Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.
Physical
Skeletal Muscle
Skeletal muscle is the striped muscle tissue attached to bones by tendons that lets the body move and hold its posture.
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The idea
Skeletal muscle is one of the three types of muscle tissue in animals with backbones. The other two are cardiac muscle in the heart and smooth muscle in organs such as the stomach. Skeletal muscles are usually attached to bones by tough cords called tendons. Under a microscope, the tissue looks striped.
Each muscle is built from bundles of long cells called muscle fibers. These cells are much longer than other muscle cells and have many nuclei, because they form when smaller cells fuse together. Inside each fiber are thin threads made of the proteins actin and myosin, arranged in repeating units called sarcomeres. When a muscle contracts, these filaments pull past each other and shorten the fiber.
Muscles get most of their energy by burning fats and carbohydrates, which makes a molecule called ATP that powers the movement. Skeletal muscle makes up about 35% of the human body by weight. Its jobs include moving the body, holding posture, helping control body temperature and keeping joints steady.
Check yourself
Question 1 of 2
About how much of the human body's weight is skeletal muscle?
Composition
what it's made of
- Tendons — Tough connective tissue that usually attaches skeletal muscles to bones.
- Fascicles — Bundles of muscle fibers grouped together inside a muscle.
- Muscle fibers — Long cells with many nuclei that do the work of contracting.
- Sarcomeres — Repeating units of actin and myosin filaments, the basic contracting units of a fiber.
- Fascia — A connective tissue layer that wraps each fiber and each muscle.
Connection
how it relates
Under Muscular System
Change
how and why it evolves
- Past
- Before birth, each muscle fiber forms when many smaller cells called myoblasts fuse together in a process called myogenesis.
- Now
- Scientists now also treat skeletal muscle as an endocrine organ, because it releases many different proteins and other substances into the body.
- Next
- Research on muscle fibers, the other cells in muscle and muscle's hormone-like signals may lead to better care for injuries and age-related muscle loss.