Anatomy & Physiology

Anatomy & Physiology Study Guide Oral mucosa lines the oral cavity which has a stratified squamous epithelium. Nutrients are not absorbed in the oral cavity; however, the mucosa inferior to the tongue is thin enough and vascular enough to permit the rapid absorption of lipid-soluble drugs. Also, pads of fat and the buccinator muscles support the mucosae of the lateral walls in the oral cavity (the cheeks). Anteriorly, the mucosa of each cheek is continuous with that of the lips, or labia . The space between the lips, cheeks, and teeth is known as the vestibule . The gingivae , or gums, are ridges of the oral mucosa that surround the base of each tooth on the alveolar processes of the maxillary bones and mandible. The hard and soft palates form the roof of the oral cavity. The floor of the mouth inferior to the tongue receives extra support from the geniohyoid and mylohyoid muscles . The posterior margin of the soft palate supports the uvula, a dangling process that helps prevent food from entering the pharynx prematurely. On either side of the uvula are two pairs of muscular pharyngeal arches. Salivary Glands Three pairs of salivary glands secrete into the oral cavity. Each pair has a distinctive cellular organization and produces saliva, a mixture of glandular secretions, with slightly different properties. The large parotid salivary glands lie inferior to the zygomatic arch deep to the skin covering the lateral and posterior surface of the mandible. The sublingual salivary glands are covered by the mucous membrane of the floor of the mouth. These glands produce a mucous secretion that acts as a buffer and lubricant. The submandibular salivary glands are on the floor of the mouth along the inner surfaces of the mandible within a depression called the mandibular groove. The Teeth The tongues movements are vital to passing food across the opposing surfaces or occlusal surfaces of the teeth. These surfaces perform chewing (or mastication ) of food. Mastication breaks down tough connective tissues in meat and the plant fibers in vegetable matter, and it helps saturate the materials with salivary secretions and enzymes. The bulk of each tooth consists of a mineralized matrix similar to that of bone. This material is called dentin. The pulp cavity receives blood vessels and nerves through an opening in the root canal, a narrow tunnel located at the root of the tooth, called apical foramen. The root of each tooth sits in a bony socket called an alveolus . Collagen fibers of the periodontal ligament extend from the dentin of the root to the bone of the alveolus, creating a strong articulation known as a gomphosis . The dentin of the root is covered by a layer of cementum that provides protection and firmly anchors the tooth to the periodontal ligament. The exposed portion of the tooth that extends past the soft tissue of the gingiva is referred to as the neck of the tooth. The neck of the tooth marks the boundary between the root and the crown. A layer of enamel covers the dentin of the crown. Enamel, which contains calcium phosphate in a crystalline form, is the hardest biologically manufactured substance. Adequate amounts of calcium, phosphates, and vitamin D during childhood are essential if the enamel coating is to be complete and resistant to decay.

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