Anocutaneous line

Illustration of the anocutaneous line

The anocutaneous line, also known as the Hilton's line, is an important anatomical landmark located in the anal canal. It marks the transition between the anal canal and the perianal skin. This line is significant in distinguishing between the different types of epithelium and the nerve supply in the anal region.

Anatomy

The anocutaneous line is situated approximately 1 to 2 cm above the anal verge. It is the point where the stratified squamous epithelium of the anal canal transitions to the keratinized stratified squamous epithelium of the perianal skin. This transition is crucial for understanding the different types of epithelial tissue present in the anal region.

Clinical Significance

The anocutaneous line is clinically significant because it demarcates the boundary between the internal and external hemorrhoids. Internal hemorrhoids occur above this line and are covered by rectal mucosa, while external hemorrhoids occur below this line and are covered by skin. This distinction is important for the diagnosis and treatment of hemorrhoidal disease.

Additionally, the nerve supply changes at the anocutaneous line. Above the line, the anal canal is innervated by the autonomic nervous system, which means it is insensitive to pain. Below the line, the area is innervated by the somatic nervous system, making it sensitive to pain, touch, and temperature.

Related Structures

• Anal verge
• Pectinate line
• Anal sphincter
• Rectum

Related Pages

• Anal canal
• Hemorrhoids
• Epithelium
• Nervous system