Abstract
Throughout spermatogenesis multiplication, maturation and differentiation of germ cells results in the formation of the male gamete. The understanding of spermatogenesis needs detailed informations about the organization of the germinal epithelium, the structure and function of different types of germ cells, endocrine and paracrine cells and mechanisms, intratesticular and extratesticular regulation of spermatogenesis. Normal germ cells must be discriminated from malformed, apoptotic and degenerating germ cells and tumor cells.Identification of the border line between normal and disturbed spermatogenesis substantiate the diagnosis of impaired male fertility. The profound knowledge of the complicate process of spermatogenesis and all cells or cell systems involved with is the prerequisite to develop concepts for therapy of male infertility or to handle germ cells in the management of assisted reproduction.
Highlights
Identification of the border line between normal and disturbed spermatogenesis substantiate the diagnosis of impaired male fertility
Starting from a self-renewing stem cell pool, male germ cells develop in the seminiferous tubules of the testes throughout life from puberty to old age
The standard evaluation of the ejaculate does not provide in many cases sufficient information about the defects of spermatogenesis
Summary
Starting from a self-renewing stem cell pool, male germ cells develop in the seminiferous tubules of the testes throughout life from puberty to old age. In comparison to laboratory animals the spermatogenetic efficiency in man appears to be poor In this respect one value of interest is the mean elongate spermatid-Sertoli http://www.rbej.com/content/1/1/107 cell ratio being 3–4 for the human germinal epithelium [26], versus 12 in rats. Even under these conditions the daily rate of spermatozoa production in man is calculated as 3–4 millions per gram of testicular tissue. Intrinsic regulation The Leydig cells in the intertubular space secrete testosterone and additional neuroendocrine substances and growth factors These hormones, transmitters and growth factors are directed to neighbouring Leydig cells, to blood vessels, to the lamina propria of the seminiferous tubules and to Sertoli cells (Fig. 8). Results of histological evaluation of testicular tissue are given in a score count: Score count for the evaluation of spermatogenesis (modified from Ref. [32])
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