pericyte

[pĕrĭ-sīt′]
n.
  1. A slender, relatively undifferentiated, connective tissue cell that occurs about capillaries or other small blood vessels.adventitial cell
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.