The influence of rhythmic and tonic contraction of the small intestine on blood flow through the intestinal segment.

Abstract

The effects of tonic and rhythmic contraction of the intestine on the arterial and venous blood flow through the intestinal segment were investigated in dogs.Intestinal contractions always caused periodicity in the arterial and venous blood flow. The correlation between intestinal contraction and the arterial and venous flow was classified into three patterns; the contraction phase type, relaxation phase type and combination type were observed in tonic contraction, and the contraction phase type and relaxation phase type in rhythmic contraction.In the contraction phase type, augmentation of venous flow and diminution of arterial flow was elicited during the contraction period. In the relaxation phase type, diminution of venous and arterial flow during the contraction period was followed by sustained augmentation of flow during the relaxation period. The combination of these two patterns is the combination type.Augmentation of venous outflow during the contraction period was produced by expelling blood from the intestinal wall, as the arterial inflow was diminished during this period. Augmentation of arterial and venous flow during the relaxation period was caused by vasodilatation due to prolonged compression of the blood vessel by contraction of the intestinal musculature.