<prompt> Zone of HOHL refers to:Cell-free zone.Cell rich zone.Pulp proper.None.  <response>: 1. Cell-free zone Zone of weilWidth approx. 40 μmNot always presentAbsent in young pulp Active secretion of primary dentine and older pulp tertiary dentineCONTENTSCapillariesUnmyelinated nerve fibersCytoplasmic process of fibroblasts2. Cell Rich Zone Zone of HOHLMost numerous cells are fibroblastsFibroblasts secrete Type I and Type III collagenAlso contains undifferentiated mesenchymal stem cells.Vascular supply is extensive and more than cell free zone and odontoblast zone. 