The presence of muscular tissue in the alimentary canal indicates that some sort of movements must be present in the gastro-intestinal tract. As a matter of fact, the alimentary canal does move, its different parts showing different kinds of movements.
Reason for Movement:
If one recollects the chief functions of the digestive tract, such as digestion, secretion, absorption, defecation etc., it would be evident that, unless some kind of movement is present in the gastrointestinal tract, the latter will not be able to perform its functions properly. For instance, movements are necessary to propel the food mass onwards, in order to bring it in contact with the different digestive juices and also for thorough mixing.
Movements are also necessary to ensure active circulation through the walls of the gut, so that secretion and absorption may proceeds rapidly. Lastly, movements are essential for the process of defecation. All these considerations show that movements are essential requisites for the proper functioning of the digestive tract.
Facts about Movement:
The broad facts about the movements are as follows:
There are many varieties of movements, such as peristalsis, antiperistalsis, mass peristalsis, segmentation, pendular, tonus rhythm, etc.
Functionally, they can be put into two groups:
i. Translatory Movements – These types of movements travel onwards and propel the food mass, viz., peristalsis, antiperistalsis, and mass peristalsis.
ii. Stationary Movements – These movements remain localised and do not move onwards, viz., segmentation, tonic contraction, etc. Translatory movement is present in every part of gastro-intestinal tract but not the stationary movements.
2. Cause of Movements:
i. Peristaltic and antiperistaltic movements are neurogenic, i.e., depending on nerves,
ii. Segmentation or pendulum is myogenic, i.e., depending on muscles only.
3. Relation with Degree of Activity:
Movements are directly related to the degree of activity of the part. Greater the degree of activity greater will be the variety and rate of movements. Small intestine, being the most active part, shows the maximum varieties of movements.
Each type of movement has the following characteristics:
ii. Frequency (i.e., its number per minute)
iii. Rate of propagation (if it is translatory), and
iv. Cause (neurogenic and myogenic)