Heart: Tissue Function

The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries. The human circulation is composed of two circulatory systems: the pulmonary circulation, a short loop from the heart to the lungs and back again, and the systemic circulation, which [Page 526]sends blood from the heart to all the other parts of our bodies and back again.

The heart, a hollow muscular pump, is the key organ in the circulatory system, whose main function is to propel blood throughout the body. It beats from 60 to 100 times per minute, on average, but it can go much faster depending upon the need of every individual body.

Cardiac muscles require a large quantity of nourishment and oxygenation due to their constant pumping activity, ...