Why are lungs divided into very small sac like structure
LUNGS are divided into bronchitis and then further divided into bronchioles. These bronchioles are further divided into small sac like structures called as alveoli. These alveoli help in incres the surface area so that the gaseous exchange takes place smoothly and efficiently . As the carbon dioxide from the impure blood is brought to lungs it is replaced with oxygen and this oxygen is absorbed by the thin walled capillaries that are present at the surface of the alveoli and then circulated in the body through blood.