In plants, cellulose is a rigid tube that allows plants to maintain their form, which similar structure and support system is found in insects?

Exoskeleton and Endoskeleton

Multicellular organisms e.g. man  meet their needs through use of specialized  systems that they have in their bodies. Examples of such include:
1. cardiovascular system composed of heart, veins and  arteries which facilitate transport of nutrients to all parts of the body .
2. Skeletal system composed of bones, joints, ligaments and cartilage whose function is support and protection of the body.
3. Digestive system composed of mouth, esophagus, stomach , small and large intestines whose function is breakdown of food and absorption of nutrients.

Honestly isn't the place to ask that. search it up on google or something. that's the best answer i can give you.