An elongated, contractile cell found wrapped about precapillary arterioles outside the basement membrane. Pericytes are present in capillaries where proper adventitia and muscle layer are missing (thus distingushing this cell type from adventitial cells). They are relatively undifferentiated and may become fibroblasts, macrophages, or smooth muscle cells. [ https://www.worldcat.org/search?q=bn%3A0721662544 http://www.ncbi.nlm.nih.gov/pubmed/20024907 http://www.ncbi.nlm.nih.gov/pubmed/17986482 http://id.nlm.nih.gov/mesh/D020286 http://www.ncbi.nlm.nih.gov/pubmed/16807374 ]