Mucus:A slimy substance produced by mucous membranes and glands for lubrication and protection against particles and pathogens.
Epithelial Tissue:The layer of cells that forms the covering or lining of all internal and external body surfaces, involved in protection, secretion, absorption, excretion, filtration, diffusion, and sensation.
Mucous Membrane: A membrane lining various cavities in the body and covering internal organs, which secretes mucus for protection and lubrication