A tissue is a group of cells that have a common embryonic origin and function together to carry out specialized activities.

There are four basic types of tissues in the human body, and they are categorized according to their structure and function:

1. Epithelial tissue lines the surfaces of the body and protects it from the environment. It also helps to absorb and secrete substances.
2. Connective tissue supports and binds other tissues together. It also stores fat and provides immunity.
3. Muscle tissue allows the body to move.
4. Nervous tissue transmits signals throughout the body and controls body functions.

Epithelial tissue mimics the outer layer of the embryo, which is called the ectoderm.

Types of tissues:

1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nervous tissue

The function of each type of tissue is:

• Epithelial tissue: Protection, absorption, secretion, and diffusion
• Connective tissue: Support, binding, storage, immunity
• Muscle tissue: Movement
• Nervous tissue: Communication and control

Tissues work together to form organs and organ systems. For example, the skin is an organ that is made up of epithelial tissue, connective tissue, and muscle tissue. The skin protects the body from the environment, regulates temperature, and helps to produce vitamin D.