Spermatids

Spermatids are haploid male germ cells that arise during spermatogenesis as the immediate products of meiosis II of a primary germ cell. They are derived from secondary spermatocytes and are generated within the seminiferous tubules of the testes, in close contact with Sertoli cells, and reside in the adluminal compartment during their differentiation.

Following meiosis II, round spermatids undergo a series of changes known as spermiogenesis. During this process they transform into morphologically mature spermatozoa. Features include nuclear condensation and shaping, development of an apical acrosome formed from Golgi-derived proacrosomal vesicles, assembly of a flagellum for motility, and a marked reduction and remodeling of cytoplasm. The excess cytoplasm is discarded as residual bodies and largely phagocytosed by Sertoli cells. The resulting spermatozoa have a compact, streamlined nucleus, a cap-like acrosome containing enzymes, and a long motile tail.

Genetically, spermatids contain a haploid set of chromosomes (23 in humans), with either an X or a Y sex chromosome, reflecting the outcome of meiosis I/II. Although spermatids themselves do not fertilize oocytes, they are the immediate precursors of haploid sperm. Once fully formed, mature spermatozoa are released into the lumen of the seminiferous tubules and are transported to the epididymis for final maturation and storage.