. Cunningham's Text-book of anatomy. Anatomy. DEVELOPMENT OE THE UKINO-GENITAL OBGANS. 1329 fusing posteriorly, give rise to the scrotum in the male. In the female the slit-like opening of the urino-genital canal retains its position, and its margins becoming elongated, form the labia minora. The vaginal opening arises, as we have seen, by a downgrowth of the fused Miillerian ducts which lies in front of the rectum and behind the primitive urino-genital canal. The latter becomes the urethra in the female. In the male the slit- like opening of the urino-genital canal is prolonged anteriorly by
. Cunningham's Text-book of anatomy. Anatomy. DEVELOPMENT OE THE UKINO-GENITAL OBGANS. 1329 fusing posteriorly, give rise to the scrotum in the male. In the female the slit-like opening of the urino-genital canal retains its position, and its margins becoming elongated, form the labia minora. The vaginal opening arises, as we have seen, by a downgrowth of the fused Miillerian ducts which lies in front of the rectum and behind the primitive urino-genital canal. The latter becomes the urethra in the female. In the male the slit- like opening of the urino-genital canal is prolonged anteriorly by an active growth at the base of the genital eminence, and its margins uniting, give rise to the penile portion of the urethra. Neural tube sotochord Muscle plate Mesentery. Umbilical vein Alimentary canal Body cavity The Wolffian Duct and Embryonic Secretory Organ. The Wolffian Duct.—The "Wolffian duct arises in the mesoblast, about the fifteenth day, as a solid cord of cells occupying a position immediately to the lateral side of the protovertebral somites and to the medial side of the body cavity (Fig. 1038). When first recognised the duct lies immediately beneath the epiblast, and as it grows backwards to reach the cloaca it is often found to be intimately con- nected with the epiblast. This close connexion of the duct with the epiblast, in the early stages, is by some authorities supposed to in- dicate a primitive epiblastic origin of the canal, but by others, and apparently with more reason, to be a trace of the opening of ducts on the surface of the body, such as exists in connexion with the excretory organs of lower animals. During the third week the cellular cord which represents the Wolffian duct acquires a lumen, and about the end of the same week the duct in its growth reaches the cloaca. As soon as the cloaca has become divided into dorsal and ventral subdivisions, the Wrolffian duct is seen to end in the caudal part of the ventral subdivision, which becomes
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectanatomy, bookyear1914
