UTERUS. 751 



Structure. The uterus is composed of three coats : an external serous coat, a 

 middle or muscular layer, and an internal mucous coat. 



The serous coat is derived from the peritoneum ; it invests the fundus and the 

 whole of the posterior surface of the body of the uterus ; but only the upper 

 three-fourths of its anterior surface. 



The muscular coat forms the chief bulk of the substance of the uterus. In the 

 unimpregnated state, it is dense, firm, of a grayish color, and cuts almost like 

 cartilage. It is thick opposite the middle of the body and fundus, and thin at 

 the orifices of the Fallopian tubes. It consists of bundles of unstriped muscular 

 fibres, disposed in layers, intermixed with areolar tissue, blood, and lymphatic 

 vessels and nerves. In the impregnated state, the muscular tissue becomes more 

 prominently developed, and is disposed in three layers ; external, middle, and 

 internal. 



The external layer is placed beneath the peritoneum, disposed as a thin plane 011 

 the anterior and posterior surfaces. It consists of fibres, which pass transversely 

 across 'the fundus, and, converging at each superior angle of the uterus, are con- 

 tinued on the Fallopian tubes, the round ligament, and ligament of the ovary ; 

 some passing at each side into the broad ligament, and others running backwards 

 from the cervix into the recto-uterine ligaments. 



The middle layer of fibres presents no regularity in its arrangement, being 

 disposed longitudinally, obliquely, and transversely. 



The internal or deep layer consists of circular fibres arranged in the form of 

 two hollow cones, the apices of which surround the orifices of the Fallopian tubes, 

 their bases intermingling with one another on the middle of the body of the uterus. 

 At the cervix, these fibres are disposed transversely. 



The mucous membrane is thin, smooth, and closely adherent to the subjacent 

 tissue. It is continuous, through the fimbriated extremity of the Fallopian tubes, 

 with the peritoneum ; and, through the os uteri, with the mucous lining of the 

 vagina. 



In the body of the uterus, it is smooth, soft, of a reddish color, lined by 

 columnar-ciliated epithelium, and presents, when viewed with a lens, the orifices 

 of numerous tubular follicles arranged perpendicularly to the surface. They are 

 of small size in the unimpregnated uterus, but shortly after impregnation they are 

 enlarged, elongated, presenting a contorted or waved appearance towards their 

 closed extremities which occasionally dilate into two or three sacculated extremities. 

 The circular orifices of these glands may be seen on the inner surface of the 

 mucous membrane, many of which during the early period of pregnancy are 

 surrounded by a whitish ring formed of epithelium which lines the follicles. 



In the cervix, the mucous membrane between the rugas and around the os uteri 

 is provided with numerous mucous follicles and glands. The small, transparent, 

 vesicular elevations, so often found within the os and cervix uteri, are due to 

 closure of the mouths of these follicles, and their distension with their proper 

 secretion. They were called the ovula of Naboth. The mucous membrane 

 covering the lower half of the cervix presents numerous papilla?. 



Vessels and Nerves. The arteries of the uterus are the uterine, from the 

 internal iliac, and the ovarian, from the aorta. They are remarkable for their 

 tortuous course in the substance of the organ, and for their frequent anastomoses. 

 The veins are of large size, and correspond with the arteries. In the impregnated 

 uterus, these vessels are termed the uterine sinuses, consisting of the lining mem- 

 brane of the veins adhering to the walls of canals channelled through the substance 

 of the uterus. They terminate in the uterine plexuses. The lymphctics are of 

 large size in the impregnated uterus, and terminate in the pelvic and lumbar 

 glands. The nerves are derived from the inferior hypogastric and spermatic 

 plexuses, and from the third and fourth sacral nerves. 



The form, size, and situation of the uterus, vary at different periods of life, and under different 

 circumstances. 



