THE UTERUS. 



2003 



Fig. 1697. 



Peritoneum 

 (perimetrium) 

 Cavity of 

 body 



Posterior 

 fornix 



THE UTERUS. 



The uterus, or womb, is a hollow muscular organ, receiving the Fallopian tubes 

 above and opening into the upper part of the vagina below, in which the fertilized 

 ovum is retained and undergoes development, and from which the resulting foetus 

 is expelled at the completion of pregnancy. Its lower segment is embedded within 

 the pelvic floor between the bladder and the rectum, while its upper and larger end 

 is free and movable and rests upon the superior surface of the bladder (Fig. 1700). 

 Before undergoing the profound changes incident to pregnancy, the uterus, pear- 

 shaped in its general form, measures about 7 cm. (2^ in.) in length, of which the 

 lower 2.5 cm. (i in.) constitutes the cylindrical neck or cervix (cervix uteri), and the 

 remainder the body (corpus uteri). Its greatest breadth is about 4 cm. (i^ in.) and 

 its thickness about 2.5 cm. (i in. ). In women who have borne children, the uterus 

 seldom quite returns to its virgin size, but shows a permanent increase of about i cm. 

 in its various dimensions, except in the cervix, which is relatively shorter than before. 

 The convex upper extremity of the organ, above 

 the level of the entrance of the Fallopian tubes, 

 is known as Xheftatdus (fundus uteri), which in 

 front and behind passes into the anterior and 

 posterior surfaces and at the sides into the lat- 

 eral borders (margo laterales). Of the two sur- 

 faces, the anterior (facies vesicalis) is the more 

 flattened and less convex and only partially cov- 

 ered with peritoneum, while the more rounded 

 and projecting posterior surface (facies intesti- 

 nalis) is almost completely invested with perito- 

 neum. The lower end of the cylindrical cervix, 

 flattened somewhat from before backward and 

 slightly tapering downward, is divided by the 

 attachment of the surrounding vaginal wall, 

 which it seemingly pierces, into a free lower seg- 

 ment (portio vaginalis), that projects into the 

 vault of the vagina, and an upper one above the 

 ring of attachment (portio supravaginalis). Be- 

 low, the vaginal segment of the cervix termi- 

 nates in thick, rounded, and prominent lips that 

 bound a sunken opening, the external os (ori- 

 ficium externum uteri) that marks the lower limit 

 of the cervical canal and is directed towards the 

 posterior vaginal wall. Owing to the horizontal position of the cervix, the thicker 

 anterior lip (labium anterius cervicis) is shorter and somewhat lower than the over- 

 hanging /'^.y/^r/<?/' /z)^ (labium posterius cerAicis). 



The weight of the virgin uterus varies between forty and fifty grammes ( i Ys- 

 i^ oz. ), that of the organ after pregnancy being about twenty grammes (.7 oz. ) 

 more. 



The cavity of the uterus is small in comparison with the size of the organ and 

 the thickness of its walls, and differs in form according to the plane of section. In 

 sagittal section, it is little more than a narrow cleft separating the opposed anterior 

 and posterior walls, and measures about 6 cm. (2 3/^ in.), of "which 2.5 cm., (i in.) 

 belongs to the cervix. In frontal section, the cavity of the body is triangular in out- 

 line (Fig. 1698), the apex being below, where the upper end of the cavity of the cer- 

 vix passes into that of the body, and the base above, between the tubal orifices which 

 mark the lateral angles. The sides of the triangle are not straight but convex, owing 

 to the inward curve of the thick projecting uterine walls. The greatest transverse 

 width of the cavity of the body, just below the tubal openings, is about 2.5 cm. 



The canal of the cervix (canalis cervicis uteri), as the lower segment of the uterine 

 cavity is called, is fusiform in longitudinal sections, being widest midway between the 

 external os below and the somewhat smaller and more circular internal os (orificium 

 internum uteri) above, where the contracted lumen of the virgin uterus expands into 



Vagina 



Uterus laid open by sagittal section, showing 

 cavity and relations of labia to vagina. 



