What kind of muscle is the heart mainly composed of?
nerve muscle
respiratory muscle
idealized muscle
cardiac muscle
To move blood through the heart, the cardiac muscle needs to contract in an organized way. Blood first enters the atria ( Figure below ). When the atria contract, blood is pushed into the ventricles. After the ventricles fill with blood, they contract, and blood is pushed out of the heart. The heart is mainly composed of cardiac muscle. These muscle cells contract in unison, causing the heart itself to contract and generating enough force to push the blood out.