Mechanisms and Classification of Motor Disorders
In pathophysiology, typical disorders of gastric motor function are classified according to the leading mechanism of their occurrence. Three main targets are distinguished, whose damage leads to motility failures: the muscular wall, the sphincter apparatus, and the peristaltic process itself.
Changes in Wall Tone. Normally, the stomach maintains a specific muscle tension. Pathologically, hypertonus (increased tension) or hypotonus (decreased tension) occurs. The extreme degree of hypotonus is atonia—the complete absence of muscle tone. Atonia specifically provokes peristole disorders. The term peristole comes from the Greek words peri (around) and stello (to compress). This is a vital tonic contraction of the musculature that ensures the tight enclosure of the food contained within the stomach.
Sphincter Pathology. Disorders affect the cardiac and pyloric sphincters. Their tone can be excessively decreased or excessively increased. The most severe variant is prolonged spasm. If it occurs in the cardiac region, cardiospasm develops; if in the pyloric region, pylorospasm.
Peristalsis Failures. The movement of the peristaltic wave can be excessively accelerated (hyperkinesia) or, conversely, slowed down (hypokinesia).
Etiology: Why Does Motility Become Impaired?
The causes (etiology) of evacuation function disorders are divided into three large groups: disorders of neural regulation, failures of humoral regulation, and organic pathological processes.
- Disorders of Neural Regulation. The autonomic nervous system directly controls the stomach. Motility increases when the tone of the vagus nerve (n. vagus) is elevated. The suppression of motor function is associated with the activation of the sympathetic nervous system.
- Disorders of Humoral Regulation. Biologically active substances can either stimulate or halt contractions.
- Inhibition of motility is caused by: a high concentration of hydrochloric acid (HCl) in the stomach, as well as an excess of secretin and cholecystokinin.
- Stimulation of motility is observed with a reduced HCl content, as well as against the background of an excess of gastrin and motilin.
- Organic Changes. Structural defects of the stomach—erosions, ulcers, scars, or tumors—inevitably alter contractility. Depending on the localization and severity of the process, they can either weaken or enhance motility.
Pathogenesis and Consequences: Evacuation Disorders
Whatever the primary mechanism may be (wall tone failure, sphincter spasm, or peristalsis disruption), they all share a common outcome. The pathogenesis of the disorders is based on combined or separate disturbances of gastric wall tone and peristalsis, which ultimately leads to impaired evacuation function.
There are two types of disorders of chyme (food mass) evacuation from the stomach into the duodenum:
- Accelerated evacuation.
- Delayed evacuation.
Clinical Manifestations. One of the most frequent manifestations of evacuation disorders is a feeling of heaviness and fullness in the stomach, which occurs even after consuming a small amount of food. This clinical syndrome is underpinned by a specific mechanism: a decrease in the tone and motility of the antral region of the stomach.