Muscle Tissue

What are the principal types of muscle tissue?

Despite the fantasies of Hollywood horror films, a skeleton cannot move by itself. That's the job of the muscular system. Naturally, this system includes the large muscles in your arms and legs. However, it also includes thousands of tiny muscles throughout the body that help to regulate blood pressure and move food through the digestive system. In fact, muscles power every movement of the body—from a leap in the air to the hint of a smile.

Muscle tissue is found everywhere in the body—not just right beneath the skin but also deep within the body. Not only is muscle tissue found where you might least expect it, but also there is more than one kind of muscle tissue. There are three different types of muscle tissue: skeletal, smooth, and cardiac. Each type of muscle, shown in Figure 32–6, is specialized for specific functions in the body. Skeletal muscle is often found, as its name implies, attached to bones, and it is usually under voluntary control. Smooth muscle is found throughout the body and is usually not under voluntary control. Cardiac muscle makes up most of the mass of the heart, and, like smooth muscle, it is not under voluntary control.

In Your Notebook Make a two-column chart to describe the three types of muscle tissue. Label the first column Type and the second column Function.

FIGURE 32–5 Muscles in Action This pole-vaulter's skeletal muscles are clearly defined as she propels herself forward.