228 UROGENITAL SYSTEM 



fundus, while the narrow cervix of the uterus and the vagina arise from the utero- 

 vaginal anlage. Through the differentiation of its mesenchymatous wall, the 

 uterus is first brought into relation with the round ligament. 



At 50 mm. the mesenchyma begins to differentiate a connective layer tissue. At 80 mm. 

 the mucosa and muscularis may be distinguished. The first circular muscle fibers appear in 

 1 So mm. embryos, the other muscle layers develop later. The epithelium of the uterine tubes 

 and the tubular portion of the uterus (fundus) remains simple with cylindrical or cuboidal 

 cells. The tubular fundus glands of the uterus may not appear until near puberty. At 38 

 mm. the epithelium of the cervix and vagina becomes stratified. The vagina is at first without 

 a lumen. From the third to the sixth months of fetal life dorsal and ventral outgrowths of 

 the epithelium form the fornices of the vagina. The vaginal lumen appears in embryos of 

 150 to 200 mm., arising from the degeneration of the central epithelial cells. The fornices 

 hollow out and form the boundary line between the cervix uteri and the vagina. The epithelial 

 cells of the former become stratified and cylindrical, those of the vagina are of the stratified 

 squamous type. The paired cranial portions of the Muellerian ducts become the uterine tubes. 

 The epithelial anlages of the Muellerian ducts form the epithelial layers of the uterine tubes 

 uterus and vagina. 



The Hymen. — At the point where the utero-vaginal anlage breaks through 

 the wall of the urogenital sinus there is present the tubercle of Mueller, which 

 marks the lower limits of the vagina. The tubercle is compressed into a disk 

 lined internally by the vaginal epithelium, externally by the epithelium of the 

 urogenital sinus. These layers with the mesenchyma between them constitute 

 the hymen, which thus guards the opening into the vagina. A circular aperture 

 in the hymen is for a time closed by a knob of epithelial cells, but later when the 

 hymen becomes funnel-shaped the opening is compressed laterally to form a 

 sagittal slit, the ostium vagina. 



The Growth of the Uterus. — The uterus grows but slowly until near puberty, being about 

 the same length (27 mm.) at birth as in a girl of nine years. Just before and after puberty 

 growth is more rapid, a length of 72 mm. being attained at 18 years. This is nearly the maximal 

 length of the virginal uterus. 



Anomalies. — Owing to the complicated processes leading to their formation, many cases 

 of abnormal uterus and vagina occur. A complete classification of these cases is given by Felix 

 (Keibel and Mall, vol. 2, p. 930). The more common anomalies are (1) complete duplication 

 of the uterus and vagina due to the failure of the Muellerian ducts to fuse; (2) uterus bicornis, 

 due to the incomplete fusion of the ducts. Combined with these defects the lumen of the 

 uterus and vagina may fail, partly or completely, to develop and the vaginal canal may not open 

 to the exterior. (3) The body of the uterus may remain flat (uterus planifundis) or may fail 

 to grow to normal size (uterus fetalis and infantilis). (4) Congenital absence of one or both 

 uterine tubes, uterus, and vagina rarely occurs, but may be associated with hermaphroditism 

 of the external genitalia. 



The Ligaments of the Internal Genitalia. — Female. — The loose mesenchyma 

 of the genital cord gives rise laterally to the broad ligaments of the uterus in 



