What is the primary function of cardiac muscle?

The primary function of cardiac muscle is to facilitate the contractions of the heart. Cardiac muscle is specialized tissue found only in the heart and is uniquely designed to enable the rhythmic and continuous contractions required to pump blood throughout the body. This muscle tissue has distinct properties, including automaticity, which allows it to generate electrical impulses that trigger heartbeats without requiring external nerve stimulation.

Unlike other muscle types, cardiac muscle is involuntary, meaning it operates autonomously and is not under conscious control. This ensures that critical heart functions continue to operate to maintain blood circulation and oxygen supply to vital organs.

The other options represent functions associated with different types of muscles or biological processes. For instance, the movement of limbs is primarily the function of skeletal muscle, while digestion occurs through smooth muscle contractions in the gastrointestinal tract. Lastly, organ protection is a structural role typically supported by the skeletal system rather than a muscle function. Thus, the choice identifying the contractions of the heart directly aligns with the specialized role of cardiac muscle.