Pectinate line

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.)
Details
Identifiers
Latin	Linea pectinata, linea anocutanea
TA	A05.7.05.009
FMA	29321
	Anatomical terminology

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 [1]	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[2]	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
Coronal section of rectum and anal canal.

References

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.
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.

External links

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

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[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.