KEY AC, adipose cells BV, blood vessels G, gonocytes LC, Leydig cells MT, mediastinum testis RT, rete testis ST, seminiferous tubules TA, tunica albuginea TR, tubulus rectus
The rete testis, in turn, is connected via 20 efferent ductules (ductuli efferentes; remnants of nephrons of the fetal mesonephric kidney) to the ductus epididymis. These are the first elements of the excurrent duct system of the male genital system. Most of the fluid secreted in the seminiferous tubules is reabsorbed in the efferent ductules. The muscular coat characteristic of the excurrent duct system first appears at the beginning of the efferent ductules. The ductus epididymis is a highly coiled tube, 4 to 6 m long; sperm mature during their passage along its length, acquiring motility as well as the ability to fertilize an egg. This maturation is also androgen dependent and involves changes in the sperm plasma membrane and addition to the glycocalyx of glycoproteins secreted by the epididymal epithelial cells.
Efferent ductules, testis-epididymis, monkey, H&E 60; inset 360.
About 12 to 20 efferent ductules leave the testis and serve as channels from the rete testis to the ductus epididymis. Each of the efferent ductules undergoes numerous spiral windings and convolutions to form a group of conical structures; together they constitute the initial part of the head of the epididymis. When examined in a 822 tissue section, the ductules exhibit a variety of irregular profiles due to their twisting and turning. This is evident on the right side of this micrograph. The epithelium that lines the efferent ductules is distinctive in that groups of tall columnar cells alternate with groups of cuboidal cells, giving the luminal surface an unevenly contoured appearance. Thus, small cup-like depressions are created where the epithelium contains groups of cuboidal or low columnar cells. Typically, these shorter cells exhibit a brush border-like apical surface because of the microvilli that they possess (arrowhead, inset).
PLATE 88 • E FFE R E NT DUCTU LE S AN D E P I DI DYM I S KEY AT, adipose tissue BV, blood vessel C, cilia CT, connective tissue P, pigment SC, stereocilia SM, smooth muscle arrowhead (inset), brush border arrows, “islands” of epithelium in the lumen
Epididymis, monkey, H&E 180.
The epididymis, by virtue of its shape, is divided into a head, body, and tail. The initial part of the head contains the ductus epididymis, a single convoluted duct into which the efferent ductules open. The duct is, at first, highly convoluted but becomes less tortuous in the body and tail. A section through the head of the epididymis, as shown in figure above, cuts the ductus epididymis in numerous places, and as in the efferent ductules, different-shaped profiles are observed.
The epithelium contains two distinguishable cell types: tall columnar cells and basal cells similar to those of the efferent ductules. The epithelium is, thus, also pseudostratified columnar. The columnar cells are tallest in the head of the epididymis and diminish in height as the tail is reached. The free surface of the cell possesses stereocilia (SC). These are extremely long, branching microvilli. They evidently adhere to each other during the preparation of the tissue to form the fine tapering structures that are characteristically seen with the light microscope. The nuclei of the columnar cells are elongated and are located a moderate distance from the base of the cell.