Review: structure and function of the efferent ductules

What is it about?

There have been three major reviews dealing with structure and function of the efferent ductules (Hamilton, 1975; Ilio and Hess, 1994; Robaire and Hermo, 1988). The first two reviews included efferent ductules along with other regions of the epididymis (Hamilton, 1975; Robaire and Hermo, 1988), due to the lack of sufficient information to warrant a separate chapter. Robaire and Hermo (1988) focused on efferent ductules of the rat and gave detailed morphology of the two epithelial cell types, ciliated and nonciliated. They also provided initial discussions of the major function associated with these ductules, namely fluid reabsorption. In 1994, Ilio and Hess, carried these discussions further by including numerous species and showing for the first time morphology of efferent ductules in the dog. Also, from 1988 to 1994, a large number of publications focused on the ultrastructure of these ductules in several species. From 1994 to 2000, there has been a greater focus on the correlation of structure and function, including the major discovery that sulfated glycoprotein-2 (SGP-2), a major secretory protein of Sertoli cells, is synthesized in the same nonciliated cell that is taking up SGP-2 by endocytosis from the ductule lumen (Hermo et al., 1995; Igdoura et al., 1994). A better understanding of efferent ductule physiology has also been uncovered using microcannulation techniques (Clulow et al., 1998). Finally, during this recent period, it was discovered that estrogens play a major role in the regulation of efferent ductule function, and that estrogen receptors are expressed in this region of the male tract to an extent that exceeds even the female reproductive tract (Hess et al., 1997a; Hess et al., 1997b). Based upon these recent studies, there is strong evidence that the efferent ductules are essential for male fertility. There will be an attempt to focus this review on these more recent findings, but important historical data prior to 1994 will also be included to improve our understanding of efferent ductule structure and function.

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Why is it important?

Efferent ductules make up nearly 50% of the head of the epididymis in man and large mammals. Therefore, an understanding of their structure and function is essential for interpreting pathological lesions in the head of the epididymis.