2.4 Muscle Tissues

There are muscle tissues and there are organs called muscles. Muscles are made up of muscle tissues. Muscle tissues and the muscles they make up are specialized to contract. Because of their ability to shorten (contract), muscles are able to produce motion.

See figure 2-3 for the three types of muscle tissue.

a. Skeletal Muscle Tissue. The cells (muscle fibers) of skeletal muscle tissue are long and cylindrical and have numerous nuclei. The arrangement of the cellular contents is very specific and results in a striated appearance when viewed with the microscope. This type of muscle tissue is found mainly in the skeletal muscles.

Figure 2-3. Types of muscle tissue.

The cells (muscle fibers) of cardiac muscle tissue are short, branched, contain one nucleus, and are striated. This tissue makes up the myocardium (wall) of the heart.

The cells (muscle fibers) of smooth muscle tissue are spindle-shaped, contain one nucleus, and are not striated. Smooth muscle tissue is generally found in the walls of hollow organs such as the organs of the digestive and respiratory systems, the blood vessels, the ureters, urinary bladder, urethra, and reproductive ducts.