THE UTERUS 601 
The two horns are commonly unsymmetrical in length and diameter in mares which have borne 
young. 
The body of the uterus (Corpus uteri) is situated partly in the abdominal, 
partly in the pelvic, cavity. It is cylindrical, but considerably flattened dorso- 
ventrally, so that in cross-section it is elliptical. Its average length is seven or 
eight inches (ca. 18-20 cm.), and its diameter, when moderately distended, about 
four inches (10 cm.). Its dorsal surface (Facies dorsalis) is related to the rectum 
and other parts of the intestine. Its ventral surface (Facies ventralis) is in contact 
with the bladder, and has inconstant relations with various parts of the intestine. 
The term fundus uteri is applied to the wide anterior part from which the cornua 
diverge. 
The position of the body of the uterus is variable, especially in regard to its anterior part. 
It is often pressed up against the rectum, and may be deflected to either side—most frequently 
to the left—by the pelvic flexure of the great colon or coils of the small colon. 
The neck or cervix of the uterus (Cervix uteri) is the constricted posterior 
part which joins the vagina. It is about two to three inches (5—7.5 cm.) in length, 
and an inch and a half (3.5-4 em.) in diameter. Part of it (Portio vaginalis uteri) 
projects into the cavity of the vagina; it is therefore not visible externally, but 
may be felt through the vaginal wall. 
Attachments.—The body and horns are attached to the abdominal and pelvic 
walls by two extensive peritoneal folds, the broad ligaments of the uterus (Liga- 
menta lata uteri). These extend on either side from the sublumbar region and the 
lateral pelvic walls to the dorsal border of the cornua and the lateral margins of the 
body of the uterus. They contain the vessels and nerves of the uterus and ovaries, 
connective tissue, and a large amount of unstriped muscular fibers which are con- 
tinuous with those of the uterus. The ureters are situated along their parietal 
margins. The lateral layer of each gives off a fold, the round ligament of the uterus 
(Ligamentum teres uteri), which blends with the parietal peritoneum over the 
abdominal inguinal ring; its anterior extremity is situated above the extremity of 
the cornu and forms a long round appendix. It contains muscular tissue, vessels, 
and nerves, and is the homologue of the gubernaculum testis. The anterior part of 
the neck is continuous with the vagina, and thus has a more fixed position than the 
rest of the organ. 
The cavity of the uterus (Cavum uteri) is largely obliterated in the non- 
pregnant state by the contraction of the wall and by folds of the mucous lining. 
At the extremity of each cornu it communicates with the uterine tube by a minute 
opening on a small papilla. The cavity of the neck is termed the cervical canal 
(Canalis cervicis); it is closed ordinarily by mucous folds and a plug of mucus. 
It opens into the vagina by the orificium externum uteri,! and into the body by the 
orificium internum uteri. 
Structure.—The wall of the uterus consists of three coats. The serous coat 
(Perimetrium) is, for the most part, closely adherent to the muscular coat. It is 
continuous with the broad ligaments. The muscular coat consists essentially of 
two layers, a thin external stratum of longitudinal fibers, and a thick internal layer 
of circular fibers. Between these is a very vascular layer (Stratum vasculare) of 
connective tissue with circular and oblique muscular fibers in it. The circular coat 
is very thick in the neck, where it forms a sphincter half an inch or more (ea. 1.5 em.) 
in thickness. The mucous membrane rests directly on the muscular coat, and is 
brownish-red in color, except in the neck, where it is pale. It is covered by asingle 
layer of high columnar cells, and contains numerous long, branched tubular uterine 
glands (Glandule uterine); these are absent in the cervix. 
Vessels and Nerves.—The chief arteries are the uterine and the uterine 
branch of the utero-ovarian, which have a flexuous course in the broad ligaments; 
1 This is frequently designated the os uteri. 
