Q.(a) Explain the digestive system of Periplaneta americana. OR

The cockroach's (Periplaneta americana) digestive system is divided into foregut, midgut, and hindgut — food is ingested and stored/ground in the foregut, digested and absorbed in the midgut (aided by gastric caeca), and water is reabsorbed before waste is eliminated in the hindgut.

The alimentary canal of the cockroach is a long tube divided into three histologically and functionally distinct regions:

1. Foregut (Stomodaeum): lined internally by cuticle (of ectodermal origin). Consists of the mouth, buccal cavity, pharynx, a narrow oesophagus, and then the crop — a large sac-like region that stores ingested food temporarily. Following the crop is the gizzard (proventriculus), a muscular chamber lined with chitinous teeth/plates that mechanically grinds the food into fine particles before it passes to the midgut. A pair of salivary glands (with a salivary reservoir) opens into the buccal cavity/pharynx region, secreting saliva that lubricates food and begins starch digestion. …