Male Infertility 2

Question 1

What are the endocrine and exocrine functions of the testes?

Answer 1

• Endocrine Testis Function
  
  • Testosterone 5 grams/day produced
  • “Free” Testosterone (Unbound): 2% of the total; biologically active fraction
  • “Bound” Testosterone: 98% of the total; albumin and SHBG
  • Testosterone metabolized to Dihydrotestosterone and Estradiol
• Exocrine Testis Function
  
  • FSH effects on Sertoli Cells
  • Drives production of numerous secreted agents that drive spermatogenesis (androgen binding protein, transferrin, lactate, clusterin, ceruloplasmin).
  • These agents stimulate seminiferous tubule growth and development.
  • They also drive initiation of spermatogenesis during puberty

Question 2

What is the role of Sertoli cells in spermatogenesis?

Answer 2

• Sertoli Cells sit on the seminiferous tubule membrane and extend to the lumen of the seminiferous tubule
• Sertoli cells linked by tight junctions - basis of the blood-testis barrier
  
  • The testis is thus an immunologically privileged site as a result
• Sertoli cells nurse the developing sperm, which progress from the basement membrane to lumen
  
  • Forms microenvironment in which meiosis occurs

Question 3

What is the role of germ cells in male spermatogenesis?

Answer 3

• Germ cell stem cells are arranged on the basement membrane of the seminiferous tubule
• These cells progress through development from basement membrane to lumen
  
  • Spermatogonia (Dark Type A [Ad], Pale type A [Ap], Type B)
  • Primary spermatocytes (preleptotene, leptotene, zygotene, pachytene)
  • Secondary spermatocytes
  • Spermatids (Sa, Sb, Sc, Sd1,and Sd2)