Spermatogenesis Flashcards

1
Q

Testicular anatomy

A
  • Spermatogenesis occurs in seminiferous tubules
  • Rete testis receives drainage from seminiferous tubules
  • Rete testis empties into epididymis
  • Epididymis function is to store sperm, help sperm mature, has 3 regions
    • Head: concentration
    • Body: maturation
    • Tail: storage
  • Spermatogenesis occurs from basement membrane inward to seminiferous tubule lumen
  • Blood-testis barrier formed by tight junctions between Sertoli cells
    • Physical barrier between blood vessels and seminiferous tubules
    • Prevents some proteins and toxic agents from entering seminiferous tubules
    • Differentiating germ cells (with 1N haploid DNA) are potentially antigenic/recognizable as foreign - barrier sequesters these cells from the blood environment
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2
Q

Spermatogenesis and spermiogenesis

A
  • Spermatogenesis occurs in a cyclical fashion that is continuous: at any given time or place in the seminiferous vesicle, different stages of spermatogenesis will be seen (about 60 different stages in humans)
  • Defined as 3 stage process by which spermatogonial stem cells give rise to spermatozoon:
    • Proliferative phase: spermatogonia mitotically divide = 1 primary spermatocyte + 1 copy of self
    • Meiotic phase: spermatocytes undergo meiosis that reduce the chromosome number by half
    • Spermiogenic phase / spermiogenesis: haploid spermatid differentiated into mature spermatozoa
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3
Q

Spermiogenesis

A
  • Haploid spermatid differentiated into mature spermatozoa
    • Golgi phase = G apparatus produces acrosomal vesicles - most prominent cytoplasmic inclusion
    • Cap phase = acrosomal vesicle migrate to one end of spermatid, capping sperm
    • Acrosomal phase
    • Maturational phase
  • Spermiation is final step of spermatogenesis in Sertoli cell, in which sperm is released from Sertoli cell into the epididymis (via rete testis)
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4
Q

Functions of Leydig (interstitial) cells

A
  • Produce androgens including 95% of testosterone; stimulated to do so by LH
  • T synergizes with FSH to stimulate formation of ABP in Sertoli cells
  • Synthesis of StAR, SCP, SAP
    • Help cholesterol get into cell and make steroids
  • Required for spermiogenesis
  • Have LH receptors (Gs)
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5
Q

Functions of Sertoli (supporting) cells

A
  • Form blood testis barrier via tight juntions
  • Produce ABP - dramatically increase effectiveness of testosterone
  • Nurture gametes (47 spermatozoa per Sertoli cell)
  • Have FSH receptors (Gs)
    • Produces estrogens from T via aromatase
    • Produces inhibin and other growth factors
  • Support Leydig cells with other growth factors + inhibin
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6
Q

Hormonal control of spermatogenesis

A
  • Spermatogenesis stimulated by testosterone, under control of HPT axis
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