Male reproduction 2

• Sperm problem?

  • sperm must travel from me seminiferous tubule to female oviduct to fertilise oocyte - very far
  • Female tract is an inhospitable environment
  • Only 1 in 1 million sperm reach the oocyte
• Travel to the epididymis

  • sperm released from associated sertoli cells into seminiferous tubules
  • sperm transported in fluid secreted by Sertoli cells into rete testis, vasa efferentia and finally into the epididymis
• epididymis structure

  • caput - head

  fluid from Sertoli cells reabsorbed here , sperm concentration now 100-fold, sperm is subsequently transported by muscles in epididymis

  • corpus - body

  Modification of environment +sperm maturation

  • cauda- tail

  Sperm stored here - also stored in the vas deferens

  Passage through the epididymis takes 10 days
• Epididymal maturation - sperm structure changes 


  • loss of surplus cytoplasm (cytoplasmic droplet)
  • Condensation o nuclear chromatin by disulphide bridges - makes sperm less likely to be damaged in female reproductive tract
• epididymis maturation - sperm membrane changes 


  • adds surface glycoproteins - decapacitation factors) to plasma membrane- sperm head
  • membrane fluidity and lipid composition change- less susceptible to damage
  • cholesterol selectively metabolised - shifting balance towards unsaturated fatty acids
• metabolism changes sperm undergo in the epididymis 


  • depression (reduction) of metabolic activity to prolong life of cell
  • increased dependence on external fructose for energy production
• Motility changes sperm undergo in the epididymis

  • most important as it allows sperm to swim on their own
  • cAMP content of tail increases allowing acquisition of motility.
• epididymis function 


  • store sperm
  • everything done in the epididymis is preparing sperm for its journey along the reproductive tract
• seminal plasma - bull 


  • sperm ejaculated in seminal plasma
  • seminal plasma derived from accessory secretory glands / vesicles =
  • prostate gland, ampulla, seminal vesicle, bulbourethral
  • seminal plasma determines ejaculate volume not testes
• accessory gland structure varies between species

  dogs - prostate contributes all seminal plasma

  bull - ampulla, seminal vesicle and prostate contribute.

  stallion - ampulla, seminal vesicle and postage contibute

  boar- seminal vesicle and prostate contribute
• ejaculate volume in various species

  bull - 2-10ml

  dog- 2-15ml

  boar- 150-500ml

  horse 30-300ml
• composition of seminal plasma 


  • glycoprotein decapacitation factors
  • fructose and sorbitol - energy substrate
  • citric acid- stops cell coagulation - seminal stones
  • acid phosphates - phospholipid metabolism
  • buffers - neutralise acid pH of vaginal fluids
  • ascorbic acid - reducing agent to protect against sperm oxidation at ejaculation
  • postaglandins - stimulate muscle contractions in female tract - draws sperm up into female tract
• Label the structures

  
• Accessory glands in various animals

  some animas lack accessory glands to rely on other glands to produce seminal plasma

  Eg- dog only has prostate

  Boar lacks ampulla

  Bull and stallion contain all 3 accessory gland structure s