where does mucus come from

Mucus is a normal, slippery, stringy fluid substance produced by many lining tissues in the body. It is primarily produced by specialized cells called goblet cells and submucosal glands located in the lining tissues of multiple organs, including the lungs, sinuses, mouth, throat, nose, and gastrointestinal tract. These cells secrete mucus continuously to keep these organs moist, protect their surfaces, trap irritants like dust and bacteria, and support immune defense with antibodies and enzymes. The body produces about 1 to 1.5 liters of mucus daily, mostly unnoticed unless production increases due to illness or irritation. Mucus consists mainly of water, mucin proteins secreted by goblet cells, salts, fats, immune molecules, and other substances that help protect tissues and maintain moisture.