<prompt> Diameter of odontoblastic tubules at the point of origin, at their pulpal end3-4 micrometer1 micrometer2-3 micrometer6 micrometer  <response>: Between the odontoblastic processes and the peritubular dentin is the periodontoblastic space which contains the dentinal fluid. The tubules are broader at their point of origin, i.e., at their pulpal end 34μm and become gradually narrower at their point of termination 1μm, i.e., at dentinoenamel or cementoenamel junction. Also the tubules are closer together at the pulpal end 5090,000 tubulesmm2 and further apart at their terminal end. 