part of hair follicle outer root sheath hair follicle bulge 2010-10-14T12:21:55Z BTO:0004904 BrendaTissueOBO The bulge is located in the outer root sheath at the insertion point of the arrector pili muscle. It houses several types of stem cells, which supply the entire hair follicle with new cells, and take part in healing the epidermis after a wound. mgr