<prompt> Length of anal canal10 - 15 mm15 - 20 mm25 - 30 mm35 - 40 mm  <response>: The length of the anal canal is about 4 cm range, 3-5 cm, with two thirds of this being above the pectinate line also known as the dentate line and one third below the pectinate line ref - BDC 6e vol2 pg413 