Large Intestines of the Cat
1. Cecum:
The cecum is very small, short comma-shaped diverticulum, located to the right on the median plane. It is related dorsally to the right kidney, ventrally to the ileum and jejunum, and laterally to the descending duodenum and the right lobe of the pancreas. The cecum is connected to the ascending colon at the cecocolic orifice.
2. Colon:
The colon is divided into a short ascending colon, transverse colon, and descending colon. The ascending colon begins at the cecum on the right of the root of the mesentery. It courses cranially for a short distance to join the transverse colon at the right colic flexure. The transverse colon courses from right to left cranial to the root of the mesentery. It joins the descending colon at the left colic flexure. The descending colon extends to the pelvic inlet where it is continued by the rectum.
3. Rectum:
The rectum is short in carnivores. It begins at the pelvic inlet as a continuation of the descending colon. It is attached to the sacrum by the mesorectum. In the male, ventral to the rectum is the urinary bladder, the deferent ducts, the pelvic urethra and the prostate gland. In the female the rectum is related ventrally to the cervix of the uterus and the vagina.
4. Anal Canal:
The anal canal is the very short terminal part of the large intestine, and it continues the rectum to the anus. The mucous membrane of the anal canal is divided into three zones: from cranial to caudal, the columnar zone, intermediate zone, and the cutaneous zone. The columnar zone is indistinct in the cat. The anocutaneous line, or the intermediate zone separates the columnar zone from the cutaneous zone. The cutaneous zone is covered with cornified stratified squamous epithelium and fine hairs, and contains the microscopic circumanal glands. On each side of the cutaneous zone open the ducts of the anal sacs (paranal sinus), which are small reservoir for the secretions of the sebaceous glands that are found in the wall of the sacs. The anal sacs are located ventrolateral to the anus, between the internal and external anal sphincters. The secretion of the anal sacs serves as a marker of identification.