spermatogeneesi

Spermatogenesi, or spermatogenesis, is the process by which male gametes, or spermatozoa, are produced in the seminiferous tubules of the testes. It includes mitotic proliferation of spermatogonia, meiotic divisions to form haploid cells, and spermiogenesis, the transformation of spermatids into mature sperm. The process results in genetically diverse, motile sperm capable of fertilization.

The production occurs within the seminiferous epithelium, a multilayered niche organized by Sertoli cells. These somatic cells form a blood–testis barrier that protects developing germ cells and provides structural support, nutrients, and signaling. Germ cells progress from the basal compartment toward the lumen, in a coordinated sequence that ensures continuous sperm production.

Spermatogenesis has three main phases. The spermatogonial phase involves mitotic divisions of spermatogonia, maintaining the stem cell pool and generating type B cells that become primary spermatocytes. The meiotic phase includes Meiosis I, producing two secondary spermatocytes, and Meiosis II, yielding four haploid spermatids per primary spermatocyte. The spermiogenesis phase transforms round haploid spermatids into elongated, motile spermatozoa, with nuclear condensation, acrosome formation, development of a flagellum, and shedding of excess cytoplasm as residual bodies.

Hormonal regulation is essential. FSH stimulates Sertoli cells to support germ cell development, while LH stimulates Leydig cells to produce testosterone. Testosterone, in concert with FSH, drives progression through meiosis and maturation. Inhibin from Sertoli cells provides negative feedback to the pituitary.

In humans, spermatogenesis takes about 64 days, with cohorts at different stages forming a continuous wave along the seminiferous tubules. Mature spermatozoa are released into the tubule lumen and transported to the epididymis for final maturation and storage. Disruptions can affect fertility.