Final answer:
The alveoli are the first structures to receive carbon dioxide from the blood during exhalation, where gas exchange occurs before carbon dioxide is breathed out.
Step-by-step explanation:
The first structure to receive carbon dioxide from the blood during exhalation is the alveoli. Carbon dioxide is transported from body cells to the lungs via the bloodstream. The heart pumps deoxygenated blood, rich in carbon dioxide, through the pulmonary artery to the lungs. Within the lungs, these arteries branch out into a network of capillaries that create a respiratory membrane with the alveoli. This is where gas exchange occurs, and the carbon dioxide diffuses from the blood into the alveoli. The carbon dioxide then follows the path through the respiratory system to be exhaled out of the body.