Exchange Surfaces In The Lungs

Cartilage - Provides strength to the trachea and the bronchus. Holds open the airways so there is very little resistance to the flow of air.

Smooth Muscle - Contract to narrow the airways.

Goblet Cells - Secrete the mucus. The mucus traps microorganisms and dust.

Elastic Fibers - Stretch when breathing in (lungs inflate) and recoilwhen exhaling (breathing out to help force air out of the lungs)

Ciliated Cells - Move (or Waft) mucus up the airways to the back of throat, where it can be spat out or swallowed and digested in the stomach.

Squamous Epithelium - Gives a short diffusion pathway for Oxygenand Carbon Dioxide in the alveoli.