Testicular and Epididymal Maturation of Mammalian Spermatozoa
Mammalian spermatozoa are highly differentiated haploid cells which are unable to synthesize proteins de novo post-testicularly. These unique cells undergo morphological and biochemical changes in components as diverse as the plasma membrane, cytoplasm (the cytoplasmic droplet) and certain internal components such as the nucleus, the acrosome, and the cytoskeletal elements (perinuclear theca, outer dense fibers and fibrous sheath). Most of these components are primarily organized into developing germ cells and nascent spermatozoa during spermatogenesis, and the initial maturational modifications occur in the testis, which is typically referred to as testicular maturation. Spermatozoa that have left the testis undergo further modifications in the epididymis referred to as epididymal maturation (1, 2). These changes are commensurate with the physiological and functional events continuously induced in developing spermatids and maturing spermatozoa. Thus, spermatozoa present in the testis and proximal epididymis are immotile and immature (infertile), while spermatozoa that reach the distal epididymis are motile and mature (fertile). In this context, the maturation of spermatozoa is defined as the process of achieving the fertilizing ability.
KeywordsAcrosome Reaction Sperm Maturation Mammalian Spermatozoon Fibrous Sheath Sperm Plasma Membrane
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