The seminiferous tubules consist of a complex stratified epithelium composed of germ cells and Sertoli cells. Between the tubules, the interstitial tissue includes connective tissue cells and fibers, blood vessels , and Leydig cells which produce testosterone. The most primitive cells lie next to the basement membrane of the seminiferous tubules, and the germ cells move toward the lumen as they mature. Spermatogonia have a small round nucleus and are adjacent to the basement membrane. They divide mitotically, forming more spermatogonia, or they mature into primary spermatocytes.
Primary spermatocytes undergo a final round of DNA synthesis and enter meiosis .
They have a large nucleus that contains distinct meiotic chromosomes . They subsequently divide, forming secondary spermatocytes with a haploid number of chromosomes. Secondary spermatocytes are round cells, smaller than primary spermatocytes. They divide rapidly to form spermatids, so they are infrequently seen in sections. Spermatids do not divide but develop into spermatozoa by the process of spermiogenesis, which has many steps.