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Human Body Study

Cardiac Muscle

The muscle found only in the wall of the heart.

The three muscle types and the tendons that anchor them A four-panel plate: three comparative panels of skeletal, cardiac and smooth muscle drawn so the visual differences carry the classification, plus a fourth panel showing skeletal muscle attaching to bone via a tendon. Each panel links to that subject's article. Skeletal muscle long striated multinucleate fibres, attached to bones Cardiac muscle branched cells joined by intercalated discs, with a central nucleus Smooth muscle spindle-shaped cells with a single central nucleus; no striations Tendon — connection to bone a skeletal muscle's belly tapers into a cord of parallel collagen fibres, anchored into bone muscle tendon bone Three muscle types — one mechanism, three cell forms — plus the tendon, by which a skeletal muscle pulls on bone.

Structure

Section titled “Structure”

Striped like skeletal muscle, but its cells are short, branched, and joined end-to-end by special junctions (intercalated discs) that pass the electrical signal directly from cell to cell.

How it works

Section titled “How it works”

The heart generates its own rhythm from a built-in pacemaker; nerves and hormones only speed it up or slow it down. Because the cells are electrically linked, the heart contracts as a single coordinated unit.

What it does

Section titled “What it does”

Pumps blood — beating around 100,000 times a day, for a lifetime, without rest.

Key idea

Section titled “Key idea”

Cardiac muscle is involuntary, self-triggering, and extraordinarily fatigue-resistant — but it has almost no ability to regenerate, which is why heart attacks cause permanent damage.