The Uterus
The uterus gives a misleading impression of consisting of a relatively long body succeeded by two divergent, tapering horns coiled ventrally on themselves (Fig. 29.15). Actually the apparent body is furnished by the two horns lying within shared serosal and muscular coats, which is an arrangement suggested by a dorsal groove.
The diverging horns are bridged by short dorsal and ventral intercornual ligaments (Fig. 29.14/4). The ligaments create a small pocket that allows placing of a finger to fix the organ during rectal examinations. The tight winding of the horns is not constant but results from stimulation of the muscle of the organ and of the broad ligament; the uterus appears to become more definite and firmer in the course of a rectal examination. The effect is most noticeable during estrus.The firmness of the cervix permits recognition of the caudal limit of the body of the uterus during handling, but there is nothing to indicate its cranial limit. The dissection reveals that the body is a mere 3 cm in length while the cervix measures 8 to 10 cm. Each horn measures 35 cm or so, of which about one third is incorporated in the "pseudobody." The cervix begins at the constriction of the internal uterine ostium, beyond which the passage is occluded by the interlocking of projections from the walls; these consist of three or four circular folds in virgin animals, but these become broken and irregular in multipara. The most caudal fold projects into the vagina, where it is surrounded by an annular fornix. The cervical mucosa also shows longitudinal folds that, on reaching the external ostium, radiate in a fashion recalling the segments of an orange (Fig. 29.16A and B). Many irregular, originally circular folds project into the lumen, fitting closely together; the last one is sunken into a recess of the vaginal wall. In combination, these features make catheterization of the uterus very difficult if not impossible at most stages of the cycle for insemination or embryo transfer.
Most features that distinguish the uterus of the small ruminants are of little practical importance. The most characteristic feature of the interior of the uterus are the caruncles, the attachment sites of the fetal membranes in pregnancy. About 40 of these are arranged in four more or less regular rows in the wider parts of the horn, reducing to a double line toward the tip. The free surfaces of the caruncles are concave, most obviously in the ewe (Fig. 29.17).
Surgical Approach to the Uterus: The uterus can be approached for surgical procedures such as the cesarean section in the standing animal via the flank approach. In this approach the paralumbar fossa is desensitized through caudal epidural anesthesia or paravertebral nerve block.