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Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testicle. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. [ 1 ]
The stem cells involved are called spermatogonia and are a specific type of stem cell known as gametogonia. Three functionally separate spermatogonia cell types are recognized on the basis of the appearance of the nuclei : type A dark spermatogonia (Ad), type A pale spermatogonia (Ap), and type B spermatogonia (B).
Spermiogenesis is the final stage of spermatogenesis, during which the spermatids develop into mature spermatozoa. At the beginning of the stage, the spermatid is a more or less circular cell containing a nucleus , Golgi apparatus , centriole and mitochondria ; by the end of the process, it has radically transformed into an elongated ...
The spermatogenesis process in mammals as a whole, involving cellular transformation, mitosis, and meiosis, has been well studied and documented from the 1950s to 1980s. However, during the 1990s and 2000s researchers have focused around increasing understanding of the regulation of spermatogenesis via genes, proteins, and signaling pathways ...
Spermatogonial stem cells are the precursors to spermatozoa, which are produced through a series of differentiation steps. [4] This is the alternative SSC outcome to self-renewal. SSCs survive within microenvironments, termed niches, which provide extrinsic stimuli that drive stem cell differentiation or self-renewal. [24]
The first phases involves the fetal and neonatal phases of germ cell development that lead to the formation of the SSCs. The second phase is spermatogenesis, which is a cycle of regulated mitosis, meiosis and differentiation (via spermiogenesis) leading to the production of mature spermatozoa, also known as sperm cells. [4] [14] [15]
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Capacitation is the penultimate [1] step in the maturation of mammalian spermatozoa and is required to render them competent to fertilize an oocyte. [2] This step is a biochemical event; the sperm move normally and look mature prior to capacitation.