. A laboratory manual and text-book of embryology. Embryology. 2l8 UROGENITAL SYSTEM sexes there also develop a pair of female ducts (of Mueller). In embryos of 10 to n mm. the Muellerian ducts develop as-ventro-lateral thickenings of the uro- genital epithelium at the level of the third thoracic segment and near the cranial ends of the mesonephroi. Next, a ventro-lateral groove appears in the epi- thelium of the mesonephric fold (Fig. 215 A). Caudally, the dorsal and ventral lips of the groove close and form a tube which separates from and lies beneath the epithelium (Fig. 215 B). Cranially,
. A laboratory manual and text-book of embryology. Embryology. 2l8 UROGENITAL SYSTEM sexes there also develop a pair of female ducts (of Mueller). In embryos of 10 to n mm. the Muellerian ducts develop as-ventro-lateral thickenings of the uro- genital epithelium at the level of the third thoracic segment and near the cranial ends of the mesonephroi. Next, a ventro-lateral groove appears in the epi- thelium of the mesonephric fold (Fig. 215 A). Caudally, the dorsal and ventral lips of the groove close and form a tube which separates from and lies beneath the epithelium (Fig. 215 B). Cranially, the tube remains open as the funnel-shaped ostium abdominale of the Muellerian duct. The solid end of the tube grows caudalward beneath the epithelium, lateral to the mesonephric or male ducts Lateral body wall .Jk Muellerian. Mesentery Mesonephric tubule Genital aland Aniacje of Muellerian duct Fig. 215.—Transverse sections through the anlage of the right Muellerian duct from a 10 mm. embryo. A, showing the groove in the urogenital epithelium; B, three sections caudad showing the tubular anlage of the duct. X 250. (Figs. 216 and 218). Eventually, by way of the genital cord, the Muellerian ducts reach the median dorsal wall of the urogenital sinus and open into it. Their further development into uterine tubes, uterus and vagina is described on page 226. Embryos not longer than 12 mm. are thus characterized by the pos- session of indifferent genital glands, and of both male and female genital ducts. There is as yet no sexual differentiation. The development and position of the Muellerian ducts is well shown in ventral dissections of pig embryos (Figs. 216 and 217). Note the enormous size of the mesonephroi. Differentiation of the Testis.—In male embryos of 13 to 15 mm. the genital. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly rese
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectembryology, bookyear1
