Length of anal canal
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
10 - 15 mm
15 - 20 mm
25 - 30 mm
35 - 40 mm
Abdomen and pelvis