Reproductive

• Reproductive system


  All organs involved in mating, gametogenesis, or other functions involved in producing offspring
• Components of the reproductive system

  • Gonads
  • Accessory reproductive organs
• Gonads

  Male: testes

  Female: ovaries
• Functions of gonads

  • Produce gametes

  Secrete sex hormones
• Male reproductive organs


  • Seminal vesicle

  Ejaculatory duct

  Prostate gland

  Bulbourethral gland

  Epididymis

  Scrotum

  Testis

  Penis

  Erectile tissue

  Urethra

  Vas deferens
• Testes

  250-300 compartments that contain seminiferous tubules where sperm production occurs
• Seminiferous tubules


  • Sertoli cells (epithelial cells) found in the tubules: support sperm development

  Leydig cells (interstitial cells) found in between tubules: secrete testosterone
• Sperm development in seminiferous tubules


  Sperm cells located in the space between the Sertoli cells during development

  Once developed, sperm cells move to the lumen of the tubules

  
• Seminiferous tubule structure


  • Basal compartment

  Lumenal compartment

  Smooth muscle around the tubules: peristalsis propels sperm

  Blood-testis barrier: tight junctions isolate lumenal fluid from compartment fluid, promote sperm nourishment, prevent immune attack
• Sertoli cells


  Support sperm development

  Secrete lumenal fluid in which sperm develop

  Secrete androgen-binding protein (androgen buffer)

  Target cells to testosterone and FSH

  Secrete chemicals that stimulate spermatogenesis

  Secrete inhibin (negative feedback for FSH)
• Hormonal regulation of male reproductive function


  GnRH secretion from hypothalamus

  FSH and LH secretion from anterior pituitary

  Testosterone secretion from Leydig cells

  Inhibin secretion from Sertoli cells (negative feedback for FSH)

  
• Testosterone


  Hormone secreted by Leydig cells that is essential for spermatogenesis and male sexual characteristics
• Sperm structure


  • Head: chromosomes, acrosome (enzymes for fertilization)

  Midpiece: mitochondria

  Tail: whiplike movements propel sperm
• Spermatogenesis


  Spermatogonia (2n) -> Primary spermatocytes (2n) -> Secondary spermatocytes (n) -> Spermatids (n) -> Spermatozoa (n)

  Occurs from basement membrane to lumen of seminiferous tubules
• Sperm maturation


  Spermatozoa released into lumen of seminiferous tubules, remain immotile for 20 days

  Move to epididymis by peristalsis and fluid flow, acquire motility

  Move to vas deferens by peristalsis, remain until ejaculation
• The female reproductive system differs from the male in having cyclic changes in activity, restricted periods of fertility, and limited gamete production
• Female reproductive organs


  • Uterine tube

  Ovary

  Fimbriae

  Uterus

  Vagina

  
• Follicles


  Found in the ovaries, undergo major development from primordial to Graafian follicle

  Oocyte supported by granulosa cells, some of which become theca cells

  
• Granulosa cells


  • Target cells for hormones like estrogen and FSH

  Secrete chemical messengers, inhibin, estrogen, and progesterone

  Transport nutrients to oocytes
• Uterine tube


  Site of fertilization, movement of ovum to uterus by peristalsis and ciliary action (4 days)

  
• Oogenesis


  Oogonia -> Primary oocyte (2n) -> Meiosis I -> Secondary oocyte (n) -> Meiosis II after fertilization

  
• Hormonal regulation of female reproductive function


  GnRH, FSH, LH, inhibin, estrogen, progesterone all play roles

  
• The menstrual cycle


  Ovarian cycle (follicular phase, luteal phase)

  Uterine cycle (menstrual, proliferative, secretory phases)

  
• Follicular phase


  FSH and estrogens stimulate follicle growth and development

  A few follicles develop from primordial follicles

  Oocyte grows, granulosa cells proliferate and form zona pellucida

  
• Ovulation


  Graafian follicle ruptures, releasing oocyte and antral fluid

  Ruptured follicle becomes corpus luteum that secretes estrogen and progesterone

  
• Luteal phase


  Begins at ovulation, corpus luteum secretes estrogen and progesterone

  
• The menstrual cycle lasts approximately 28 days, with the follicular phase lasting 14 days and the luteal phase lasting 14 days
• Antrum


  • Continues to expand
  • Follicle grows to about 2-2.5 cm in diameter just before ovulation
• Ovarian cyst


  What happens when ovulation does not occur

  
• Stages of follicle development


  • Primordial follicle
  • Primary follicle
  • Secondary follicle
  • Graafian follicle
• Graafian follicle


  • Contains antrum
  • Contains corona radiata
  • Contains oocyte
  • Contains cumulus oophorus
  • Contains theca cells
  • Contains granulosa cells

  
• Stages of the menstrual cycle


  • Menstrual phase
  • Proliferative phase
  • Secretory phase
  • Luteal phase
  • Follicular phase

  
• Ovulation


  1. Graafian follicle ruptures

  2. Antral fluid with oocyte flows to ovary surface

  3. Oocyte is released and enters fimbriae

  
• Corpus luteum


  Gland formed from ruptured follicle that secretes estrogen and progesterone
• Corpus albicans


  What the corpus luteum becomes when it degenerates
• Ovulation and corpus luteum formation is triggered by the same events (LH surge)

  
• Menstrual phase


  1. Blood vessels constrict

  2. Underlying tissue dies and separates from endometrium

  3. Menstrual flow occurs

  
• Proliferative phase


  • Uterus renews itself
  • More hospitable to sperm
• Secretory phase


  • Endometrium grows and transforms to be hospitable for implantation
  • Lots of secretion to make uterus sticky
• If fertilization occurs


  Corpus luteum does not degenerate and estrogen and progesterone remain high