Male Reproductive System: Testes and Scrotum

The testes are the primary male sex organs — a pair of ovoid bodies whose job is to manufacture sperm and testosterone. They hang outside the abdominal cavity inside the scrotum, a loose sac of skin, because viable sperm simply cannot develop at the body's normal internal temperature; the scrotum keeps the testes about 2-3 degrees C cooler, acting as a dedicated thermoregulator for spermatogenesis. Internally, each testis is wrapped in a tough fibrous capsule, the tunica albuginea, and divided by internal septa into some 200-250 lobules. Each lobule packs in 2-4 tightly coiled seminiferous tubules, and these tubules alone make up roughly 80% of the testis's substance — they are where sperm are actually produced. The wall of a seminiferous tubule contains two very different cell types working side by side: Sertoli (nurse) cells, tall pyramidal cells that physically nourish the developing sperm right up to maturity and also secrete the hormone inhibin, which dampens sperm production once output is sufficient; and spermatogonia (male germ cells), which divide meiotically to eventually become sperm. Outside the tubules, in the loose connective tissue be …