The mucous membranes (or mucosa) are linings of ectodermic origin, covered in epithelium, that line various body cavities and internal organs. It is at several places continuous with skin: at the nostrils, the lips, the ears, the genitourinary area, and the anus. The viscid secretion of the mucous membranes is termed mucus (note the spelling difference).

Body cavities featuring mucous membrane include most of the respiratory tract, the entire gastrointestinal tract, including the rectum, the urethra, and various other organs. In addition, the vagina, the clitoris, the covering of the glans penis (head of the penis) and the inside of the prepuce (foreskin) is mucous membrane, not skin.

See also

• mucin
• mucocutaneous boundary