In animal anatomy, the mouth is the first portion of the alimentary canal that receives food. The adjectival form is “buccal” derived from Latin bucca (lit. “cheek”), hence “buccal cavity”, “buccal nerve”, “buccal artery”, etc. Some animal phyla, including vertebrates, have a complete digestive system, with a mouth at one end and an anus at the other. Which end forms first in ontogeny is a criterion used to classify animals into protostome and deuterostome.