Illustration of the respiratory system highlighting key components such as the trachea, bronchi, lungs, and alveoli, demonstrating how air travels through the body for gas exchange.

- The circulatory system is like a highway network made of the heart, blood, and blood vessels (arteries, veins, capillaries) that delivers oxygen and nutrients to every cell.
- The respiratory system is the oxygen supply unit that brings in fresh air and removes carbon dioxide waste; it includes the lungs, nose, trachea, bronchial tubes, and alveoli.
- Air travels from the nose or mouth down the trachea into two bronchial tubes, which branch into smaller bronchioles ending in alveoli (tiny air sacs).
- Alveoli are surrounded by capillaries where oxygen enters the blood and carbon dioxide exits during exhalation.
- The heart, about fist-sized, acts as the engine of the circulatory system, pumping blood through vessels at about 70 beats per minute.