Patterns of motility

The colon is an intermittently active organ and three patterns of motility are observed:

(i) segmental contractions which chop and mix the contents, increasing contact with the mucosa where absorption can occur.

(ii) antiperistaltic contractions which propagate toward the ileum. These serve to retard the movement of contents through the colon, allowing additional opportunity for absorption of water and electrolytes to occur. Peristaltic contractions, in addition to influx from the small intestine, facilitate movement of contents through the colon.

(iii) mass movements constitute a type of motility not seen elsewhere in the digestive tube. They are also known also as giant migrating contractions; this pattern of motility resembles a very intense and prolonged peristaltic contraction which strips an area of large intestine clear of contents.

Segmental activity consists of local contractions which are usually effected by circular muscle and lead to the mixing of luminal contents, whereas propulsive activity is largely due to contraction of longitudinal muscle. In the colon, the predominant activity is segmental, with the propulsive type of movement occurring infrequently (3-4 times daily in normals) (Table 7.2).

Table 7.2 Patterns of colonic motility13

Frequency of occurrence

Table 7.2 Patterns of colonic motility13

Frequency of occurrence

Type of movement

At rest

Postprandial

Distance

Rate

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