spermatocytogenesis

Spermatocytogenesis is a phase of spermatogenesis in the male reproductive system. It refers to the development by which diploid germ cells in the seminiferous tubules—spermatogonia—proliferate and differentiate into primary spermatocytes, which then enter the meiotic divisions to produce haploid spermatids. In use, the term is sometimes defined narrowly as the mitotic proliferation of spermatogonia to primary spermatocytes, while other sources extend it to include the subsequent meiotic steps leading to spermatids. The exact usage can vary.

Within the seminiferous tubules, spermatogonia divide mitotically to maintain the germ cell line and to form cells destined for meiosis. Spermatogonia are often categorized as type Ad (dark), Ap (pale), and type B; the B-type cells proceed to become primary spermatocytes. Primary spermatocytes then initiate meiosis I, producing secondary spermatocytes, which quickly complete meiosis II to yield haploid spermatids.

Spermatids undergo spermiogenesis, a maturation process in which they are transformed into structurally mature spermatozoa. During this phase, the nucleus condenses, the acrosome forms over the anterior nucleus, mitochondria become organized, and excess cytoplasm is discarded, resulting in streamlined, motile sperm.

Regulation of spermatocytogenesis involves hormonal and paracrine signaling, notably follicle-stimulating hormone and testosterone acting through Sertoli cells to support germ cell development. The process begins at puberty and, in many species, continues throughout adult life, with a spermatogenic cycle occurring along the walls of the seminiferous tubules. Disruptions can contribute to male infertility.