Key Points Summary — Male Reproductive System and Spermatogenesis — Summary

The testes are located in the scrotum because spermatogenesis requires a temperature approximately 2–3°C below core body temperature (~35°C vs. 37°C core).
Each testis contains approximately 250 compartments (lobules), each with 1–3 seminiferous tubules.
Sertoli cells (sustentacular): inside seminiferous tubules; nourish developing sperm; form the blood-testis barrier; secrete inhibin (negative feedback on FSH).
Leydig cells (interstitial): in spaces between tubules; secrete testosterone in response to LH.
Spermatogenesis pathway: Spermatogonium (2n) → [mitosis] → Primary spermatocyte (2n) → [meiosis I] → Secondary spermatocyte (n) → [meiosis II] → Spermatid (n) → [spermiogenesis] → Spermatozoon (n).
Yields 4 haploid functional spermatozoa per spermatogonium; takes approximately 64 days.
Sperm structure: Head (acrosome with hydrolytic enzymes + haploid nucleus), Middle piece (mitochondria in helical arrangement → ATP for motility), Tail (flagellum for locomotion).
Accessory glands: Seminal vesicles (fructose-rich, ~60% semen volume) → energy for sperm; Prostate (~30%, alkaline) → neutralizes vaginal acidity; Bulbourethral glands → lubrication.
FSH acts on Sertoli cells (supports spermatogenesis); LH acts on Leydig cells (testosterone synthesis).
Testosterone exerts negative feedback on the hypothalamus-pituitary axis; inhibin exerts negative feedback specifically on FSH.