HESI Next Generation Practice Exam 2026 - Free Practice Questions and Study Guide

Gas transport to tissues and removal of CO2 is carried out by the circulatory system. Blood picks up oxygen in the lungs, where it binds to hemoglobin in red blood cells, and then the heart pumps this oxygen-rich blood through arteries to every tissue. Cells use that oxygen for metabolism and generate carbon dioxide as a waste product, which is carried back to the lungs in the blood—mostly as bicarbonate in plasma, with some dissolved CO2 and carbaminohemoglobin—where it’s exhaled. The lungs provide the site of exchange with the outside environment, but moving gases between the lungs and tissues is the job of the circulatory system. Other systems support bodily functions, but they don’t primarily transport oxygen and carbon dioxide.