mucous membrane 
noun
An epithelial tissue which secretes mucus, and lines many body cavities and tubular organs including the gut and respiratory passages.The airways also become inflamed with swelling of the bronchial mucous membrane and secretion of excessive thick mucus that is difficult to expel....
- As powder is inhaled, it can sensitize an individual through the mucous membranes of the respiratory tract.
- These fumes are toxic and may have irritating effects on mucous membranes of the respiratory tract and eyes.