question_answer 61)

  Explain the digestive system of cockroach with the help of a labeled sketch.

Answer:

                  The alimentary canal present in cockroach is divided into three regions that foregut, mid gut and hindgut. (i) Foregut includes mouth cavity, pharynx, esophagus, crop and gizzard. (ii) Mouth cavity is a small space, surrounded by mouth parts. Food is crushed and actedupon by the salivary secretion in mouth. (iii) The mouth opens into a short tubular pharynx, leading towards the narrow tubularpassage called esophagus into a sac-like structure called crop which acts as astorage organ. (iv) The crop is further followed by gizzard (proventriculus). Gizzard the structurecomposed of thick circular muscles and thick inner cuticle forming six highly chitinousplates called as teeth. It associated with the grinding and crushing of food particles. Entire for gut is lined by a thick cuticle. (v)Mid gut or mesentron is about one-third middle part of alimentary canal. The internallining of mid gut is an endodermal epithelium of columnar cells raised into several smallvilli like folds. (vi) Anterior most part of mid gut surrounding the stomadaeal valve is called cardiac and finger like blind processes are called as enteric or hepatic caeca, present the junctionof foregut and mid gut. (vii) A ring of yellow filamentous structures formed between the mid gut. and hindgut arecalled Malpighian tubules help in the removal of excretory products from haemolymph. (viii) Hindgut is the remaining one-third posterior part of alimentary canal. It is relatively thicker than the mid gut is lined by cuticle and ectodermal epithelium. (ix) Hindgut is differentiated into three parts, i.e., anterior ileum, middle, colon and posteriorrectum. Ileum is short and relatively narrower and its cuticle bears minute spines. Colon is the longest, relatively thicker and a coiled part of hindgut. Rectum is a smalland oval chamber that opens out through anus.