Morphological appraisal of gametogenesis. Spermatogenetic process in mammals with particular reference to man.

The process of spermatogenesis in man can be subdivided into prenatal, postnatal and adult phases. Special attention is devoted to the cytomorphology of the germ cells in these phases, with a more detailed description of the proliferation, maturation and differentiation of the germ cells in the adult. Thus, spermatogonial renewal, meiotic division and the morphological transformations of the spermatids into mature spermatozoa are described. An outline of the structures characteristic of the latter is also given. The histological organization of the seminiferous epithelium is considered, whereby the concepts of the cycle, stage of the cycle and wave of the seminiferous epithelium are discussed. The duration of both the cycle and that of spermatogenesis of the adult are considered. The present review on mammalian, and chiefly human spermatogenic processes aims at: surveying of current concepts, and compiling of the more important facts and problems of spermatogenesis. The nomenclature and definitions advanced here arise from the concept of continuity of the processes of spermatogenesis from embryo to adult.