Pectinate Line

Pectinate Line

The pectinate line, also known as the dentate line, anorectal line, or anocutaneous line, is a serrated line that separates the upper two-thirds (or one half) of the anal canal from the lower one-third (or one-half).

In other words, it is the line between the columnar epithelium of the rectum and the stratified squamous epithelium of the anal canal.

Anal canal anatomy
Anal canal anatomy

The epithelium of the distal anal canal can also be divided into two parts. The area above the anocutaneous line is lined with non-keratinized stratified squamous epithelium, while the area below is lined with keratinized stratified squamous epithelium.

The pectinate line also forms the base of the anal columns, which are also referred to as anal valves.

The pectinate line is also the embryological junction between the hindgut and proctodeum.

The dentate line is an important anatomical boundary, and there are many differences above and below the line.

Distinctions Above and Below the Pectinate Line

Distinction Above the Pectinate Line Below the Pectinate Line
Lymphatic drainage Internal iliac lymph nodes Superficial inguinal lymph nodes
Epithelium Columnar epithelium Stratified squamous epithelium
Embryological origin Endoderm Ectoderm
Artery Superior rectal artery < inferior mesenteric artery Middle and inferior rectal (hemorrhoidal) arteries < internal iliac artery
Vein Superior rectal vein > inferior mesenteric vein > portal system Middle and inferior rectal veins > internal iliac vein > systemic circulation
Hemorrhoids Internal hemorrhoids (painless) External hemorrhoids (painful)
Nerves Inferior hypogastric (pelvic) plexus Inferior rectal nerves
dentate line, linea dentata, anorectal line, anocutaneous line
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