Muscles

Humans have different types of muscles that allow us to move body parts and organs. In total, there are more than 600. But what exactly is a muscle, and what are muscles made of?

Voluntary and involuntary muscles

A distinction can be made between voluntary and involuntary muscles. Skeletal muscles fall under voluntary muscles. We can contract these consciously, allowing us to move or stabilize joints. This does not apply to involuntary muscles. Examples of involuntary muscles include the muscles in the stomach and intestines. The heart muscle is also an involuntary muscle.

Skeletal muscles

Within physical therapy, skeletal muscles are particularly important. They enable us to perform everyday activities such as walking, household tasks, and sports. They also help maintain a certain posture for extended periods.

A skeletal muscle is made up of a large number of muscle fibers running from one tendon to the other. The sarcomeres within a muscle fiber have the ability to slide into each other and thereby shorten. This happens when we contract a muscle. A contracted muscle therefore becomes thicker. The more force a muscle generates, the more muscle fibers slide into each other. When the muscle relaxes, the muscle fibers slide apart again, and it becomes longer and slimmer.

There are also blood vessels in the muscle that ensure the muscle receives sufficient oxygen and nutrients. In addition, the ends of the nerves ensure that the muscle receives the signal to contract or relax.

Connective tissue of the muscles

Several layers of strong connective tissue keep the muscle fibers together. These layers are:

• The endomysium, which surrounds each individual muscle fiber.
• The perimysium, which surrounds a bundle of muscle fibers.
• The epimysium, which surrounds the entire muscle.

All the connective tissue of the muscle comes together at the ends of the muscle and forms the tendons.

Types of muscle fibers

Although muscles may look very similar at first glance, different types of muscle fibers can be distinguished. For example, there are muscles that must have good endurance because they are loaded for a long time. These are the type I fibers. Muscles that are more powerful and explosive consist of type IIb fibers. Type IIa fibers are somewhat in between.

There is usually a mix of fiber types. The ratio between these muscle fibers differs from person to person. The composition depends, among other things, on the muscle, training status, and genetic factors.

Muscles often owe their names to, for example, their function, location, length, or shape. These names are usually given in Latin.