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Histology · Reproductive system

Testis: seminiferous tubules, Sertoli and Leydig cells, spermatogenesis !

  • Organ

The testis makes sperm in coiled tubes and testosterone in the cells that sit between them.

Updated 2026-11-01

See it in 3D: Testes

What it is

The testis is wrapped by the tunica albuginea and divided into lobules of seminiferous tubules. The seminiferous epithelium holds maturing germ cells and Sertoli cells, which support them and form the blood-testis barrier. Between the tubules, Leydig cells make testosterone. These cells explain male infertility, the risk of cryptorchidism and testicular tumours.

Structure

  • On H&E: round tubules with a many-layered stratified epithelium and sperm tails in the lumen.
  • Sertoli cells: pale, triangular or oval nucleus with a prominent nucleolus, resting on the basement membrane.
  • Primary spermatocytes: the largest cells, with threadlike chromatin from the long prophase of meiosis I.
  • Interstitium: clusters of polygonal, eosinophilic Leydig cells beside capillaries.

Function

  • Make sperm continuously from puberty on.
  • Make testosterone, which keeps spermatogenesis going and maintains male sex characteristics.
  • Hide haploid germ cells from the immune system behind the blood-testis barrier.

Step by step

  1. Spermatogonia, stem cells at the base of the tubule, divide by mitosis and renew their pool.
  2. Some become primary spermatocytes, which cross the blood-testis barrier and begin meiosis I.
  3. Meiosis I makes secondary spermatocytes, which live very briefly.
  4. Meiosis II makes four haploid spermatids from each primary spermatocyte.
  5. In spermiogenesis the spermatid forms the acrosome, condenses its nucleus, builds the flagellum and sheds cytoplasm.
  6. Sperm are released into the lumen and mature in the epididymis; the full cycle takes a little over two months.

Markers

  • Inhibin (Sertoli and Leydig)
  • OCT3/4 and PLAP (seminoma)
  • Serum AFP and hCG (germ cell tumours)

Clinical notes

  • Klinefelter syndrome (47,XXY): hyalinised tubules without spermatogenesis and small testes.
  • Varicocele: extra heat from dilated veins can reduce sperm production.
  • Leydig cell tumours may make androgens or estrogens.

Test yourself

Think of the answer, then tap the question to see it.

Which cells form the blood-testis barrier?

The Sertoli cells, joined to each other by tight junctions.

Which pituitary hormone directly stimulates Leydig cells?

Luteinizing hormone (LH), which drives testosterone production.

What happens in spermiogenesis?

The round spermatid becomes a sperm: it forms the acrosome, condenses the nucleus, builds the flagellum and sheds cytoplasm; there is no cell division.

Why does cryptorchidism impair spermatogenesis?

The testis stays at body temperature, warmer than the seminiferous epithelium needs; it also raises the risk of germ cell tumour.

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Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: 27.1 Anatomy and Physiology of the Testicular Reproductive System (OpenStax, Rice University, 2022); Testes (National Cancer Institute, SEER Training Modules, 2026).

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