Nutrient exchange is a continuous cycle, constantly supplying the body with oxygen and nutrients while removing carbon dioxide and metabolic waste.

Red blood cells are the cells in the blood that carry oxygen from the lungs to the body tissues through blood pumped by the heart. As they travel away from the heart, they traverse smaller and smaller arteries, finally arriving at the collections of microscopic blood vessels called capillaries.

Capillaries contain a high concentration of oxygen and nutrients, while the surrounding tissues contain a lower concentration. Through a process called diffusion, these particles leave the capillaries and enter the body’s tissues.

Conversely, the body’s tissues contain high concentrations of carbon dioxide and metabolic waste, while the capillaries contain a lower concentration. Waste products diffuse from the tissues into the capillaries and from there are carried by the venous system back toward the heart.

The waste products are eventually eliminated from the bloodstream by the liver, kidneys, and lungs.