Anatomy of Oral Cavity: Tongue, teeth, Palate

  • The oral cavity, or mouth, is the first part of the digestive tract. It is bounded by the lips and cheeks and contains the teeth and tongue. The lips are muscular structures, formed mostly by the orbicularis oris muscle. The outer surfaces of the lips are covered by skin. The keratinized stratified epithelium of the skin becomes thin at the margin of the lips. The color from the underlying blood vessels can be seen through the thin, transparent epithelium, giving the lips a reddish-pink appearance.
  • At the internal margin of the lips, the epithelium is continuous with the moist stratified squamous epithelium of the mucosa in the oral cavity. The cheeks form the lateral walls of the oral cavity. Located within the cheeks are the buccinator muscles, which flatten the cheeks against the teeth. The lips and cheeks are important in the process of mastication, or chewing. The lips and cheeks move the food around within the oral cavity and hold the food in place while the teeth crush or tear it. The cheeks also help form words during the speech process.
Oral cavity

Oral Cavity

Tongue Anatomy and Functions

  • The tongue is a large, muscular organ that occupies most of the oral cavity. The major attachment of the tongue is in the posterior part of the oral cavity.  The anterior part of the tongue is relatively free, except for an anterior attachment to the floor of the mouth by a thin fold of tissue called the frenulum. The anterior two-thirds of the tongue are covered by papillae, some of which contain taste buds. The posterior one-third of the tongue is devoid of papillae and has only a few scattered taste buds.
  • In addition, the posterior portion does contain a large amount of lymphatic tissue, which helps form the lingual tonsil. The tongue moves food in the mouth and, in cooperation with the lips and cheeks, holds the food in place during mastication. It also plays a major role in the process of swallowing. In addition, the tongue is a major sensory organ for taste, as well as one of the major organs of speech.

Teeth Anatomy and Functions

  • There are 32 teeth in the normal adult mouth, located in the mandible and maxillae. The teeth can be divided into quadrants: right upper, left upper, right lower, and left lower. In adults, each quadrant contains one central and one lateral incisor; one canine; first and second premolars; and first, second, and third molars. The third molars are called wisdom teeth because they usually appear in the late teens or early twenties, when the person is old enough to have acquired some degree of wisdom. The teeth of adults are called permanent teeth, or secondary teeth. Most of them are replacements for the 20 primary teeth, or deciduous teeth, also called milk or baby teeth, which are lost during childhood.
Oral cavity

Deciduous teeth. Dental professionals have developed a “universal” numbering and lettering system for convenience in identifying individual teeth.

  • Each tooth consists of three regions: (1) a crown with one or more cusps (points), (2) a neck, and (3) a root. The crown is the visible portion of a tooth. The neck is the small region between the crown and the root. The root is the largest region of the tooth and anchors it in the jawbone. Within the center of the tooth is a pulp cavity, which is filled with blood vessels, nerves, and connective tissue, called pulp. 
  • The pulp cavity is surrounded by a living, cellular, calcified tissue called dentin. The dentin of the tooth crown is covered by an extremely hard, acellular substance called enamel, which protects the tooth against abrasion and acids produced by bacteria in the mouth. The surface of the dentin in the root is covered with cementum, which helps anchor the tooth in the jaw.
Oral cavity

Molar Tooth in Place in the Alveolar Bone

  • The teeth are held in place within alveoli along the alveolar processes of the mandible and maxillae. The alveolar processes are covered by dense fibrous connective tissue and moist stratified squamous epithelium, referred to as the gingiva, or gums. Periodontal ligaments secure the teeth in the alveoli by embedding into the cementum. Formation of dental caries, or tooth decay, is the result of the breakdown of enamel by acids produced by bacteria on the tooth surface.
  • Enamel is non-living and cannot repair itself. Consequently, a dental filling is necessary to prevent further damage. Periodontal disease is inflammation and degeneration of the periodontal ligaments, gingiva, and alveolar bone. This disease is the most common cause of tooth loss in adults. An infection may occur in a tooth, in the bone, or in the surrounding soft tissues. The infection may cause enlargement of the superior cervical lymph nodes. This is because all lymphatic drainage from the face goes through these nodes.

Palate and Tonsils

  • Palate and Tonsils the palate, or roof of the oral cavity, separates the oral cavity from the nasal cavity and prevents food from passing into the nasal cavity during chewing and swallowing. The palate consists of two parts. The anterior part contains bone and is called the hard palate, whereas the posterior portion consists of skeletal muscle and connective tissue and is called the soft palate. The uvula is a posterior extension of the soft palate. The tonsils are located in the lateral posterior walls of the oral cavity, in the nasopharynx, and in the posterior surface of the tongue.

Salivary Glands

  • Salivary Glands There are three major pairs of salivary glands: (1) The parotid glands, (2) The submandibular glands, and (3) The sublingual glands. A considerable number of other salivary glands are scattered throughout the oral cavity, including on the tongue. Salivary glands produce saliva. Saliva is a mixture of serous (watery) and mucous fluids and has multiple roles. The salivary glands are compound alveolar glands. They have branching ducts with clusters of alveoli, resembling grapes, at the ends of the ducts. The largest of the salivary glands, the parotid glands, are serous glands located just anterior to each ear. Parotid ducts enter the oral cavity adjacent to the second upper molars.
Oral cavity

Salivary Glands. Image Source: openstax.org

  • The submandibular glands produce more serous than mucous secretions. Each gland can be felt as a soft lump along the inferior border of the mandible. The submandibular ducts open into the oral cavity on each side of the frenulum of the tongue.
  • The sublingual glands, the smallest of the three paired salivary glands, produce primarily mucous secretions. They lie immediately below the mucous membrane in the floor of the oral cavity. Each sublingual gland has 10–12 small ducts opening onto the floor of the oral cavity.

Further Readings