عضلة القلب
Cardiac muscle tissue, is found only in the walls of the heart as myocardium, and is involuntary being controlled by the autonomic nervous system. Cardiac muscle tissue is striated like skeletal muscle, containing contractile units called sarcomeres in highly regular arrangements of bundles. While skeletal muscles are arranged in regular, parallel bundles, cardiac muscle connects at branching, irregular angles known as intercalated discs.