Haustrum (anatomy)

In anatomy, a haustrum (plural: haustra) refers to one of the pouches or sacculations in the wall of the colon. Haustra are formed by the teniae coli, which are three distinct longitudinal bands of smooth muscle that run along the outside of the large intestine. Because the teniae coli are shorter than the length of the colon itself, they create a gathering effect, causing the colonic wall to bulge outward between the teniae. These bulges are the haustra.

Haustra are responsible for the characteristic segmented appearance of the colon. Their presence allows for slow, churning movements called haustral contractions, which help to mix the colonic contents (chyme) and promote the absorption of water and electrolytes. The contractions occur as the circular muscle of the colon contracts, squeezing the bolus and moving it slowly from one haustrum to the next. This process increases contact between the chyme and the colonic mucosa, facilitating absorption. The haustra also help to compact the feces.