Propulsive peristalsis is the smooth muscle that transports food from the esophagus to the rectum. The undulating and locally synchronized contractions are subject to modulation by the sympathetic and parasympathetic nervous systems. Muscle intrinsic reflexes also play a role in propulsive peristalsis.
What is propulsive peristalsis?
Propulsive peristalsis is the smooth muscle that transports food from the esophagus to the rectum. A specific type of muscle movement is present in the hollow organs of the human body, which is controlled by the autonomic nervous system. This muscle movement is also called peristalsis. It corresponds to a locally synchronized contraction of smooth muscle cells. The undulating phases of contraction and relaxation are reminiscent of the movement of earthworms, for example, and involve the longitudinal and ring muscles. Hollow organs with such a pattern of movement include the esophagus, ureter, fallopian tube, and uterus, as well as the stomach and intestine. The gastrointestinal tract engages in both non-propulsive and propulsive peristalsis in addition to orthograde peristalsis for transport and retrograde peristalsis to reverse the direction of transport. The latter is used for the onward transport of hollow organ contents and depends on the enteric nervous system, which consists of autonomous cellular plexuses in the intestinal and gastric walls and undergoes modulation by the autonomic nervous system. Thus, propulsive peristalsis is a contractile movement that occurs unconsciously and, in the human organism, involves exclusively the segment between the esophagus and the colon. Nonpropulsive peristalsis is not used for onward transport but for mixing the contents of the hollow organ and is present exclusively in the intestine.
Function and task
The intestine is lined with smooth muscle in the intestinal walls. The same is true for the esophagus or stomach. Smooth muscle is carried by all internal organs in vertebrates. The muscle tissue is arranged in layers of different strokes. It consists of 20 to 500 μm large, mononuclear single cells that branch in a spindle shape and are rich in plasma. The functional order is thought to consist primarily of actin filaments and myosin filaments. The actin filaments are loosely anchored in the cell membrane as loose bundles. At their free ends, they are cross-linked by auxiliary proteins, such as desmin. Their contraction is triggered by Ca2+ ions flowing into their cytoplasm. Subsequent phosphorylation in the myosin head is achieved by myosin kinase. The degree of smooth muscle cell shortening is extremely high. Fatigability is conceivably low. In theory, the smooth muscle layers can be controlled directly by the autonomic nervous system. However, the muscle cells are not innervated, but receive excitation signals hormonally. The propulsive peristalsis of these muscles transports food toward the rectum, contributing to the elimination of indigestible, unusable, and utilized food components. Muscle contraction corresponds to a ring-shaped contraction of smooth muscle. The contraction continues continuously and wave-like in one direction. Contraction phases alternate locally synchronized with relaxation phases. Both the intrinsic rhythm of the musculature and locally propagating reflexes contribute to the movement. These reflexes are local muscle intrinsic reflexes that are subject to monosynaptic circuitry and thus have their efferent and afferent pathways in the same organ. The parasympathetic nervous system contributes stimulatory to the modulation of propulsive peristalsis. Its antagonist, the sympathetic nervous system, exerts an inhibitory influence. The parasympathetic and sympathetic nervous systems belong to the autonomic nervous system, which, in addition to the internal organs, primarily modulates the blood circulation. It is thus responsible for controlling all vital functions. Through the two counterparts, the sympathetic and parasympathetic nervous systems, propulsive peristalsis and, with it, the organ activity of the stomach, intestines, and esophagus are controlled extremely finely.
Diseases and disorders
Especially the propulsive peristalsis of the intestine is often affected by complaints. For example, in the context of paralytic ileus, which corresponds to a form of intestinal obstruction. In this disease, the propulsive and non-propulsive peristalsis of the intestine comes to a standstill due to a functional disorder. This ultimately results in intestinal paralysis.Because of the interrupted intestinal passage, food and feces accumulate in the intestine. Paralytic ileus is most often caused by inflammation in the abdominal cavity. In addition to appendicitis, the phenomenon can also be triggered by inflammation of the gall bladder or pancreas. Other conceivable causes are vascular occlusions and various medications. Medication triggers are most commonly opiates and antidepressants. On the other hand, the propulsive peristalsis of the intestine can also cause discomfort due to increases. This is the case, for example, in mechanical ileus. In this phenomenon, intestinal passage is disrupted by a mechanical obstruction. In addition to foreign bodies, fecal pads, and gallstones, intestinal obstructions and intestinal tangles can be considered as mechanical obstacles in the intestinal passage. Peristalsis is exaggerated in the phenomenon, especially in the intestinal segment in front of the obstruction. An extreme case of mechanical ileus is present in the so-called intestinal obstruction, which, in addition to vomiting, is characterized by a bacterial imbalance and resulting inflammatory processes in the intestine. Irritable bowel syndrome also disturbs intestinal peristalsis. This chronic dysfunction can be accompanied by diarrhea and constipation, stomach pain, a feeling of fullness, or a bloated abdomen. The condition of those affected worsens with stress. Therefore, irritable bowel syndrome is categorized as a psychosomatic disorder. The propulsive peristalsis of the esophagus or stomach can also be subject to disorders, for example in the context of injuries or paralysis of the muscles located there. However, these phenomena are far less common than impaired intestinal peristalsis.
