<P> Cells of epithelial tissue are tightly packed and form a continuous sheet . They have almost no intercellular spaces . All epithelia is usually separated from underlying tissues by an extracellular fibrous basement membrane . The lining of the mouth, lung alveoli and kidney tubules all are made of epithelial tissue . The lining of the blood and lymphatic vessels are of a specialised form of epithelium called endothelium . </P> <P> Epithelium lines both the outside (skin) and the inside cavities and lumina of bodies . The outermost layer of human skin is composed of dead stratified squamous, keratinized epithelial cells . </P> <P> Tissues that line the inside of the mouth, the oesophagus, the vagina, and part of the rectum are composed of nonkeratinized stratified squamous epithelium . Other surfaces that separate body cavities from the outside environment are lined by simple squamous, columnar, or pseudostratified epithelial cells . Other epithelial cells line the insides of the lungs, the gastrointestinal tract, the reproductive and urinary tracts, and make up the exocrine and endocrine glands . The outer surface of the cornea is covered with fast - growing, easily regenerated epithelial cells . A specialised form of epithelium--endothelium forms the inner lining of blood vessels and the heart, and is known as vascular endothelium, and lining lymphatic vessels as lymphatic endothelium . Another type, mesothelium, forms the walls of the pericardium, pleurae, and peritoneum . </P> <P> In arthropods, the integument, or external "skin", consists of a single layer of epithelial ectoderm from which arises the cuticle, an outer covering of chitin the rigidity of which varies as per its chemical composition . </P>

What type of epithelial tissue lines the mouth