Parts
- Caecum: short spiral diverticulum on the right, at the level of the cranial lumbar vertebrae. It communicates only with the colon, through the caecocolic orifice.
- Ascending colon: a short segment running cranially on the right.
- Transverse colon: crosses from right to left, cranial to the root of the mesentery and caudal to the stomach.
- Descending colon: the longest segment; it runs along the left side of the dorsal abdomen, ventral to the sublumbar muscles, to the pelvic inlet.
- Rectum and anal canal: cross the pelvic cavity, ventral to the sacrum, to the anus. The anal sacs open on either side of the anus (4 and 8 o'clock).
Clinical relevance
- Rectal palpation: assesses the prostate, pelvic urethra, sublumbar lymph nodes and pelvic canal.
- Colitis: diarrhoea with mucus, tenesmus and frequent small stools.
- Anal sac disease: impaction, sacculitis and abscesses; anal sac adenocarcinoma can cause hypercalcaemia.
- Perineal hernia: in older intact males the rectum deviates between the muscles of the pelvic diaphragm.
3D model
Schematic shape (illustrative fidelity), placed from landmarks on the skeleton and the scanned organs. It shows topography, not fine morphology.