What are the functions of gastrointestinal smooth muscle

The structure of our body's digestive tract smooth muscle is more complex than that of the stomach smooth muscle. The main motor functions of the digestive tract smooth muscle are contraction and relaxation. The reason why food can continuously move downward in our gastrointestinal tract, in addition to gravity, is that the contraction and relaxation of the smooth muscles of the digestive tract are the main driving force for the movement of food. If there were no smooth muscles of the digestive tract, then we would have no way to complete the process of digesting food. Let's take a look at the characteristics of the smooth muscles of the digestive tract.

The walls of the digestive tract are mainly composed of visceral smooth muscle, except for the upper mouth, pharynx, esophageal end and external anal sphincter, which are striated muscle. The smooth muscles of the digestive tract move synchronously through tight junctions to complete muscle contraction and relaxation to push food forward, complete mechanical digestion of food, and promote chemical digestion and absorption. Although the smooth muscle of the digestive tract has the common characteristics of muscle tissue, such as excitability, conductivity, and contractility, it is not exactly the same as skeletal muscle and cardiac muscle and has its own particularities.

The smooth muscle of the digestive tract can stretch greatly to adapt to actual needs. After eating, it can stretch several times than usual. The stomach is most obvious and can accommodate food several times its original volume. The stretchability of the cardiac muscle and skeletal muscle cannot exceed 50% of its original length. For a hollow container, this property allows it to hold more food without causing noticeable changes in pressure.

The smooth muscles of the digestive tract often maintain a weak and continuous contraction state, which is called smooth muscle tone or tonic contraction. Due to the existence of this tension, a certain basic pressure is always maintained in the digestive tract, and the stomach and intestines maintain a certain position and shape. Various contraction movements of the digestive tract are also carried out on the basis of the tonic contraction of smooth muscles. The tone of smooth muscle is myogenic. After cutting off the external nerves that control the smooth muscle, the tone still exists. However, in general, the tone of the smooth muscle of the digestive tract is regulated to a certain extent by the central nervous system and hormones.

Many friends may feel abdominal bloating or constipation, which is often closely related to abnormalities in our digestive tract smooth muscles. For example, when the contraction function of the digestive tract smooth muscles is abnormal, food will take longer to pass through the gastrointestinal tract, and the water in the food will be more easily absorbed by the gastrointestinal wall, which will cause dryness, and the stool will become dry and hard.