therefore 4 total spermatids from each spermatogonium 3rd stage: spermiogenesis  Spermatids differentiate into sperm 7
  8. 8. Stage 3: Spermiogenesis: spermatid streamlined to sperm  Head contains  Nucleus with chromatid (genetic material)  Acrosome with enzymes for penetrating egg  Midpiece: mitochondria spiraled around the core of the tail  Tail is an elaborate flagellum (allows sperm to swim) know these parts 8
  9. 9.  Sperm can swim only after they have left the * testis Process of spermatogenesis is controlled by two hormones  FSH (follicle stimulating hormones) from anterior pituitary  Testosterone  primary male hormone  produces by testes Sperm surrounded by Sertoli* (sustenacular) cells: tight junctions  Prevents escape of unique antigens seen as foreign  These would activate the immune system  Autoimmune response would cause sterility  Other functions as well Interstitial or Leydig cells: secrete androgens  Male sex hormones  Main one is testosterone  Into blood, sustain all male sex characteristic and sex organs 9
  10. 10.  Sperm leave testis though efferent ductules  Lined by simple columnar epithelium  Cilia and smooth muscle in wall help move sperm along Sperm mature in epididymus (20 days)  Head of epididymus contains the efferent ductules which empty into duct of the epididymus  Sperm gain ability to swim  Sperm can be stored in epididymus for several months(reabsorbs fluid) Duct of epididymis: highly coiled 6m long duct (pic left is multiple coils of same duct) *Note pseudostratified* columnar epithelium Ductus (vas) deferens: note thick layers of smooth muscle 10
  11. 11.  Sperm are ejaculated from the epididymus  Not directly from the testes Vas deferens* (or ductus deferens) 45cm (18”)  Stores and transports sperm during ejaculation  Runs superiorly from scrotum within spermatic cord, through inguinal canal and enters pelvis  Histo: see previous slide •Vas* arches medially over ureter •Descends along posterior wall of bladder •Ends in ampulla which joins duct of * seminal vesicle to form short ejaculatory duct •Each ejaculatory duct runs within prostate where empties into prostatic urethra 11
  12. 12. Inguinal hernia Spermatic cord: • Vas deference is the largest component • Is a tube of fascia also containing nerves and vessels • Runs in inguinal canal Inguinal canal has 2 rings: 1. Superficial (medial) 2. Deep 12
  13. 13. Posterior view Lateral view  Seminal vesicles  On posterior bladder  Secrete fluids and substances which constitute 60% of semen  Their ducts join vas deferens  Sperm and seminal fluid mix in ejaculatory duct  Prostate: note here and next slide  Bulbourethral glands  Secrete mucus during sexual excitement and ejaculation 13 (lubricant)
  14. 14. The Prostate Size & shape of a chestnut Encircles 1st part of urethra 3 types of glands  Contribute to semen (milky fluid and enzymes)  PSA measured as indicator of prostate cancer (“prostate specific antigen”) Fibromuscular stroma 14
  15. 15. Posterior view  Male external genitalia  Scrotum  Penis  Penis: 3 parts  Root (attached)  Free shaft or body  Enlarged tip called glans penis  Skin of penis is loose  Prepuce or foreskin  Cuff around glans  Removed if circumcision  See cross section, penis  Urethra (called spongy or penile urethra here)  3 erectile bodies (parasympathetic stimulation during sexual excitation causes engorgement with blood allowing erection):  Corpus spongiosum  Pair of corpora cavernosa  Vessels and nerves  Ejaculation caused by sympathetic nerves  Contraction of smooth muscle of ducts and penis 15
  16. 16. Review pics 16
  17. 17. The Female Reproductive System Production of gametes (ova, or eggs) Preparation for support of developing embryo during pregnancy Cyclic changes: menstrual cycle  Averages 28 days  Complex interplay between hormones and organs: at level of brain, ovaries and uterus 17
  18. 18.  Gonads: the ovaries  Paired, almond-shaped, flanking the uterus in lateral wall of true pelvis  3 x 1.5 x 1 cm in size Posterior view 18
  19. 19. Anterior view Ovaries are retroperitoneal, but surrounded by peritoneal cavity Held in place by mesentery and ligaments: •Broad ligament •Suspensory ligament of the ovary •Ovarian ligament Innervation: •Sympathetic and parasympathetic 19
  20. 20. Structure of ovary Fibrous capsule is called tunica albuginea Outer cortex houses developing gametes the oocytes, within follicles Inner medulla is loose connective tissue with largest vessels and nerves 20
  21. 21. The Ovarian Cycle Follicular phase  1st approx 14 days but variable  Egg develops in a follicle  Stimulated by FSH (see next slide)  Estrogen produced Ovulation  Egg released from follicle (LH surge)  Egg in abdominal cavity  Picked up by fimbria of fallopian tube  Not necessarily halfway point Luteal phase  Postovulatory phase 14 days (more constant)  Corpus luteum develops from exploded follicle  Produces progesterone as well as estrogen  Progesterone stimulates uterus to be ready for baby  If no pregnancy, corpus luteum degenerates into corpus 21 albicans
  22. 22. Nearly mature follicle Oocyte develops the zona pellucida  Glycoprotein coat  Protective shell (egg shell)  Sperm must penetrate to fertilize the oocyte Thecal cells stimulated by LH to secrete androgens Granulosa cells (with FSH influence) convert androgens to estrogen (follicular cells called granulosa cells now) Clear liquid gathers to form fluid-filled antrum: now a secondary follicle Surrounding coat of granulosa cells: corona radiata Fully mature, ready to ovulate, called: ”Graafian follicle”22
  23. 23. Ovulation Signal for ovulation is LH surge Ovarian wall ruptures and egg released, surrounded by its corona radiata 23
  24. 24. Oogenesis Generation of eggs Starts in fetal period  No more oocytes made after about 7th month  Developed only to early stage of meiosis I by birth and stops (called primary oocyte) 6-12 primordial oocytes each cycle selected to develop for ovulation (most die)  Only then is meiosis I completed  Secondary oocyte is then arrested in meiosis II Meiosis II not completed (now an ovum) unless sperm penetrates its plasma membrane Of the 4 daughter cells, only one becomes ovum (needs a lot of cytoplasm)  The other 3 become “polar bodies” 24
  25. 25. Fallopian (uterine) tubes, AKA oviducts ____Fallopian tubes__ Fimbriae (fingers) pick up egg Fimbriae * Beating cilia and muscular peristalsis propel egg to uterus Empties into superior part of uterus* Enlargement of mucosa layer showing ciliated columnar epitheliumCross sectionthrough entiretube PID 25
  26. 26. The Uterus (womb) In pelvis anterior to rectum and posterosuperior to bladder Hollow, thick-walled organ  Receives  Retains Uterus is pear-shaped  Nourishes fertilized egg=embryo (before babies) Usually anteverted, can be retroverted 26
  27. 27. Parts of uterus: Body (major part) Fundus Isthmus Cervix Cavity of uterus small (except in pregnancy) Cervical canal •Internal os •External os Vagina Cervix •Tough, fibrous ring •Inferior tip projects into vagina 27 •Produces mucus
  28. 28. The Uterine Wall*  Three basic layers  Perimetrium: outer serous membrane  Myometrium: middle muscle  Endometrium: inner mucosal liningUterinesupports:•Mesometrium(largest divisionof broad lig) – *main support•Cardinalligament•Round ligament(Prolapse) 28
  29. 29. Endometrium (inner mucosal lining of uterine cavity)  Simple columnar epithelium containing secretory and ciliated cells  Lamina propria of connective tissue Note: Uterine glands Uterine arteries2 main layers (Strata)1. Functionalis (functional layer)2. Basalis (basal layer) (shed if no implantation of baby) (not shed) 29
  30. 30. Time: one cycle (approx 28 d.) ovulation *  Pituitary hormones  FSH: follicle stimulating hormone  LH: luteinizing hormoneFollicular phase Luteal phase  Ovarian hormones  Estrogen  Progesterone 30
  31. 31. The cyclic changes of uterine wall and follicle (hormone graphs should be above) If no baby, decreasing progesterone - slough Proliferative Secretory phase: vascular phase: rebuilds rich glands enlarge: will itself after slough sustain baby (needs progesterone: corpus luteum 31 initially then placenta)
  32. 32. (inhibin: inhibits pituitarysecretion of FSH) 32
  33. 33. The Vagina Thin-walled tube Inferior to uterus Anterior to rectum Posterior to urethra & bladder “Birth canal” Highly distensible wall: 3 layers  Adventitia  Muscularis  mucosa 33
  34. 34. External female genitalia aka vulva or pudendum Mons pubis: fatty pad over pubic symphysis, with hair after puberty Labia (lips) majora: long fatty hair-covered skin folds Labia minora: thin, hairless, folds enclosing vestibule Vestibule: houses external openings of urethra and vagina  Urethra is anterior (drains urine from bladder)  Baby comes out through vagina (vaginal orifice in pic) Clitoris: anterior, homolog of penis (sensitive erectile tissue) Perineum: diamond shaped region 34
  35. 35. Mammary glands (breasts) Modified sweat glands Both sexes but function (normally) only in lactating female Produce milk to nourish baby Respond to hormonal stimulation Lymph drains into parasternal and axillalry lymph nodes Nipple surrounded by pigmented ring of skin, the areola Muscles underneath: pectoralis major and minor, parts of serratus anterior and external oblique 35
  36. 36.  Mammary glands consist of 15-25 lobes Each a distinct compound alveolar gland opening at the nipple Separated by adipose and suspensory ligaments Smaller lobules composed of tiny alveoli or acini  Like bunches of grapes  Walls: simple cuboidal epithelium of milk-secreting cells  Don’t develop until half-way through pregnancy (ducts grow during puberty) Milk passes from alveoli through progressively larger ducts  Largest: lactiferous ducts, collect milk into sinuses 36
  37. 37. Conception  After ejaculation into the vagina, sperm swim to meet an egg  Sperm live 5-7 days (need cervical mucus)  Eggs live about 12-24 hours, so conception only occurs during this short window  Fertilization occurs in the fallopian tubeEvents leading tofertilization:•Sperm binds to receptors onzona pellucida•Acrosomal reaction –enzymes digest a slit•Sperm passes through zona•Fusion of a single sperm’splasma membrane withoocyte’s plasma membrane•Cortical reaction: spermreceptors destroyed in zonaso no more enter; spermnucleus engulfed by egg’scytoplasmFertilization occursat the moment thechromosomes fromthe male and female 37gametes unite
  38. 38. Initial days Cleavage (cell division) Blastocyst stage by day 4: now in uterus 38
  39. 39. ImplantationBlastocyst floats for 6-9 days post2 days: “hatches”by digesting zona conception -enough to squeeze burrows intoout endometrium 39
  40. 40. Formation of Placenta Both contribute: •Trophoblast from embryo •Endometrial tissue from mother Not called placenta until 4th monthEmbryonicbloodcirculateswithin chorionicvilli, close tobut not mixingwith mother’sblood •Nutrients to baby •Wastes to 40 mom
  41. 41. The “Placental Barrier” Sugars, fats and oxygen diffuse from mother’s blood to fetus Urea and CO2 diffuse from fetus to mother Maternal antibodies actively transported across placenta  Some resistance to disease (passive immunity) Most bacteria are blocked Many viruses can pass including rubella, chickenpox, mono, sometimes HIV Many drugs and toxins pass including alcohol, heroin, mercury Placental secretion of hormones  Progesterone and HCG (human chorionic gonadotropin, the hormone tested for pregnancy): maintain the uterus  Estrogens and CRH (corticotropin releasing hormone): promote labor 41
  42. 42.  Gestational period: averages 266 daysChildbirth  (this is time post conception; 280 days post LMP) Parturition: the act of giving birth: 3 stages of labor 1. Dilation: 6-12h (or more in first child); begins with regular uterine contractions and ends with full dilation of cervix (10cm) 2. Expulsion: full dilation to delivery – minutes up to 2 hours 3. Placental delivery: 15 minutes Dilation of cervis; head enters true pelvis Expulsion: head first safest as is largest part Delivery of the placenta Late dilation with head rotation to AP position 42
  43. 43. Stages of Life Embryologically, males and females start out “sexually indifferent”  Gonads, ducts and externally identical structures  At 5 weeks gestation changes start to take place Puberty: reproductive organs grow to adult size and reproduction becomes possible  Between 10 and 15  Influence of rising levels of gonadal hormones  Testosterone in males  Estrogen in females Female menopause (between 46 and 54):  Loss of ovulation and fertility 43
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