What does blood take on as it passes through the lungs?

As blood passes through the lungs, it undergoes a crucial exchange of gases known as respiration. In this process, carbon dioxide, which is a waste product of metabolism, is expelled from the blood into the lungs to be exhaled. Simultaneously, oxygen from the inhaled air diffuses into the blood in the pulmonary capillaries. This exchange occurs due to the differences in partial pressures of oxygen and carbon dioxide between the alveoli (tiny air sacs in the lungs) and the blood.

The significant increase in the oxygen content of the blood after this gas exchange is essential for delivering oxygen to the body's tissues, where it is utilized for cellular respiration. Thus, as blood passes through the lungs, it "takes on" oxygen, enriching its content and preparing it to be distributed throughout the body via the circulatory system. This process highlights the lungs' critical role in ensuring that oxygen is delivered to the cells, which is necessary for sustaining life.