The main part of the digestive system is the alimentary canal which consists of the mouth, oesophagus, stomach, small intestine and large intestine.2. There are other organs associated with the alimentary canal to assist with digestion. These include the salivary glands, the pancreas, the liver and the gall bladder.) Small intestine i) The small intestine is the longest section of the alimentary canal (about 6 metres) and consists of three segments forming a passage from the stomach to the large intestine.