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.

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

Distinction	Above pectinate line	Below pectinate line
Lymph drainage	internal iliac lymph nodes	superficial inguinal lymph nodes (below Hilton's white line)
Epithelium	columnar 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	endoderm	ectoderm
Artery	superior rectal artery	middle and inferior rectal arteries
Vein	superior rectal vein draining into the inferior mesenteric vein and subsequently the hepatic portal system	middle and inferior rectal veins
Hemorrhoids classification	internal hemorrhoids (not painful)	external hemorrhoids (painful)
Nerves	inferior hypogastric plexus	inferior rectal nerves

Additional images

• 

  Microscopic cross section of the anorectal junction.

• 

  Anatomy of the anus and rectum

• Gray1078.png

  Coronal section of rectum and anal canal.

External links

• pelvis at The Anatomy Lesson by Wesley Norman (Georgetown University) (rectum)