The development of the human body; a manual of human embryology . n Embryo of 14 MM. al, Allantois; 6, bladder; gt, genital tubercle; i, intestine; n, spinal cord;nc, notochord; r, rectum; sg, urinogenital sinus; ur, ureter; w, Wolf-fian duct.—(Keibel.) umbilicus and is known as the urachus. During the en-largement of the bladder the terminal portions of theurinogenital ducts become taken up into its walls, a pro-cess which continues until finally the ureters and Wolffianducts open into it separately, the ureters opening to thesides of and a little anterior to the ducts. This conditionis reach
The development of the human body; a manual of human embryology . n Embryo of 14 MM. al, Allantois; 6, bladder; gt, genital tubercle; i, intestine; n, spinal cord;nc, notochord; r, rectum; sg, urinogenital sinus; ur, ureter; w, Wolf-fian duct.—(Keibel.) umbilicus and is known as the urachus. During the en-largement of the bladder the terminal portions of theurinogenital ducts become taken up into its walls, a pro-cess which continues until finally the ureters and Wolffianducts open into it separately, the ureters opening to thesides of and a little anterior to the ducts. This conditionis reached in embryos of about 14 mm. (Fig. 206), and in THE URETHRA. 3S50J later stages the interval between the two pairs of ductsis increased (Fig. 207), resulting in the formation of a shortcanal connecting the lower end of the bladder which re-ceives the ureters with the upper end of the urogenitalsinus, into which the Wolffian and Miillerian ducts connecting canal represents the urethra (Fig. 207,ur), or rather the entire urethra of the female and the. Fig. 207.—Reconstruction of the Cloacal Structures op an Em-bryo of 25 MM. bl, Bladder; m, Miillerian duct; r, rectum; sg, urogenital sinus; sy, sym-physis pubis; H, ureter; ur, urethra; w, Wolffian duct.—(Adaptedfrom Keibel.) proximal part of that of the male, since a considerableportion of the latter canal is still undeveloped (see p. 386).From this urethra there is developed, at about the thirdmonth, a series of solid longitudinal folds which projectupon the outer surface and separate from the urethra fromabove downward. These represent the tubules of the 384 THE DEVELOPMENT OF THE HUMAN BODY. prostate gland and are developed in both sexes, althoughthey remain in a somewhat rudimentary condition inthe female. The muscular tissue, so characteristic of thegland in the adult male, is developed from the surroundingmesenchyme at a later stage. The urogenital sinus is in the early stages also tubularin its upper part,
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
