anatomical surface A two dimensional anatomical structure that is the boundary between an anatomical structure and an anatomical substance, an anatomical space or the organism's environment. Examples include the surface of your skin, the surface of the lining of your gut; the surface of the endothelium of you aorta that is in contact with blood. CARO:0000010 Old definition: "Non-material anatomical entity of two dimensions, that is demarcated by anatomical lines or points on the external or internal surfaces of anatomical structures." Note, in the new definition, the space referred to is not necessarily an anatomical space. It may be the outside of an organism. morphological boundary