Spermatogenesis: Sperm Production in Seminiferous Tubules

on 20.7.06 with 0 comments



From Spermatogonia to Spermatids (occurs in seminiferous tubules of testes)
basal lamina spermatogonia ("germ cell") -> Type A daughter cell (remains on wall); Type B daughter cell (spermatogenesis) -> primary spermatocyte (meiotic divisions) -> 2 secondary spermatocytes (meiosis I) -> lumen 4 spermatids (each haploid "n")
  • Spermiogenesis: From Spermatid to Spermatozoon
  • acrosome - package of enzymes at top of sperm; allows penetration of the eggs for fertilization
  • nucleus - positioned in "head" of sperm along just behind acrosome; allows for delivery of DNA to egg
  • tail - microtubules arrange into 9+2 configuration to form "flagellum" for locomotion
  • mitochondria - located around the base of the tail; provide ATP for the swimming motion
  • cytoplasm - excess cytoplasm in "sloughed off"
  • The Role of Sustentacular Cells (Antigen Barrier)
  • Sustentacular cells (Sertoli cells) - with tight junctions, divide the seminiferous tubule into "basal compartment" and "adluminal compartment"
  • blood-testis barrier - these cells prevent leakage of proteins from "new genetic cells" (from crossing over) to stimulate an autoimmune response, which would kill the gametes
  • absorb excess cytoplasm "sloughed off"
  • chemical signals that regulate entire process
  • Effects on Spermatogenesis and Fertility
  • Autoimmune disorder - immune system attacks "new" sperm cells which are different from somatic cells due to crossing over during mitosis
  • Other factors: radiation, lead poisoning, some pesticides, marijuana, alcohol can lead to abnormal sperm production
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Category: Physiology Notes

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