Hemorrhoids are known to have afflicted mankind for centuries, yet their pathogenesis remains obscure. Histologically, hemorrhoids do not differ significantly from normal anorectal submucosa; they resemble cushions of thickened submucosa. These cushions contain a vascular complex that includes arteriovenous communications. The submucosal cushions are normally located, even in children, in the left midlateral, the right anterolateral, and the right posterolateral positions in the anal canal. Thomson postulated that hemorrhoids represent normal anal submucosal cushions that, for some reason, have been displaced in a downward direction. The cause of this displacement may be constipation combined with chronic straining during defecation, although proof for this hypothesis is lacking.
KeywordsAnal Canal Anal Fissure Dentate Line Rectal Mucosa Internal Sphincter
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