fundamentals
Tissues and Organs
Introduction
 are related Cells that are joined together. The cells in a tissue are not identical, but they work together to accomplish specific functions. For example, muscle tissue has muscle cells, which contract to make the muscle move. Muscle tissue also has nerve cells, which send signals to tell the muscle when to contract and relax. A sample of tissue removed for examination under a microscope (biopsy) contains many types of cells, even though a doctor may be interested in only one specific type. Connective tissue is the tough, often fibrous tissue that binds the body's structures together and provides support and elasticity. It is present in almost every organ, forming a large part of skin, tendons, joints, ligaments, blood vessels, and muscles. The characteristics of connective tissue and the types of cells it contains vary, depending on where it is found in the body. are the body's recognizable structures (for example, the heart, lungs, liver, eyes, and stomach) that perform specific functions. An organ is made of several types of tissue and therefore several types of Cells . For example, the Even an organ as apparently simple as the Gallbladder and Biliary Tract contains different types of cells, such as those that form a lining resistant to the irritative effects of bile, muscle cells that contract to expel bile, and cells that form the fibrous outer wall holding the sac together. 