The digestive system is similar to that of the ascarid in that it does have a complete digestive system and it is parasitic. The hookworm has six lips that surround the mouth opening as well as the buccal cavity that leads from the mouth to the esophagus.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.