A tissue is a group of specialized cells which all strive towards the same function within an organism. Tissues are the second level in the hierarchy of cells, cell being the first, then tissue, followed by organ, organ system, and finally organism. There are as many different tissues as there are cells in the body of the organism. They are different in their shapes, designs, and function. The cells in nervous tissue resemble wiry, elongated structures, capable of transmitting electrical messages to and from the brain. The flat, tile-like design of epithelial cells in epithelial tissue make them ideal for their function, which is to serve as a protective covering, both internally and externally. Similar tissues striving towards the same common goal combine to make organs, such as the heart, or the brain. Similar organs that serve the same purpose combine together to make systems like the nervous system, or the digestive system. Finally, all the systems combined together that work towards the good health and survival of an organism is said to be just that, an organism.
Living things have different levels of organization. For instance, ameba are single-celled organisms. All their life processes are carried out within their one cell. They do not contain the level of organization of tissues. However, other organisms are more complex. When cells of the same type group together to carry out a life function, or to do a particular job, they are known as a tissue. A concrete example of this would be epithelial tissue. This is the tissue found in the lining of various parts of the human body--the cheek cells in the mouth are an example. Another type of tissue is epidermal tissue--the tissue of the skin which protects the body. There is nerve tissue found in the brain and nerves and made of neurons, or nerve cells. Blood is the largest tissue in the body, composed of red blood cells, white blood cells and platelets found in an extracellular matrix. Its function is to transport materials in the body and is a type of connective tissue. Muscle tissue, which aid in movement, is another type of tissue. To summarize, cells of the same type and origin work together and form a tissue. There are many different types of tissue in the human body.
A group of specialized cells working together forms a tissue. A group of muscle cells, for example is called muscle tissue.
There are four types of tissue:-
- Muscle tissue
- Nerve tissue
- Epithelial tissue
- Connective tissue
Muscle tissue is responsible for movement. Nerve tissue is responsible for the nervous system. Epithelial tissue is responsible for covering. Connective tissue is related to support.