Britannica Sources used in this answer

How do the respiratory and circulatory systems work together to supply oxygen to body tissues?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Diagram explaining ATP's role in powering cellular activities, with arrows showing ATP produced by mitochondria, chloroplasts, and glycolysis, and used for making biomolecules, transporting substances, and driving energy-requiring processes; includes a structural diagram of ATP with labeled adenine, ribose, and phosphate groups. — Physiology Adenosine triphosphate (ATP) is the power source of many biochemical reactions. It is produced in the cell structures and system listed at the left to energize the important life processes listed on the right. An abbreviated chemical formula of the structure of ATP is also shown. The two high-energy P―O―P bonds are responsible for its power.

The respiratory and circulatory systems function as an integrated unit to supply oxygen to body tissues, a process essential for sustaining cellular metabolism. This collaboration involves several coordinated steps:12

Gas Exchange in the Lungs

The process begins with ventilation, where the respiratory system brings atmospheric air into the lungs. Oxygen moves from the alveoli into the pulmonary capillaries via diffusion, driven by a difference in partial pressure. Once in the blood, oxygen binds primarily to hemoglobin within red blood cells.1234

Transport and Delivery

The circulatory system acts as the transport mechanism. Driven by the pumping action of the heart, oxygenated blood travels through the systemic circulation to reach tissues throughout the body. Upon reaching the peripheral capillaries, oxygen is discharged into the tissues and cells, again moving by diffusion.1563

Cellular Utilization

Once delivered, oxygen reaches the mitochondria, where it is used in aerobic metabolism to produce adenosine triphosphate (ATP), the energy currency of the cell. As a byproduct, carbon dioxide is produced and transported back through the blood to the lungs to be exhaled, completing the cycle.7136