Anatomy of the Testis

The Testis

• The testis is surrounded by a dense connective tissue capsule called the tunica albuginea.
• The tunica albuginea divides the testis into approximately 250 pyramidal compartments or testicular lobules.
• Each lobule contains:
  • Connective tissue with endocrine interstitial cells (Leydig cells) that secrete testosterone.
  • One to four highly convoluted seminiferous tubules where sperm production occurs.

Functions of the Testis

• Production of spermatozoa.
• Production of male sex hormones, mainly testosterone.

Germinal Epithelium

• The germinal epithelium is primarily composed of sex cells and a few supporting cells (Sertoli cells).
• The cells lie on a basement membrane surrounded by a connective tissue sheath.

Sex Cells (Spermatogenic Cells)

• Form 4-8 layers in the seminiferous tubules.
• Differentiate progressively from the base to the lumen of the seminiferous tubule.
• Cells include:
  • Spermatogonia
  • Primary spermatocytes
  • Secondary spermatocytes
  • Spermatids
• These cells change to spermatozoa through spermiogenesis.

Sertoli Cells

• Tall columnar cells with bases resting on the basement membrane.
• Apical cell membranes are highly folded and project into the lumina of the seminiferous tubules.
• Cells have pale irregular nuclei with a large nucleolus.
• Lateral cell membranes of adjacent Sertoli cells form occluding junctions, establishing a blood-testis barrier.

Functions of Sertoli Cells

• Provide physical and nutritional support to developing germ cells.
• Perform phagocytosis of cytoplasm eliminated during spermiogenesis.
• Establish a blood-testis barrier by forming zonulae occludentes between adjacent Sertoli cells.

Interstitial Connective Tissue

• Loose connective tissue containing macrophages, fibroblasts, and mast cells.