1. Gingival epithelium:
The gingival epithelium comprise the epithelial tissue that covers the external surface of the gingiva as well as the epithelium lining the gingival sulcus and the junctional epithelium (Fig. 9).
Fig. 9 (Section courtesy of Dr. H.E. Schroeder): The gingival epithelium is subdivided into 3 sections, the oral epithelium (OE), the sulcular epithelium (SE), and the junctional epithelium (JE). The oral epithelium extends from the mucogingival junction to the gingival margin. It is continuous with the sulcular epithelium that lines the lateral aspect of the gingival sulcus. The junctional epithelium forms the dentoepithelial junction apical to the sulcus. Its coronal end forms the bottom of the gingival sulcus and is overlapped by the sulcular epithelium. These epithelia differ from one another in their function and, therefore, in some of their histological characteristics.
a. Oral epithelium
It is the stratified, squamous keratinizing epithelium, that lines the vestibular and oral surfaces of the gingiva. It extends from the mucogingival junction to the gingival margin (see Fig. 1), except for the palatal surface where it blends with the palatal epithelium (see Fig. 7).
Fig. 10: The oral epithelium consists of a basal layer (stratum basale, SB), a spinous layer (stratum spinosum, SS), a granular layer (stratum granulosum, SG) and a cornified layer (stratum corneum, SC). It is designed primarily for protection against mechanical injury during mastication. Resistance to mechanical injury is mediated primarily by the numerous intercellular junctions, mostly desmosomes, that hold the cells tightly together and the cornified layer. The cornified layer and the relatively narrow intercellular spaces also contribute to the relative lack of permeability.
Fig. 11 (From Karring, T. and Löe, H., 1970): The oral epithelium is connected to the underlying connective tissue of the lamina propria by an irregular interface. This interface consists of finger-like projections of connective tissue from the papillary layer (arrows, Fig. 11 A) extending into depressions on the undersurface of the epithelium. These depressions (Fig. 11 B) are located between the interconnected Rete ridges that form the undersurface of the epithelium. Cross-sections of these ridges, as seen in histological sections are sometimes referred to as Rete pegs.
Fig. 12: Transmission electronmicrograph of the junction between a basal cell of the gingival oral epithelium and the connective tissue of the underlying lamina propria. The epithelial cell (EC) contains widely dispersed cytoplasmic filaments, also known as tonofilaments.
The epithelial cell membrane facing the lamina propria is studded with numerous hemidesmosomes (HD) and is connected to it by a basal lamina (BL). The basal lamina consists of an electron-dense layer, the lamina densa (LD) and an electron-lucent layer, the lamina lucida (LL). The lamina densa is composed of an afibrillar type of collagen, type IV collagen. The lamina lucida is composed of laminin and other glycoproteins. Anchoring fibrils (AF), composed of type VII collagen, extend from the undersurface of the lamina densa into the lamina propria.
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Created: May 8, 1999 Revised:
Max A. Listgarten: Comments to author: firstname.lastname@example.org
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