of the gingiva is presented in Figure 16.20. The gingiva is composed of two parts:  Gingival mucosa, which is synonymous with the masticatory mucosa described above  Junctional epithelium, or attachment epithelium, which adheres firmly to the tooth. A basal lamina-like material is secreted by the junctional epithelium and adheres firmly to the tooth surface. The cells then attach to this material via hemidesmosomes. The basal lamina and the hemidesmosomes are together referred to as the epithelial attachment. In young individuals, this attachment is to the enamel; in older individuals, where passive tooth eruption and gingival recession expose the roots, the attachment is to the cementum.
FIGURE 16.18 • Golgi apparatus in an odontoblast. This electron micrograph shows a region of the Golgi apparatus containing numerous large vesicles. Note the abacus bodies (arrows) that contain parallel arrays of filaments studded with granules. 52,000.
Above the attachment of the epithelium to the tooth, a shallow crevice called the gingival sulcus is lined with crevicular epithelium that is continuous with the attachment epithelium. The term periodontium refers to all the tissues involved in the attachment of a tooth to the mandible and maxilla. These include the crevicular and junctional epithelium, the cementum, the periodontal ligament, and the alveolar bone.
The major salivary glands are paired glands with long ducts that empty into the oral cavity.
The major salivary glands, as noted above, consist of the paired parotid, submandibular, and sublingual glands. The parotid and the submandibular glands are actually located outside the oral cavity; their secretions reach the cavity by ducts. The parotid gland is located subcutaneously, below and in front of the ear in the space between the ramus of the mandible and the styloid process of the temporal bone. The submandibular gland is located under the floor of the mouth, in the submandibular triangle of the neck. The sub-lingual gland is located in the floor of the mouth anterior to the submandibular gland.
The minor salivary glands are located in the submucosa of different parts of the oral cavity. They include the lingual, labial, buccal, molar, and palatine glands.
Each salivary gland arises from the developing oral cavity epithelium. Initially, the gland takes the form of a solid cord of cells that enters the mesenchyme. The proliferation of epithelial cells eventually produces highly branched epithelial cords with bulbous ends. Degeneration of the innermost
FIGURE 16.19 • Odontoblast process of a young odontoblast. This electron micrograph shows a process of the odontoblast entering a dentinal tubule. The process extends into the predentin and, after passing the mineralization front (arrows), lies within the dentin. The collagen fibrils in the predentin are finer than the more mature, coarser fibrils of the mineralization front and beyond. 34,000.
FIGURE 16.20 • Schematic diagram of gingiva. This schematic diagram of gingiva corresponds to the rectangular area of the orientation diagram. The gingival epithelium is attached to the enamel of the tooth. Here, the junction between epithelium and connective tissue is smooth. Elsewhere, the gingival epithelium is deeply indented by connective tissue papillae, and the junction between the two is irregular. The black lines represent collagen fibers from the cementum of the tooth and from the crest of the alveolar bone that extend toward the gingival epithelium. Note the shallow papillae in the lining mucosa (alveolar mucosa) that contrast sharply with those of the gingiva.
cells of the cords and bulbous ends leads to their canalization. The cords become ducts, and the bulbous ends become secretory acini.