Heart

The heart is a hollow muscular organ that pumps blood through blood vessels to various parts of the body by repeated, rhythmic contractions.

The heart is principally composed of cardiac muscle and connective tissue. Cardiac muscle is an involuntary striated muscle tissue specific to the heart and is responsible for the heart's ability to pump blood.

The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during a 66-year lifespan. The heart pumps approximately 4.7-5.7 liters of blood per minute. It weighs approximately 250 to 300 grams (9 to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males.