The outer surface of the free gingiva, the papillae and the attached gingiva function mainly as protective tissues and the epithelium is mainly keratinized. Therefore, the description of the tissue on the outer surface of the free gingiva, the papillae and the attached gingiva is stratified squamous keratinized epithelium.
The inner surface of the free gingival margin extending apically (sulcus) is nonkeratinized. Therefore, the sulcular epithelium is described as stratified squamous.
The gingival connective tissue consists of a dense network of collagen fibers. Collagen fibers function to provide firmness to the gingiva and to attach the gingiva to the underlying cementum and alveolar bone. The connective tissue of the gingiva is also rich in blood, lymphatic vessels, nerves, and many cells specific to inflammation and vascularity.1