Length of anal canal: (A) 10 - 15 mm, (B) 15 - 20 mm, (C) 25 - 30 mm, (D) 35 - 40 mm
Answer is D. 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