Skeletal muscles

Skeletal muscles are voluntary muscles that control nearly every action a person intentionally performs. They are attached to the bones of the skeleton, and typically work in pairs to move the body.

Structure

Skeletal muscles are composed of long, cylindrical cells called muscle fibers. These fibers are packed together in bundles, or fascicles, which are surrounded by a layer of connective tissue called the perimysium. Each individual muscle fiber is also surrounded by a layer of connective tissue called the endomysium.

The muscle fibers themselves are made up of smaller units called myofibrils, which are composed of even smaller structures called sarcomeres. Sarcomeres are the basic functional units of muscle tissue, and are responsible for the muscle's ability to contract and relax.

Function

The primary function of skeletal muscles is to produce movement. They do this by contracting in response to nervous system signals. When a muscle contracts, it pulls on the bone it's attached to, causing that bone to move.

Skeletal muscles also play a role in maintaining posture and body temperature. When muscles contract, they generate heat, which helps to maintain the body's temperature.

Types of Skeletal Muscles

There are three types of skeletal muscles: Type I, Type IIa, and Type IIb. Type I fibers are slow-twitch, fatigue-resistant fibers that are used for endurance activities. Type IIa fibers are fast-twitch, fatigue-resistant fibers that are used for activities that require a mix of endurance and power. Type IIb fibers are fast-twitch, fatigable fibers that are used for short, intense bursts of power.

Diseases and Disorders

There are many diseases and disorders that can affect the skeletal muscles, including muscular dystrophy, myasthenia gravis, and rhabdomyolysis. These conditions can cause a variety of symptoms, including muscle weakness, pain, and fatigue.

See Also

• Muscular system
• Muscle contraction
• Muscle tissue

Skeletal muscles Resources
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