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Cockroaches would fall under the category of insects of the Blattodea order. Around 4,600 cockroaches are living aside human habitats. The digestion of food would take place in the cavities specialized or combined together.
The Alimentary canal has been divided into three main parts:
The alimentary canal starts with the foregut which comprises the mouth and surrounding parts of the mouth. The cavity of mouth is known as pharynx. The foregut extends in the form of the oesophagus, which has a thin wall (narrow) structure. Further extension of the canal would be called a crop that has a similar structure to the oesophagus. The opening for crop called proventriculus/gizzard would be an organ that would be muscular in nature. There is a duo of glands (salivary).
Every salivary gland has branches where various secretions of different branches flow to a combined passage. The receptacle of salivary viz. reservoir that resembles a bladder is in place for both the salivary glands. These are mainly for the storage of salivary secretions. Both receptacles have a combined/common passage that is rectangular shaped that would open to the combined salivary passage. The mouth cavity near the labium is opened from the combined salivary passage. The chitin has its lining with the entire foregut. For facilitating food grinding, the chitin creates the proventricular teeth and the plate.
Midgut creates real gut viz. Mesenteron and comprises the whole stomach/ventriculus. There are six pairs of gastric (related to the stomach) caecae right at the joint of the gizzard and stomach. At the anterior end of the stomach, these are ordered in a ring-like style and pouch-like structure. The anterior lobe of every group of caecae would expand even above the proventriculus whereas the posterior lobe would extend to the ventriculus. The digestive juices flow into the stomach owing to the caecae secretion. The midgut is lined by a peritrophic membrane and not by a cuticle. The very same membrane saves the stomach wall from damage and is simultaneously fully passable for enzymes and food digested.
This gut is a coil-like structure and consists of the anterior ileum, middle colon, and posterior rectum. The final one viz. the posterior rectum has its opening to the exterior via the anus. It has a lining formed by the cuticle. There are a large number of long tubules also known as Malpighian tubules right at the joint of the stomach and ileum.
Digestion begins first at the mouth where the parts like mandibles and maxillae help to chew the food. The part named salivary carbohydrases digests food to a partial extent. The saliva juice lubricates the food and helps to swallow it. Later the food moves to the esophagus and then onto the crop. This is the point where food in its masticated form is stored temporarily. The next point where the food moves would be at the gizzard where its grinding takes place. There is a valve named stomodeal right at the joint of the stomach and gizzard.
The regurgitation of food would be prevented by this valve while ensuring smooth passage of food in the stomach. The food once entering the stomach is treated by the digestive enzymes created by the gastric caecae. The enzymes include invertase, amylase, tryptase, maltase, and lipase. The residual fats, proteins, and carbohydrates would be absorbed here.
From the above-written characteristics, one would be able to understand the complexity of digestion in Cockroaches. The subject has been a point of discussion for students of biology worldwide. Hence this topic should be certainly given its due importance.
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