Chitin which is the lining of alimentary canal,is modified in gizzard to form a Plate with 6 proventricular teeth. and here the second round of grinding takes place (I.e after mandibles)

In cockroach, food is crushed in the Gizzard.
The detailed solution is as follows:
1. Introduction:
- Cockroaches are insects that belong to the class Insecta and order Blattodea.
- They have a specialized digestive system to process their food.
2. Anatomy of the cockroach digestive system:
- The digestive system of a cockroach consists of several parts, including the foregut, midgut, and hindgut.
- The foregut is responsible for the initial processing of food.
3. The role of the Gizzard:
- The Gizzard is a part of the foregut in the digestive system of a cockroach.
- It is a muscular organ located between the crop and the midgut.
- The Gizzard is responsible for grinding and crushing the food into smaller particles.
4. Function of the Gizzard:
- When a cockroach ingests food, it first enters the crop, where it is temporarily stored.
- From the crop, the food then moves into the Gizzard.
- The strong muscles in the Gizzard contract and grind the food, breaking it down into smaller pieces.
- This grinding action helps in the mechanical digestion of the food.
5. Passage to the midgut:
- After the food is crushed in the Gizzard, it passes into the midgut.
- The midgut is responsible for the chemical digestion and absorption of nutrients from the food.
6. Conclusion:
- In cockroaches, the Gizzard plays a crucial role in the digestion process.
- It helps in crushing and grinding the food before it moves into the midgut for further digestion and absorption.