hormones

• endocrine glands release hormones into extracellular fluid surround cell of glands which pass into capillaries and transported by blood until it reaches the target organ
• Pituitary gland secretes hormones that affect parts of reproductive system called gonadotropic hormones
• Follicle-stimulating hormone (FSH)

  Females - 

  • Stimulates development and maturation of ovarian follicle
  • During development, ovarian follicle secretes oestrogen
  • Secretion of FSH decrease as oestrogen increase in blood

  Male - 

  • Stimulates epithelial tissue of seminiferous tubules to produce sperm 
• Luteinising hormone (LH)

  Female -

  • Promotes final maturation of ovarian follicle, ovulation and formation of corpus luteum
  • Corpus luteum secretes progesterone and oestrogen
  • Gradual reduction in LH as progesterone increase in blood

  Male -

  • Stimulates cells in testes to secrete testosterone 
  • Important for development of immature cells into spermatozoa 
  • Major role in maintenance of reproductive organs and sex drive 
• Prolactin

  • direct effect on breasts 
  • with other hormones, important in preparation and maintenance of milk production 
• Oxytocin

  • causes uterine contractions
  • promotes movement of milk 
  • role in movement of sperm and production of testosterone
• Ovarian cycle : A series of events that take place within the ovaries including the maturation of an egg and its release into the uterine tube. Associated with the development of a follicle and formation of corpus luteum
• During first half (10-14 days), levels of FSH and LH increase slowly, promoting growth and maturation of follicle 

  1. Cells forming wall of primary follicle begin to enlarge and divide, create layer of cells around developing oocyte 
  2. Secretions from cells create a fluid-filled space that gradually forces the oocyte to the edge of follicle - secondary follicle 
  3. As more fluid accumulates, follicle continues to enlarge and gradually moves towards the surface of the ovary 
  4. Follicle produces bulge that looks like a swollen blister on surface of ovary - mature follicle 
• Oestrogen and low levels of progesterone are released as follicle grows

  • Around day 14, oestrogen level high enough to stimulate spike in LH and FSH
  • Causes ovulation of most mature follicle 
  • Other follicles degenerate, releasing less oestrogen 
• At ovulation, mature follicle bursts and expels oocyte. Beating cilia creates current that sweeps egg into uterine tube
• Ruptured follicle collapses and blood within forms clot 

  • Clot is gradually absorbed by remaining follicle cells 
  • Follicle cells enlarge and change colour to form cream-coloured body called corpus luteum 

  Corpus luteum secretes oestrogen and progesterone 

  • Progesterone influences development of lining of uterus, preparing for implantation if fertilisation occurs and inhibits release of FSH and LH, preventing other follicles developing 
• If no fertilisation, corpus luteum reaches maximum development 8-10 days after ovulation 

  Begins to degenerate into fibrous mass of scar tissue (corpus albican)

  • Eventually disappears 

  Another ovarian cycle beings due to reduction of progesterone and oestrogen 
• If fertilisation occurs, corpus luteum continues to develop and ovarian cycle cease 

  Corpus luteum is maintained by human chorionic gonadotropin (HCG)

  • Produced by placenta 

  Once placenta can secrete oestrogen and progesterone, corpus luteum begins to disintegrate 

  • Slow, still present in ovary at birth 

  Ovarian cycle resumes after breastfeeding has ceased
• Menstrual cycle 

  Series of changes in the uterine lining in preparation for a developing embryo 
• First stage, while follicle is maturing : 

  Progesterone causes endometrium to become thicker and softer 

  Increase in number of blood vessels and mucus-secreting glands
• After ovulation : 

  Endometrium continues to thicken

  Glands within begin to secrete watery mucus rich in glycogen
• If egg is not fertilised : 

  Corpus luteum degenerates, reducing amount of progesterone 

  • Breakdown of endometrium 
• 14 days after ovulation : Blood from broken-down capillaries, mucous secretions and cell debris from uterine lining are lost through the vagina (menstruation) 
• Secondary sexual characteristics 

  Characteristics associated with person’s sex but not directly involved in sexual reproduction 

  
  

  In Females : 

  Enlarging breasts

  Broadening hips + more rounded contours of body 

  • Growth of pelvic bones
  • Deposition of fat 

  Hair 

  • Straight and light coloured → thicker, curlier, darker covering 

  In Males : 

  Hair on face, chest, back 

  Increase size of larynx - deepening voice