There are five types of cells in the human body: epithelial, connective, nerve, muscle and adipose. Each performs its own special function and joins with other cells of the same type to form specific kinds of tissues. Tissues join together to form organs and other body parts. Each type of cell is limited to a specific function, but working together as unified structures, they allow the body to move and operate as a single unit.
Epithelial Cells
Epithelial cells are flattened, thin cells that lie against each other tightly like tiles in a floor. They line surfaces in the body and form a protective barrier. Epithelial cells make up the lining of most organs in the human body. They also form connective sheets of smooth tissue that surrounds body cavities. Skin tissue and glands are also made up of epithelial tissue.
Connective Tissue
Connective tissue cells come in different two different types. There are wandering cells called macrophages that move through tissues (usually when there is an infection or an injury), and fixed cells that stay in specific areas (such as cartilage and tendons). These cells are called fibroblasts and mast cells. Fibroblasts are large and secrete proteins into the matrix that holds the cells together. Mast cells are also large and widely distributed. They are near blood vessels and release heparin which keeps the blood from clotting.
Nerve Cells
Nerve cells have long tentacle-like extensions that spread out into the area surrounding the cells. The tips of these tentacles are close to each, but not touching. Chemicals called neurotransmitters connect the tips and transmit impulses back to the brain. Basic nerve cells are called neurons. Neuroglial cells build a support system within nervous tissue that connects everything together and provides cell-to-cell communication.
Muscle Cells
Muscle cells are long tubular cells that contract with help from nerve cells. They are slender and lie against each other like fibers in a rope. There are three types of muscle cells: striated, non-striated and cardiac. Striated muscle cells comprise the muscles that move the body, while non-striated cells form the hollow organs. Cardiac muscle cells are only found in the heart.
Adipose Cells
Adipose cells are fat cells. They are little more than tiny bubbles of fat. B-lymphocytes are white blood cells that are actually a type of adipose cell. B-lymphocytes produce antibodies that help fight infections.
References
- CUNY.edu: Basic Anatomy--Tissues & Organs
- "Hole's Human Anatomy and Physiology;" Shier, Butler & Lewis; 2007
