Chap 24.6 Oral Cavity

What are the functions of saliva? What substances are contained in saliva?

Saliva has multiple roles: It helps keep the oral cavity moist, which is needed for normal speech and for the suspension of food molecules in solution so they can be tasted; it begins the process of digestion; and it has protective functions.

Describe the stimuli that stimulate the release of saliva. What nerves are involved?

Salivary gland secretion is stimulated by both the parasympathetic and the sympathetic nervous systems, but the parasympathetic system is the more important. Salivary nuclei in the brainstem increase salivary secretions by sending action potentials through parasympathetic fibers of the facial (VII) and glossopharyngeal (IX) cranial nerves in response to a variety of stimuli, such as tactile stimulation in the oral cavity or certain tastes, especially sour. Higher centers of the brain also affect salivary gland activity. Odors that trigger thoughts of food or the sensation of hunger can increase saliva secretion.

What are the hard and soft palates?

The anterior, bony part is the hard palate. The posterior, nonbony part is the soft palate, which consists of skeletal muscle and connective tissue.

Name and give the location of the three largest salivary glands. What are the other types of salivary glands called?

The largest salivary glands, the parotid (pă-rot′id; beside the ear) glands, are serous glands, which produce mostly watery saliva; they are located just anterior to the ear on each side of the head.

Describe the mastication reflex.

The mastication reflex, or chewing reflex, is integrated in the medulla oblongata and controls the basic movements of chewing. The presence of food in the mouth stimulates sensory receptors, which activate a reflex that relaxes the muscles of mastication. As the mandible is lowered, the muscles stretch and activate a reflex that causes the muscles of mastication to contract. Once the mouth is closed, the food again stimulates the muscles of mastication to relax, and the cycle repeats. Descending pathways from the cerebrum strongly influence the mastication reflex so that chewing can be consciously initiated or stopped. The rate and intensity of chewing movements can also be influenced by the cerebrum.

List the muscle of mastication and the actions they produce.

The medial and lateral pterygoids and the masseter muscles accomplish protraction and lateral and medial excursion of the jaw. The temporalis retracts the jaw. All these movements are involved in tearing, crushing, and grinding food.

mucous part

The mucous secretions of the submandibular and sublingual glands contain a large amount of mucin (mū′sin), a proteoglycan that gives a lubricating quality to the secretions of the salivary glands.

List the three parts of a tooth. What are dentin, enamel, cementum, and pulp?

The pulp cavity is surrounded by living, cellular, calcified tissue called dentin. The dentin of the tooth crown is covered by an extremely hard, nonliving, 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 a bonelike substance called cementum, which helps anchor the tooth in the jaw.

Serous part

The serous part of saliva, produced mainly by the parotid and submandibular glands, contains a digestive enzyme called salivary amylase (am′il-ās; starch-splitting enzyme), which breaks the covalent bonds between glucose molecules in starch and other polysaccharides to produce the disaccharides maltose and isomaltose

What are the functions of the lips and cheeks?

The substance of the cheek includes the buccinator muscle (see chapter 10), which flattens the cheek against the teeth, and the buccal fat pad, which rounds out the profile on the side of the face.

What are permanent and deciduous teeth? Name the types of teeth.

The teeth of the adult mouth are called permanent teeth, or secondary teeth. Most of them are replacements for deciduous (dēsid′ū-ŭs) teeth, or primary teeth, also called milk teeth, which are lost during childhood

List the functions of the tongue. Distinguish between intrinsic and extrinsic tongue muscles.List the functions of the tongue. Distinguish between intrinsic and extrinsic tongue muscles.

The tongue moves food in the mouth and, in cooperation with the lips and gums, holds the food in place during mastication. It also plays a major role in swallowing. In addition, the tongue is a major sensory organ for taste and one of the primary organs of speech.

Where is the uvula located?

The uvula (ū′vū-lă; a grape) is a posterior projection from the soft palate.

What is the difference between the vestibule and the oral cavity proper?

The vestibule (ves′ti-bool; entry) is the space between the lips or cheeks and the teeth, and the oral cavity proper lies medial to the teeth.

submandibular glands

are mixed glands with more serous than mucous acini. Each gland can be felt as a soft lump along the inferior border of the posterior half of the mandible. A submandibular duct exits each gland, passes anteriorly deep to the mucous membrane on the floor of the oral cavity, and opens into the oral cavity beside the frenulum of the tongue

Parotid Salivary Glands

are serous glands, which produce mostly watery saliva; they are located just anterior to the ear on each side of the head. Each parotid duct exits the gland on its anterior margin, crosses the lateral surface of the masseter muscle, pierces the buccinator muscle, and enters the oral cavity adjacent to the second upper molar

intrinsic muscles

largely responsible for changing the shape of the tongue, such as flattening and elevating it during drinking and swallowing.

What muscle forms the substance of the lips?

orbicularis oris (ōr-bik′ū-lā′ris ōr′is) muscle and connective tissue.

extrinsic tongue muscles p

protrude and retract the tongue, move it from side to side, and change its shape

sublingual glands

the smallest of the three large, paired salivary glands, are mixed glands containing some serous acini but consisting primarily of mucous acini. They lie immediately below the mucous membrane in the floor of the oral cavity.