Current aspects of intestinal motility and transport.

The fact that interactions exist between intestinal motility and epithelial transport ist intuitively obvious but difficult to define experimentally. Direction, velocity and rate of flow of intestinal contents depend on the absolute and relative frequency and on the force of stationary and propagated lumen-obliterating (ring) contractions. The motility pattern differs between the fasting and the postprandial state and so do the magnitude and patterns of flow. The fed pattern of motility is primarily modulated by the chemical composition of ingested meals. Changes in epithelial transport are associated with changes in motility and vice versa; these changes are initiated by physical forces or by neuroendocrine reflex activation. Stomach, small intestine and colon are coordinated by antegrade stimulatory and retrograde inhibitory mechanisms which secure completeness of nutrient absorption and facilitate elimination of food residues. Motility and epithelial transport are controlled by intramural and central neural stimulation and by hormones acting systemically, locally (paracrine action), or as neuromodulators.