Internal Hemorrhoids Location in the Gastrointestinal Tract
Internal hemorrhoids are located in the anal canal, specifically above the dentate line, and are covered by columnar epithelium. 1, 2
Anatomical Definition and Boundaries
The dentate line serves as the critical anatomical landmark that distinguishes internal from external hemorrhoids—internal hemorrhoids originate above this line while external hemorrhoids arise below it. 1, 2
Internal hemorrhoids are vascular cushions positioned in the upper anal canal, which is the terminal portion of the gastrointestinal tract, just above the dentate line and below the rectum. 3
These structures are covered by columnar epithelium (rectal mucosa) rather than the squamous epithelium (anoderm) that covers external hemorrhoids below the dentate line. 1
Structural Composition
Internal hemorrhoids consist of three components: the mucosal lining, the stroma containing blood vessels and smooth muscle with arteriovenous communications, and the anchoring connective tissue system that secures them to the internal sphincter. 4, 5
The anal cushions are normal anatomical structures located at the 3,7, and 11 o'clock positions when viewed in lithotomy position, and they become symptomatic hemorrhoids when abnormally enlarged. 4
These vascular structures contain arteriovenous communications between terminal branches of the superior rectal arteries and rectal veins, which explains the characteristic bright red arterial bleeding seen with internal hemorrhoids. 4
Clinical Significance of Location
The location above the dentate line means internal hemorrhoids are innervated by visceral nerves, which is why they typically present with painless rectal bleeding rather than pain (unless thrombosed or severely prolapsed). 1, 2
Internal hemorrhoids contribute 15-20% of resting anal pressure and play a role in fecal continence and anal canal sensitivity. 3
When the suspensory muscles stretch and these cushions prolapse through the anal canal, they can extend beyond the anal verge, depositing mucus onto the perianal skin and causing secondary irritation. 6
Common Diagnostic Pitfall
- Internal hemorrhoids are typically not palpable on digital rectal examination because they are soft, compressible vascular cushions that collapse under the examining finger—anoscopy with adequate lighting is required for visualization. 6