http://www.ck12.org Chapter 1. Human Biology
Organization of Your Body: Cells, Tissues, Organs
Cellsare grouped together to carry out specific functions. A group of cells that work together form atissue. Your
body has four main types of tissues, as do the bodies of other animals. These tissues make up all structures and
contents of your body. An example of each tissue type is pictured below (Figure1.1).
FIGURE 1.
Your body has four main types of tissue: nervous tissue, epithelial tissue, connective tissue, and muscle tissue.
They are found throughout your body.1.Epithelial tissueis made up of layers of tightly packed cells that line the surfaces of the body. Examples of
epithelial tissue include the skin, the lining of the mouth and nose, and the lining of the digestive system.
2.Connective tissueis made up of many different types of cells that are all involved in supporting and binding
other tissues of the body. Examples include tendon, cartilage, and bone. Blood is also classified as a
specialized connective tissue.
3.Muscle tissueis made up of bands of cells that contract and allow movement.
4.Nervous tissueis made up of nerve cells that sense stimuli and transmit signals. Nervous tissue is found in
nerves, the spinal cord, and the brain.Groups of Tissues Form Organs
A single tissue alone cannot do all the jobs that are needed to keep you alive and healthy. Two or more tissues
working together can do a lot more. Anorganis a structure made of two or more tissues that work together. The
heart (Figure1.2) is made up of the four types of tissues.