Which of these is the name of the inside lining of the cheeks and floor of the mouth?

The oral mucosa is the mucous membrane lining the inside of the mouth. It comprises stratified squamous epithelium, termed "oral epithelium", and underlying connective tissue.

Buccal mucosa, the inside lining of the cheeks and floor of the mouth; part of the lining mucosa.

The buccal mucosa contains approximately 40 cm2 of mucosal surface on each side of the oral vestibule.

The oral cavity has sometimes been described as a mirror that reflects the health of the individual. Changes indicative of disease are seen as alterations in the oral mucosa lining the mouth, which can reveal systemic conditions, such as diabetes or vitamin deficiency, or the local effects of chronic tobacco or alcohol use. The oral mucosa tends to heal faster and with less scar formation compared to the skin. The underlying mechanism remains unknown, but research suggests that extracellular vesicles might be involved.