Explanation:
An exoskeleton is an external skeleton that supports and protects an animal's body. It is composed of a variety of materials, including chitin, calcium carbonate, and other hard materials. Exoskeletons are found in a variety of animals, including insects, crustaceans, and some mollusks.

Origin of Exoskeleton:
The exoskeleton is originated from the epithelium tissue. The exoskeleton is formed by the hardening of the exoskeleton secreting cells of the epidermis. The exoskeleton is secreted by the cells of the epidermis and is a product of the epithelial tissue. In insects, the exoskeleton is formed by the secretion of chitin by the epidermal cells. The chitin is then arranged in layers and hardened to form a protective and supportive structure. In crustaceans, the exoskeleton is formed by the secretion of calcium carbonate and chitin by the epidermal cells.

Functions of Exoskeleton:
The exoskeleton has several functions, including support, protection, and muscle attachment. It provides a framework that supports the animal's body and protects it from physical damage. The exoskeleton also provides attachment sites for muscles, allowing the animal to move and perform various activities.

Advantages of Exoskeleton:
The exoskeleton provides many advantages to animals. It allows them to live in harsh environments, such as deserts, where the exoskeleton helps to prevent water loss. It also protects against predators and parasites, and can act as camouflage. The exoskeleton also provides support and allows animals to move more efficiently.

Disadvantages of Exoskeleton:
However, the exoskeleton also has some disadvantages. It is heavy and can limit an animal's mobility. It can also restrict growth, as the animal must shed its exoskeleton in order to grow. This process of shedding and forming a new exoskeleton is called molting and can leave the animal vulnerable to predators.

Conclusion:
In conclusion, the exoskeleton is an external skeleton that supports and protects an animal's body. It is formed by the epithelial tissue and provides many advantages to animals, including support, protection, and muscle attachment. However, it also has some disadvantages, including limiting mobility and restricting growth.

Exoskeleton is originated from epithelial cell and after origin it's keratinized.