A heart is a hollow, muscular organ that pumps blood through the cirulatory system
*Heart muscle tissue is called myocardium*
Vertebrate hearts are classed as myogenic, meaning the heartbeat originates in the muscle tissue (in the myocardium)
In mammalian hearts there are 4 chambers, 2 muscular ventricular chambers and 2 less muscular atria
In the human heart, blood flows from the right heart to the lungs, then from the lungs to the left heart, and from there to the systemic tissues.
The Cardiac Cycle is the of contraction and relaxation of the heart
Systole is when the ventricles contract
Diastole is whent he ventricles relax