Haemorrhoids

Abstract

The anal canal submucosa forms a series of ‘cushions’. The three main cushions are found in the left lateral, right posterior and right anterior positions (3, 7 and 11 o’clock). They consist of venous dilatations surrounded by a network of smooth muscle, elastic and fibrous tissue, as well as the overlying mucosa. The submucosal smooth muscles are anchored to the internal sphincter and the longitudinal muscle passing through the internal sphincter fasciculi. This network of muscle supports the anal canal lining during defecation. It returns the anal canal lining to its initial position after the temporary downward displacement in defecation.