Each seminal vesicle consists of a single tube, coiled upon itself, and giving off several irregular cecal diverticula; the separate coils, as well as the diverticula, are connected together by fibrous tissue. When uncoiled, the tube is about the diameter of a quill, and varies in length from 10 to 15 cm.; it ends posteriorly in a cul-de-sac; its anterior extremity becomes constricted into a narrow straight duct called the excretory duct of seminal gland (or duct of the seminal vesicle), which joins with the corresponding ductus deferens to form the ejaculatory duct[WP]. [ http://en.wikipedia.org/wiki/Excretory_duct_of_seminal_gland ]