What structure separates internal and external hemorrhoids?

What structure separates internal and external hemorrhoids?

• A. Anal verge
• B. Pectinate line
• C. Inter-sphincteric line
• D. Perianal skin boundary

Answer: (B)

The boundary between internal and external hemorrhoids is the pectinate (dentate) line in the anal canal. This line marks a transition from endoderm-derived, columnar mucosa above to ectoderm-derived, nonkeratinized stratified squamous epithelium below. It also separates different innervation, blood supply, and lymphatics, which explains why internal hemorrhoids (above the line) are typically not painful and drain through the superior rectal vessels with visceral autonomic innervation, while external hemorrhoids (below the line) are painful due to somatic pudendal innervation via the inferior rectal nerves and drain via the inferior rectal veins.

The boundary between internal and external hemorrhoids is the pectinate (dentate) line in the anal canal. This line marks a transition from endoderm-derived, columnar mucosa above to ectoderm-derived, nonkeratinized stratified squamous epithelium below. It also separates different innervation, blood supply, and lymphatics, which explains why internal hemorrhoids (above the line) are typically not painful and drain through the superior rectal vessels with visceral autonomic innervation, while external hemorrhoids (below the line) are painful due to somatic pudendal innervation via the inferior rectal nerves and drain via the inferior rectal veins.