446 ANATOMY FOR NURSES [Chap. XXI 



in the body, is constricted above, where it opens into the body 

 by means of the internal orifice (internal os), and below, where it 

 opens into the vagina by means of the external orifice (external os). 



Fig. 206. — Internal Organs of Generation. Showing the uterus in its nor- 

 mal position between the bladder and the rectum. (Cooke.) 



Between these two openings the canal of the cervix is somewhat 

 enlarged. 



Structure. — The walls of the uterus are thick and consist of 

 three coats : — 



(1) An external serous coat derived from the peritoneum. It 

 covers all of the uteru.s, and the posterior surface of the cervix, 

 but not the anterior surface. 



(2) A middle muscular coat which forms the bulk of the uterine 

 walls. It consists of layers of plain muscular tissue intermixed 

 with blood-vessels, l\Tnphatics, and nerves. The arrangement of 

 the muscle fibres is very complex, as they run circularly, longi- 

 tudinally, spirally, and cross and interlace in every direction. 



(3) An internal mucous membrane, which is continuous with that 

 lining the vagina and Fallopian tubes. It is highly vascular, pro- 



