The nematode digestive system is generally separated into three parts, the stomodeum, intestine, and proctodeum. The stomodeum consists of the âmouth and lipsâ, buccal cavity, and the pharynx (esophagus).Each of these regions are used extensively in taxonomy as well as classification of nematodes, and for providing as indication of feeding habit or trophic group.he stomodeum consists of the âmouth and lipsâ, buccal cavity, and the pharynx (esophagus). Each of these regions are used extensively in taxonomy as well as classification of nematodes, and for providing as indication of feeding habit or trophic group.