Spermatozoen

Spermatozoen, also known in English as spermatozoon (singular) and spermatozoa (plural), are the male gametes of animals. They are haploid cells produced by meiosis in the testes and mature through extensive remodeling in the epididymis. Their primary role is to deliver paternal DNA to the female gamete during fertilization.

A mature spermatozoon has three main regions. The head contains the condensed nucleus with the paternal set of chromosomes and an acrosome, a cap-like structure that houses enzymes necessary for penetrating the outer layers of the oocyte. The midpiece is rich in mitochondria, supplying the energy (ATP) required for motion. The tail, or flagellum, provides motility, enabling the cell to swim toward the egg.

Spermatogenesis is the process that generates spermatozoa. It begins with spermatogonial stem cells in the seminiferous tubules and progresses through meiosis to form haploid spermatids, which then undergo spermiogenesis to become elongated, streamlined spermatozoa. After leaving the testes, sperm gain further maturity and functional competence during passage through the epididymis.

In fertilization, spermatozoa often undergo capacitation in the female reproductive tract, which primes them for the acrosome reaction. This reaction releases enzymes that help the sperm penetrate the zona pellucida and fuse with the oocyte membrane, delivering the paternal genome and initiating embryonic development.

Clinical relevance includes assessment of sperm quality for fertility evaluations, focusing on concentration, motility, and morphology. Sperm can be collected by ejaculation or retrieved surgically, and may be stored by cryopreservation for assisted reproductive technologies.