Definition
An air sac is a hollow, air-filled structure, especially in the lungs of birds and some other animals. 🐦 In birds, air sacs are connected to the lungs and help with respiration, allowing for a continuous flow of oxygen. In humans, alveoli are tiny air sacs in the lungs where gas exchange occurs. Think of them like tiny balloons that inflate and deflate with each breath. They are crucial for getting oxygen into the bloodstream and carbon dioxide out. Air sacs make breathing possible!