The posterior part of the middle esophagus is the posterior esophagus. There are 10–15 Malpighian ducts at the junction of the middle and posterior alimentary canals. The posterior alimentary canal consists of four parts. Ileum, colon, rectum and anus. Dr. Siddiq Publications
(i) Ileum: Ileum is narrow, short and tube like part. Its inner wall is furrowed and folded. These folds act like eyelids. Ileum digests food and absorbs nutrients.
(ii) Colon: The long irregular portion next to the ileum is called the colon. The diameter of the colon is greater than that of the ileum. It absorbs food.
(iii) Colon: The most posterior part of alimentary canal is called colon. It is swollen and thick-walled. Its inner wall has 6 folds. These folds are called rectal papillae. It absorbs excess water, mineral salts, amino acids etc. from stool. It also stores the undigested part of the food.
(iv) Anus: The opening at the end of the rectum is called the anus. It removes waste food from the body.