REPRODUCTIVE SYSTEM

• Reproductive system


  Organ system with anatomic differences between males and females

  
• Gametogenesis


  Production of male (spermatogenesis) and female (oogenesis) gametes
• Testes


  • Organs that produce male gametes (sperm) and testosterone
  • Pair of oval bodies lodged in the scrotum
  • Each is 4-5 cm long, 3 cm wide and 2 cm thick and weighs about 14g
  • Enclosed by a tough fibrous capsule called TUNICA ALBUGINEA (Dense Irregular C.T)
• Spermatogenesis


  1. Spermatogonia (small, round stem cells located next to basal lamina)

  2. Primary spermatocytes (larger, located more towards lumen)

  3. Secondary spermatocytes (short-lived; hard to see)

  4. Spermatids (close to lumen; sperm precursors)
• Interstitial cells of Leydig


  • In connective tissue between seminiferous tubules
  • Usually present in clusters
  • Produce testosterone
• Sertoli cells


  • Form tight junctions: "blood-testis barrier"
  • Provide support, protection, and nutrition for developing sperm
  • Produce fluid in lumen of seminiferous tubules
  • Secrete hormones that facilitate spermatogenesis
• Fertilization


  1. Acrosome contains hydrolytic enzymes

  2. Acrosomal reaction causes dissociation of cells of corona radiata and digestion of zona pellucida surrounding the oocyte
• Seminal vesicle


  • Really a diverticulum of the distal end of the vas
  • Highly coiled duct surrounded by 2 layers of smooth muscle that expel luminal contents during ejaculation
  • Intricately folded mucosa with secretory vesicles that produce fluid comprising most of volume of ejaculate
  • Rich in fructose (energy drink for sperm)
• Prostate


  • Produces thin, milky fluid containing lipids and enzymes
  • Fluid comprises about 25% of seminal fluid
  • Three zones of glands: peripheral, central and transitional (all empty into prostatic urethra)
  • Peripheral zone is largest and most common site of prostatic carcinoma
• Bulbourethral glands


  • Paired glands also known as Cowper's glands
  • About the size of peas
  • Secrete clear viscous material to lubricate the penile urethra
• Semen


  • 1.5 – 3 ml per ejaculate
  • 40 – 300 MILLION spermatozoa per milliliter
  • Epididymal, seminal vesicle and prostatic secretions
• Penis


  • Three cylindrical bodies of erectile tissue (irregular vascular spaces, collapsed in flaccid state)
  • Two corpora cavernosa (dorsally situated)
  • Corpus spongiosum (ventrally situated)
  • Arteries (smooth muscle occludes lumens when there is muscle tone) open into cavernous spaces
  • Venules drain cavernous spaces
  • Tunica albuginea (sheath: fibrous around cavernosa, elastic around spongiosum)
• Ovulation


  1. FSH from anterior pituitary stimulates growth of ovarian follicles

  2. Growing ovarian follicles secrete increasing levels of estrogen, precipitating a surge of LH from anterior pituitary on day 14

  3. LH causes rupture of follicle and release of oocyte
• Corpus luteum


  • Granulosa cells and theca interna cells of ovulated follicle turn into a temporary endocrine organ
  • LH causes granulosa cells to differentiate into granulosa lutein cells and theca interna cells to differentiate into theca lutein cells
  • Both new cell types produce progesterone and estrogen
• Types of corpus luteum

  • Corpus luteum of menstruation
  • Corpus luteum of pregnancy
• Menstruation


  1. Degeneration of the corpus luteum results in loss of estrogen and progesterone production

  2. Constriction of spiral arteries in uterus causes ischemia and tissue necrosis in the upper layer of the endometrium

  3. Blood and necrotic tissue are released

  4. Bottom layer remains viable and regenerates endometrial glands during the next cycle under influence of estrogen
• Phases of the menstrual cycle

  • Menstrual phase (days 1-5)
  • Proliferative phase (days 6-14)
  • Secretory phase (days 14-28)
• Cervical transformation zone


  • Abrupt change from simple columnar to stratified squamous epithelium
  • Ectocervix is squamous, endocervix is columnar
  • Exact location changes with age