Pectinate line

The pectinate line (dentate line) is a line which divides the upper two thirds and lower third of the anal canal. Developmentally, this line represents the hindgut-proctodeum junction.

Pectinate line
Pectinate line labeled at bottom center.
The interior of the anal cami and lower part of the rectum, showing the columns of Morgagni and the anal valves between their lower ends. (Pectinate line visible but not labeled.)
LatinLinea pectinata, linea anocutanea
Anatomical terminology

It is an important anatomical landmark, and several distinctions can be made based upon the location of a structure relative to this line:

DistinctionAbove pectinate lineBelow pectinate line
Lymph drainageinternal iliac [1]superficial inguinal lymph nodes (below Hilton's white line)
Epitheliumcolumnar epithelium (as is most of the digestive tract - the line represents the end of the part of the body derived from the hindgut)stratified squamous epithelium, non-keratinized (until Hilton's white line, where the anal verge becomes continuous with the perianal skin containing keratinized epithelium.)
Embryological origin[2]endodermectoderm
Arterysuperior rectal arterymiddle and inferior rectal arteries
Veinsuperior rectal vein draining into the inferior mesenteric vein and subsequently the hepatic portal systemmiddle and inferior rectal veins
Hemorrhoids classificationinternal hemorrhoids (not painful)external hemorrhoids (painful)
Nervesinferior hypogastric plexusinferior rectal nerves

Additional images


  1. MD, Tao Le, MD, MHS, Vikas Bhushan, MD, Matthew Sochat, MD (2017). First aid for the USMLE step 1 2017 : a student-to-student guide. ISBN 978-0071831420.
  2. Schoenwolf, Gary C.; Bleyl, Steven B.; Brauer, Philip R.; Francis-West, Philippa H. (2014-12-01). Larsen's Human Embryology. Elsevier Health Sciences. p. 372. ISBN 9781455727919.
  • pelvis at The Anatomy Lesson by Wesley Norman (Georgetown University) (rectum)
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