Hemorrhoids are cushions of arteriovenous channels, located above the pectinate line in a circular manner. They contribute to fecal continence. Anatomically, they can be called the corpus cavernosum recti. The blood supply is provided by branches of the superior rectalr artery, which is the cause for the sites of predilection at 3, 4, and 11 o'clock (patient supine).Contraction of the sphincter ani internus muscle inhibits venous drainage. This leads to a "spongy" enlargement of the arteriovenous cushions, which allows continence for fluids and gases.Pathological hemorrhoids occur if further enlargement of the hemorrhoids occurs, causing symptoms.
