An extracellular region part that consists of a protective layer of mucus secreted by epithelial cells lining tubular organs of the body such as the colon or secreted into fluids such as saliva. Mucus is a viscous slimy secretion consisting of mucins (i.e. highly glycosylated mucin proteins) and various inorganic salts dissolved in water, with suspended epithelial cells and leukocytes.
extracellular proteinaceous gel