The structure of the digestive system of roundworm is very simple. The Pharynx alimentary canal is formed of mouth aperture, buccal cavity, pharynx and intestine. Mouth is situated at the anterior end of the body. Mouth aperture opens into the buccal cavity. The pharynx is situated behind the buccal cavity. The pharynx is somewhat bulk muscular and divided into three chambers.
With the help of the pharynx the roundworm sucks food materials from the intestine of its host-body and gets nutrition. Behind the pharynx is situated the narrow intestine. Posteriorly the intestine joins the rectum. The rectum opens outside through the cloacal aperture.
Fig: Digestive system of roundworm
Roundworm has no digestive gland. As they directly absorb simple liquid food from the body of the host they do not require digesting it further.