The buccal mucosa is a part of the oral mucosa with a dense structure, abundant submucosal capillaries, and high elasticity. Diseases such as oral ulcers and leukosis can damage this tissue. 1. The epithelial tissue covering the oral cavity can be divided into buccal mucosa, sublingual mucosa and other parts of the buccal mucosa is located on both sides of the oral cavity, the area is relatively larger than other parts of the oral mucosa, and elasticity is good by the oral movement of the influence of small. The buccal mucosa is rich in capillaries below the mucosa, and because the buccal mucosa has a certain degree of permeability, the buccal mucosa on both sides of the oral cavity can be used as one of the drug absorption pathways. 2. Although the normal buccal mucosa has a certain degree of permeability, but the organization is very tight. When oral ulcers, leukosis and other diseases occur, there will be buccal mucosa and other oral mucous membrane breakage, edema, pain and other manifestations. It is recommended to go to the hospital in time when symptoms of these diseases occur.