Spermatids and Spermiogenesis

Abstract

The two maturation divisions of each spermatocyte result in four haploid cells, spermatids. These differentiate into spermatozoa, a process called spermiogenesis which ends when the spermatozoa are released from the seminiferous epithelium. After the haploid round spermatids are formed, their nuclear and cytoplasmic components undergo a complex series of morphological, histochemical and biochemical changes ending with the production of highly differentiated and specialized germ-cells, the spermatozoa, which become “free” cells (Fig. 17). The spermatozoon shows a distinct architectural polarity more extensive than any observed in somatic cells. The various alterations of differentiating spermatids occur in the absence of DNA synthesis or cytokinesis and are known to be accompanied by conspicuous changes in plasma membrane components (Chap. V). Actually, mammalian spermatozoa develop many unusual characteristics at the cell surface, which will be discussed in Chap. X.