Hemorrhoids are primarily a varicose condition of the hemorrhoidal veins, and their tumor-like structure is due to this varicosity (Fig. 1).
They are located on the inner side of— and project into—two similar, hollow, flexible, distensible, collapsible, sensitive and musculovascular cones (Fig. 2). These cones are formed by the coalescence of the hindgut and proctodeum, with their common point of intersection at the pectinate line. One of these is the proximal (or rectal) cone, the other, the distal (or anal) cone. The former is lined with mucous membrane, nourished by the superior hemorrhoidal artery and drained by the super i o r hemorrhoidal veins. The anal cone is lined with skin, nourished by the inferior hemorrhoidal artery and drained by the inferior hemorrhoidal veins.
Clinically, hemorrhoids should be classified: (1) according to location, (2) according to structure.
1. According to their location
PENNINGTON JR. TREATMENT OF HEMORRHOIDS BY THE OPEN METHOD. JAMA. 1915;LXIV(14):1136-1138. doi:10.1001/jama.1915.02570400018006