Inside the lungs are sac-like objects called?

The sac-like objects inside the lungs are called alveoli. Alveoli are tiny, balloon-shaped structures that line the inner walls of the lungs. These microscopic air sacs are where gas exchange takes place between oxygen and carbon dioxide. The oxygen we breathe in diffuses across the thin walls of the alveoli into the bloodstream, while carbon dioxide, a waste product of metabolism, diffuses from the bloodstream into the alveoli to be exhaled. The large surface area provided by the numerous alveoli in the lungs facilitates efficient gas exchange, enabling the respiratory system to supply oxygen to the body and remove carbon dioxide.