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Structure of Testes

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Topic updated on 04/22/17 9:40pm



Anatomy
  • Tunica albuginea
    • an unusually thick, dense connective tissue capsule that covers each testis
  • Lobules
    • incomplete connective tissue septa that projects from tunica albuginea divides each testis into lobules
  • Seminiferous tubules
    • lobules consist of seminiferous tubules
    • spermatogenesis occurs in seminiferous tubules
    • seminiferous tubule epithelium contains spermatogenic cells and Sertoli cells

Spermatogenic Cells
  • Found within the seminiferous tubules
  • Spermatogenic cells are organized in poorly defined layers of progressive development between adjacent Sertoli cells
    • most immature spermatogenic cells, spermatogonia, rest on basal lamina 
    • most mature spermatogenic cells, spermatids, attach to apical portion of Sertoli cells and border lumen of seminiferous tubules
    • dividing spermatogenic cells form daughter cells that remain joined by cytoplasmic bridges
Sertoli Cells
  • Function to synthesize and secrete hormones including
    • anti-Müllerian hormone (AMH)
      • released during embryogenesis and inhibits development of Müllerian (paramesonephric) ducts
    •  androgen-binding protein (ABP)
      • released into luminal space of seminiferous tubules, near developing spermatogonia
      • ABP binds testosterone and maintains high local testosterone levels, necessary for spermatogenesis
    • inhibin
      • provides negative-feedback on hypothalamic-pituitary axis and inhibits GnRH, LH, and FSH
      • has more of an effect inhibiting FSH than GnRH or LH
    • other products
      • other products that support developing spermatogonia and support spermatogenesis
  • Sertoli cell junctional Complexes
    • extensive tight junctions bind adjacent Sertoli cells
    • junctional complexes establish 2 epithelial compartments
      • basal compartment
        • occupies space between basal lamina and Sertoli cell - Sertoli cell junctional complexes
        • contains spermatogonia
      • luminal compartment
        • occupies space above Sertoli cell - Sertoli cell junctional complexes
        • contains primary spermatocytes, secondary spermatocytes, spermatids, and spermatozoa
    •  blood-testis barrier
      • established by junctional complexes
      • spermatogenic cells differ antigenically from somatic cells;therefore, a blood-testis barrier is required to prevent spermatogenic cell exposure to immune system and a resulting autoimmune response


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