[Morphological studies of the small intestine in experimental operations to isolate segments from the digestive...

Changes in the small intestine of white rats, developing within fifteen days of experimental operation for the isolation of a segment outside the digestive tract, are investigated using light and fluorescent microscopy. The isolated segment with intact nerve and humoral connections resides in the abdominal cavity. Findings in the distal (functioning) segment reveal hypertrophy of the muscular layers of the small intestine, more intensive development of the loose connective tissue, whereas the villi are shortened and thickened and display a reduced resorptive surface. This occurs at the expense of the considerably augmented number of mucous (calicine) cells, and of the dystrophic and desquamative changes taking place in the resorptive epithelium. In the isolated (lacking function) segment normal blood supply to the submucosa, slight atrophy of the muscle layers, and decreased number of glands of Lieberkühn is observed. In the same time the small intestinal villi are elongated, having larger resorptive surface, and containing reduced number of mucous (calicine) cells, whereas their epithelium is made up of cells with profuse and succulent cytoplasm free of desquamations. The inference is reached that the changes recorded in case of retaining the isolated segment within the abdominal cavity are attributable to the reciprocal action between the two small-intestinal areas by route of the existing neurohumoral linkage. Moreover the processes tend to preserve the isolated segment at the expense of developing structural-functional derangements in the functioning area.