The<unk>  is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions, or a similar structure in the annelids, mollusks, and arthropods. The term cardiac (as in cardiology) means "related to the<unk> " and comes from the Greek καρδία, kardia, for<unk> ." The<unk>  is composed of cardiac muscle, an involuntary muscle tissue which is found only within this organ. The average human<unk>  beating at 72 BPM, will beat approximately 2.5 billion times during a lifetime of 66 years.
Heart
Brain
Airway
Central nervous system
Cardiac muscle
Thyroid gland
Head 
Pulmonary circulation