Compare and contrast epithelial and muscle. There are at least three primary functions that are performed by the epithelial tissue. Firstly it provides a great protective covering for all the tissues lying beneath it from radiation, toxins, physical trauma, desiccation and invasion of pathogens. Secondly it helps to regulate the exchange of chemicals between the body cavity and the tissues that lie underneath the epithelial tissues. It also helps in the secretion of the hormones in to the bloods. These are all major but primary functions of the epithelial tissues. From this we can easily understand the importance of the epithelial tissues.

Epithelial tissues act as coverings, controlling the movement of materials across their surface. Connective tissue binds the various parts of the body together, providing support and protection. Muscle tissue allows the body to move and nervous tissues functions in communication.

Explanation:

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.