Physiology of Testicular Function

DOI: 10.1007/978-3-540-78355-8_2 In book: Andrology, pp.11-59


The testes produce the male gametes and the male sexual hormones (androgens). The term spermatogenesis describes and includes all the processes involved in the production of gametes, whereas steroidogenesis refers to the enzymatic reactions leading to the production of male steroid hormones. Spermatogenesis and steroido-genesis
take place in two compartments morphologically and functionally distinguishable from each other. These are the tubular compartment,
consisting of the seminiferous tubules (tubuli seminiferi) and the interstitial compartment (interstitium) between the seminiferous tubules (Figs. 2.1 and 2.2). Although anatomically separate, both compartments are closely connected
with each other. For quantitatively and qualitatively normal production of sperm the integrity of both compartments is necessary.
The function of the testis and thereby also the function of its compartments are governed by the hypothalamus and the pituitary
gland (endocrine regulation). These endocrine effects are mediated and modulated at the testicular level by local control mechanisms (paracrine and autocrine factors).

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    • "Type B spermatogonia then give rise to spermatocytes that progress into meiosis to form haploid round spermatids, which transcribe high levels of messenger ribonucleic acids (mRNAs) that are not translated until spermiogenesis (O'Donnell et al., 2006). During spermiogenesis, mature round spermatids transform into spermatozoa, which, in mammals, sequentially includes formation of the acrosome from the Golgi apparatus, elongation of the spermatids, and condensation of the nucleus, which becomes transcriptionally arrested as histones are replaced by protamines (Weinbauer et al., 2010). Elongation of the spermatids continues until the flagellum is fully formed, which is concomitant with extrusion of most of the cell cytoplasm, the so-called residual body, which is phagocytosed by the Sertoli cell (Weinbauer et al., 2010). "
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    ABSTRACT: Fluid homeostasis is recognized as a critical factor during the development, maturation, and function of vertebrate male germ cells. These processes have been associated with the presence of multiple members of the aquaporin superfamily of water and solute channels in different cell types along the reproductive tract as well as in spermatozoa. We present a comparative analysis of the existing knowledge of aquaporin biology in the male reproductive tissues of mammals and teleosts. Current data suggest that in both vertebrate groups, aquaporins may have similar functions during differentiation of spermatozoa in the germinal epithelium, in the concentration and maturation of sperm in the testicular ducts, and in the regulation of osmotically induced volume changes in ejaculated spermatozoa. Recent studies have also provided insight into the possible function of aquaporins beyond water transport, such as in signaling pathways during spermatogenesis or the sensing of cell swelling and mitochondrial peroxide transport in activated sperm. However, an understanding of the specific physiological functions of the various aquaporins during germ cell development and sperm motility, as well as the molecular mechanisms involved, remains elusive. Novel experimental approaches need to be developed to elucidate these processes and to dissect the regulatory intracellular pathways implicated, which will greatly help to uncover the molecular basis of sperm physiology and male fertility in vertebrates. © 2015 Marine Biological Laboratory.
    Biological Bulletin 08/2015; 229(1):93-108. · 1.64 Impact Factor
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    ABSTRACT: Two concepts have been put forward to explain the regulation of testicular function. Firstly, it has been suggested that testicular function is regulated primarily by pituitary gonadotropins (endocrine regulation). Secondly, it has been proposed that the “testis is not a mass of independently developing cells” (Roosen-Runge, 1952), so there are presumably local regulatory mechanisms to coordinate the activities of testicular cells (paracrine regulation). It is now generally accepted that there is no conflict between the concepts of peripheral control of testicular function and intratesticular control. The integration of these two concepts accounts for gonadotrophins regulating testicular paracrine activities and some paracrine factors regulating the testicular effects of pituitary hormone and exerting endocrine control over pituitary function.
    Male Reproductive Function, 01/1970: pages 41-64;
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