Heart and Blood Flow



The heart is a large organ primarily made of muscle tissue that works continuously to move blood throughout the body. The four chambers, four valves, and four major vessels of the heart are involved in unidirectionally pumping blood from the heart to the lungs for oxygen, back to the heart, and to the rest of the body to deliver the oxygen. Contraction of the heart muscle is generated by electrical impulses created by specialized heart cells. The amount of blood the heart pumps must meet the metabolic demands of the body. There are many intrinsic and extrinsic mechanisms responsible for this regulation.

At A Glance

  • The heart consists of four chambers, four valves, and four major vessels that work to pump blood throughout the body.
  • Pulmonary circulation is blood flow through the lungs, and systemic circulation is blood flow through the rest of the body.
  • Coronary circulation is blood flow through the tissues of the heart to supply the heart muscle with oxygen and nutrients.
  • Heart muscle cells transmit electrical impulses, which cause the heart muscle to contract and move blood out of the heart.
  • The cardiac cycle is one contraction-relaxation event of the heart. During this cycle, changes in electrical activity cause the pressures and volumes of the heart chambers to change as blood moves in and out of the heart, valves open and close to direct blood flow, and heart sounds are generated from the closing of the valves.
  • Cardiac output is the volume of blood ejected from each ventricle per minute, and it is regulated by electrical and chemical factors.