haustra

Haustra, singular haustrum, are sacculations in the wall of the large intestine that give the colon its characteristic segmented appearance. They are most evident along the colon and are not present in the small intestine or in the rectum. The markings are formed by the wall’s muscular and mucosal architecture and can be seen on radiographic imaging of the colon.

Anatomy and formation: The haustra arise from the action of the taeniae coli, three longitudinal bands of smooth muscle that run along the length of the colon. When these bands contract, they cause puckering of the wall, creating shallow pockets bordered by circular mucosal folds. The resulting haustral pouches extend from the cecum to the rectosigmoid junction, while the rectum generally lacks haustra because it lacks taeniae coli.

Function: Haustration supports segmentation and mixing of colonic contents. By creating discrete pouches, the mucosa has sustained contact with luminal material, which facilitates the absorption of water and electrolytes. The sacculated layout also contributes to a slower transit time, allowing more thorough processing of contents.

Clinical and radiologic relevance: On imaging, haustral markings give the colon its segmented appearance. Loss or attenuation of haustral markings, known as a lead pipe appearance, can be seen in chronic ulcerative colitis and reflects long-standing colonic changes. Haustra aid in distinguishing the colon from the small intestine and help localize pathology within the large bowel.