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(also Rouget cell), a branching cell in the wall of a blood-carrying capillary. The cytoplasm of pericytes is characterized by the presence of fibrillar elements and micropinocytotic vesicles, whose membranes exhibit adenosine triphosphatase activity. The outgrowths of pericytes surround the capillaries and, penetrating the basement membrane, either come into contact with the endothelial cells or are separated from the cells by a narrow space. Some scientists consider pericytes to be partially differentiated cells, capable of being transformed into other cellular elements of connective tissue. Others consider pericytes to be differentiated contractile elements, capable of changing the lumen of the capillary. Still others admit the existence of various types of pericytes, capable of regenerative or contractile functions.