development of reproductive system

• genotype determines what gonads you get
• hormones control external and internal anatomy
• sex assignment based on external anatomy
• germ cells migrate from yolk sac into

  urogenital ridge
• urogenital ridge makes 


  urinary system and gonads (initial sex differentiation)
• ovaries are oestrogen based system
• testes are testosterone based system
• all embryos start with bipotential
• hormonal exposure leads to maintenance and degeneration of structures
• metanephric kidney is final kidney that is developed 


  tubes from it develop to become part of the reproductive system
• oestrogen maintains paramesonephric duct
• lack of testosterone leads to degeneration of mesonephric duct
• at week 20 lack of testosterone leads to degeneration of duct
• in males, at week 16, anti-Mullerian hormone stimulated degeneration of paramesonephric duct, mesonephric duct becomes epididymis and vas deferens
• 7 weeks is 9 weeks since last menstrual period
• XX external differentiation

  • genital tubercle becomes clitoris
  • genital fold becomes labia minora and urethra and vaginal orifices
  • genital swelling becomes labia majora
• XY external differentiation

  • genital tubercle becomes the glans penis
  • genital fold forms urethral fold and raphe
  • genital swelling forms the scrotum
• external differentiation

  labels

  A) labia majora

  B) labia minora

  C) clitoris

  D) vagina

  E) glans penis

  F) urethral raphe

  G) scrotum

  
• XY growth of external differentiation is stimulated by production of

  dihydrotestosterone
• androgens are 


  testosterones from testes and adrenal cortex
• oestrogens 


  ovaries, placenta and testosterone
• progestins 


  ovaries and placenta
• sex steroids are made from

  cholesterols
• XX and XY systems use same hormones but different forms and function in the body depending on 


  quantity, structures and receptors and mediators
• initiation of reproductive cycle

  • GnRH is released from hypothalamus as brain matures
  • gonadotrophins are released from the anterior pituitary

  LH and FSH stimulate gonadal development and released of testosterone, oestrogen and progesterone

  • hormones cause growth and secondary sex characteristics
• hormones are controlled by negative feedback
• female reproductive cycle

  • ovarian -maturation of oocyte
  • uterine - implantation environment is stable
  • cervical - controls sperm entry
• ovary is site of endocrine production and growth factors and regulatory peptides
• female reproduction is influenced by stress more than the male, could be related to up to 50% of cases female infertility
• oocyte meiosis produces one daughter and one polar body (which degrades)
• meiosis II happens after fertilisation and just before 2 nuclei fuse
• ovulation

  • oocytes surrounded by follicular cells
  • supportive and release hormones to drive cycle
  • GnRH stimulates LH and FSH from anterior pituitary
  • FSH stimulates growth of follicular cells
  • LH stimulates cells to produce androgens and ovulation
• uterine cycle has 2 stages

  • follicular (proliferation)
  • luteal (secretive)
• uterine follicular

  • oestrogen increases maturing follicles
  • growth of uterine lining
  • oestrogen stimulates GnRH
• luteal progesterone and oestrogen levels

  • inhibit FSH and LH by inhibin
  • progesterone inhibited by oestrogen
  • progesterone from maturing follicles then from corpus luteum after ovulation
  • progesterone- secretion of nutritive substance to support early pregnancy
• cervical cycle

  • ovulatory and luteal
• cervical cycle (ovulatory)

  • mucus fibres more linear, allow sperm to follow up fibres
  • mucus more fluid and slippery
  • mucus is high in pH to promote sperm survival
  • sperm survive several days (increase fertile window)
• cervical cycle (luteal)

  • progesterone thickens
  • cervical plug
  • pH change
• production of sperm stages

  • A-spermatogonium
  • B-spermatogonium
  • primary spermatocyte
  • secondary spermatocyte
  • spermatid
  • sperm cell (spermatozoon)
• production of sperm can take 65-75 days