Large Intestines of the Horse
B. Transverse Colon:
The transverse colon is the short part of the colon that connects the right dorsal colon to the descending colon. It passes from right to left cranial to the cranial mesenteric artery.
C. Descending (Small) Colon:
The descending colon (small) colon is the continuation of the transverse colon, which begins to the left of the root of the mesentery. It has small diameter than the ascending colon, hence it is also known as the small colon. The descending colon is sacculated and has two distinct teniae or bands, namely, the mesenteric and antimesenteric bands. The mesenteric (mesocolic) band is concealed in the attachment of the descending mesocolon. The descending colon together with the loops of the jejunum lie in the left dorsal part of the abdominal cavity. The small colon of the horse is unusually long, when compared to the descending colon of other domestic species. The muscular bands and sacculations of the descending colon can be easily distinguished during rectal palpation.
The rectum continues the descending colon into the pelvic cavity and ends at the short anal canal. The first part is suspended by the mesorectum, but the second part is attached to the surrounding structures by connective tissue and muscular bands. The second part starts at the level of the fourth or fifth sacral vertebra. It is gradually increase in diameter to form a flask-shaped dilatation called the ampulla recti, which extends to the level of the second or third caudal vertebra.