350 



HISTOLOGY 



W.d. 



M.d. Wd. 



tion of the genital apparatus shown in Fig. 306, B, p. 311, both being 

 sketched from the beautiful lithographs accompanying Keibel's funda- 

 mental account of the development of the human urogenital tract, which 

 students should consult in its original form (Arch. f. Anat. u. Entw., 1896, 

 pp. 55-156). A fusion of the Miillerian ducts begins just above their 

 lower termination and extends downward to the urogenital sinus. Thus 

 the entire ducts form a Y-shaped structure, and the lower part of the stem 

 becomes the vagina. It is at first a solid cord of cells, but those in the 

 center break down and a lumen appears, "first in embryos of 150-200 

 mm." The lower end of the vagina remains 

 closed by epithelium for some time longer, and as 

 the vagina enlarges, a transverse fold, the hymen, is 

 formed at this point. With the breaking down of 

 the central cells, the hymen becomes perforate; it 

 then usually forms a crescentic fold on the dorsal 

 side of the entrance to the vagina (Fig. 353). Its 

 remains permanently mark the orifice of the Miil- 

 lerian ducts. 



Above the vagina the Mullerian ducts form 

 the lining of the uterus, which develops from the 

 upper part of the stem of the Y, and from the 

 inner ends of its arms. This region of junction 

 becomes surrounded by a very thick layer of 

 smooth muscle. The occasional occurrence of a 

 median septum in the uterus or vagina, dividing 

 them into right and left halves, is due to imperfect fusion of the Mullerian 

 ducts. 



The outer portions of the Mullerian ducts retain relatively thin walls 

 and become the uterine (or Fallopian) tubes. Each opens freely through 

 its fimbriated extremity into the abdominal cavity. 



The Wolffian Bodies and Wolffian Ducts. In the female these struc- 

 tures become functionless and degenerate. Their principal derivative 

 is a group of blind tubules, which may readily be seen in the translucent 

 mesentery-like membrane extending between the ovary and tube. These 

 tubules were named the "organ of Rosenmuller" after their discoverer, 

 who described them in 1802, and were called the "parovarium" (later 

 corrected to paroophoron) because of their position beside the ovary; 

 but when it was shown that these tubules were homologous with the 

 epididymis, they were given a corresponding name, and are now known 

 as the epoophoron ( Vt, upon; <Lo<6pos, ovary). The epoophoron consists 

 of "8 to 20" transverse ducts, which begin with blind ends in or near the 

 upper end of the ovary and follow a more or less convoluted course to the 

 longitudinal duct, into which they empty (Fig. 353). They are lined with 



U.S. -/ - 



FIG. 352. RECONSTRUCTION 

 SHOWING THE FUSION OF 

 THE MULLERIAN DUCTS. 

 (After Keibel.) 



bl., Bladder; M.d., Mulleriae 

 duct; u., ureter; ur., uru- 

 thra; u.s., urogenital 

 sinus; W.d., Wolffian duct. 



