To hear audio pronunciation of this topic, purchase a subscription or log in.

[act + -in]
One of the contractile proteins that make up the sarcomeres of muscle tissue. During contraction, the actin filaments are pulled toward the center of the sarcomere by the action of myosin filaments, and the sarcomere shortens. Actin is also found in the cytoskeleton of many kinds of cells, where it contributes to cell shape and movement.

There's more to see -- the rest of this topic is available only to subscribers.