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, the urethra, and various other organs.  In addition, the covering of the glans penis (head of the penis) and the inside of the prepuce (foreskin) is mucous membrane, not skin.
See also:
 
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