Structure and Function of the Tongue, Teeth and Mouth in Dogs

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What Are the Tongue, Teeth and Mouth?

The tongue is an elongated, mobile, muscular organ. It is the chief organ responsible for taste and obtaining food. It also aids in the chewing and swallowing of food. The teeth are highly specialized structures that tear, cut and grind food into pieces small enough to swallow. Teeth also serve as weapons of offense and defense. The mouth is the entrance to the gastrointestinal tract. The mouth, teeth and tongue are collectively termed the oral cavity.

Where Are the Tongue, Teeth and Mouth Located?

  • The tongue is located on the floor of the mouth. It extends from its posterior attachment on a small bone called the basihyoid bone to its free tip at the front of the jaw.

  • The teeth are located on both sides of the mouth. Two rows of upper teeth are anchored in the maxilla bone of the face. Two rows of lower teeth are anchored in the jaw bones (mandibular bone). Each tooth has a crown, which is the part that can be seen in the mouth, and one or more roots, which are located under the gum line The roots of the teeth are anchored within bone. Dogs generally have 28 baby teeth, also referred to as deciduous teeth, and 42 adult or permanent teeth. The permanent teeth include six pairs of sharp incisor teeth, which are in the front of the mouth, surrounded by two pairs of large canine teeth. The premolar teeth are located just behind the canine teeth. The molars sit behind the premolars and are located towards the back of the mouth.

  • The mouth is located in the lower, front part of the face and is considered the entire area between the upper and lower jaws. The mouth includes the space just outside the teeth and gums, and just inside the lips and cheeks. The main part of the mouth, or oral cavity proper, is bound on the top by the hard palate and the soft palate. On the sides and front of the mouth, the teeth and lips form the major boundary. On the bottom, the tongue and adjacent tissues form the floor of the mouth.
  • What Is the General Structure of the Tongue, Teeth and Mouth?

  • The tongue is an elongated muscular organ with the top surface covered with specialized little mushroom-shaped structures called papillae. These papillae contain tiny holes or pores that lead to taste buds. The bulk of the tongue consists of muscle bundles mixed with connective (strong/tough) and adipose (fat) tissue. It has many blood vessels and bleeds profusely when lacerated. The tongue is surrounded by the openings of the ducts of the salivary glands, which pour their secretions (saliva) into the oral cavity.

  • Each tooth consists of four types of tissue: pulp, dentin, enamel and cementum. Connective tissue surrounds the root of the tooth. This tissue, called the periodontal ligament, holds the root in the bony socket in the jaw.

    Pulp is the innermost tissue of the tooth. It is the only soft tissue of the tooth and resides in the center of tooth, especially towards the root end. It consists of connective tissue, blood vessels and nerves. The blood vessels nourish the tooth, and the nerves transmit sensations of pain, coldness, or heat to the brain.

    Dentin is a hard, yellow substance that surrounds the pulp. It makes up most of a tooth and gives the tooth an inner ivory or creamy color. Dentin is harder than bone and consists mainly of mineral salts and water. It is formed by cells called odontoblasts.

    Enamel overlies the dentin on the crown of the tooth. It forms the outermost covering of the crown. It is the hardest tissue in the body. It enables a tooth to withstand the pressure placed on it during chewing. Enamel consists of mineral salts and a small amount of water. It is usually a pearly-white color.

    Cementum covers the dentin along the root of the tooth. In most cases, the cementum and enamel meet where the root ends and the crown begins. Cementum is as hard as bone, and it consists mainly of mineral salts and water.

    The root is the portion of the tooth that lies below the gum and is embedded in the alveolus or socket. Some premolar and molar teeth have more than one root. Once teeth are fully erupted in the animal, they cease growing.

  • Dogs have two sets of teeth that develop during their most active growing period. The first set of teeth, called deciduous teeth, are temporary. Deciduous teeth are fully erupted and functional early in the second month after birth. Upon approaching maturity, when the jaws have become longer and larger, the small deciduous teeth are no longer adequate. They are shed and replaced by the permanent teeth, which last through adult life. The adult teeth are larger than the deciduous teeth. As the jaws continue to grow more permanent teeth are added in back of the mouth. These posterior teeth are molars.

  • The mouth is lined with mucus membranes. The roof of the mouth is called the palate. The front portion consists of a bone covered by a membrane and is called the hard palate. The hard palate separates the mouth from the nasal passages. The soft rear part of the roof of the mouth is called the soft palate. It forms a flexible curtain between the back of the mouth (oropharynx) and the back of the nasal cavity.

  • Other structures of the mouth include both upper and lower lips and the cheeks. Numerous small glands are present in the mouth, including the sublingual salivary gland, which sits under the tongue. The ducts of the other salivary glands also open into the mouth.
  • What Are the General Functions of the Tongue, Teeth, and Mouth?

  • The tongue of the dog has numerous functions. The tongue is used mainly for guiding food and water into the mouth and throat. The tongue assists in the chewing and swallowing of food. It serves as a ladle for lapping water and other liquids into the mouth during drinking. The taste buds of the tongue are important in the detection and sense of taste. The tongue also helps reduce body temperature in the dog. Air passing back and forth over a panting tongue is cooled, and this cooling is enhanced as saliva evaporates. Dogs also use the tongue as a tool to clean reachable areas on the body, and wounds. The dog uses it tongue to groom and to stimulate urination and defecation in puppies, especially by licking the abdomen and genital areas.

  • The teeth are used to tear apart and process the food. The food is broken down into smaller pieces by the teeth. Each type of tooth serves a different function in the chewing process. There are four types of teeth. Incisors are the primary biting teeth. The canine teeth bite and tear food. The premolars shear, grind and mash food. Molars are responsible for the most rigorous chewing.

  • The mouth itself has several important functions. It manufactures and secretes saliva. Saliva lubricates the food, helps hold food together as a bolus that can be swallowed, and contains substances that begin the digestion of the food. Saliva also cleanses the tongue. The lips help to pick up food and other substances, and help to hold food stuffs within the mouth. The mouth provides an additional way for air to enter the respiratory system. Large amounts of air may enter through the mouth during periods of exercise, excitement, or when the nasal passages are blocked due to disease.
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    What Are Some Diseases of the Tongue, Teeth and Mouth?

  • Disorders of the tongue may occur as isolated conditions, or may be involved with other disorders of the mouth. When the tongue is diseased, the animal may be reluctant to eat, may show abnormal chewing movements, may drool excessively, and have a foul odor or bloody discharge from the mouth.

    Glossitis is inflammation of the tongue. It may occur alone, or be associated with a generalized inflammation of the soft tissues of the mouth (stomatitis), inflammation of the gums (gingivitis), or of the lips (cheilitis). Causes of glossitis and stomatitis in the dog include the ingestion of foreign bodies (e.g. needles, fish hooks, tacks), exposure to chemicals and caustic agents, and irritating plants. Infectious diseases, particularly bacteria, the viruses that cause upper respiratory infections (e.g. adenovirus, distemper virus), and fungal agents (e.g. candidiasis, blastomycosis) can cause inflammation and ulceration of the tongue. Glossitis and stomatitis in the dog may also occur as a component of immune-mediated diseases, metabolic diseases, nutritional disorders, poisoning with certain toxins.

    Ulcerations can develop on the tongue in association with systemic diseases such as kidney failure and certain cancers of the body. Ulcerations can also occur with a peculiar disease of dogs called eosinophilic granuloma or eosinophilic stomatitis. Collagen degeneration and the infiltration of white blood cells called eosinophils lead to ulceration and growths on the tongue and in other areas of the mouth, especially in the Siberian husky and Cavalier King Charles spaniel. The cause of this disease is not entirely understood.

    Tumors or neoplasia may also occur on the tongue. The most tumors of the tongue in dogs are malignant, and include melanomas, squamous cell carcinomas, and fibrosarcoma. Oral papillomatosis is a contagious disease of young dogs caused by the papillomavirus. The virus causes cauliflower-type warts to develop all over the surfaces of the oral cavity. Most of these warts regress over several weeks on their own.

    Trauma may also occur to the tongue. Injuries may include burns, lacerations, puncture wounds, and bite wounds.

  • A number of dental diseases occur in the dog. Such diseases may involve only the tooth, only the gums, or the supporting tissues of the teeth. Signs associated with dental disease include a foul odor to the breath (halitosis), difficulty chewing, pain upon chewing, discoloration of the teeth or gums, discharge or bleeding from the gums or mouth, and deformity of the teeth.

    Abnormal numbers of teeth and retained deciduous may occur. Brachycephalic dogs with very short, blunt faces may have fewer teeth and shorter jaws that other dogs. Retained deciduous teeth are baby teeth that fail to fall out on their own. Any baby tooth that persists beyond six months of age is considered abnormal.

    Abnormal bite may occur in dogs. If the upper and lower teeth to do line up properly, the condition is called a malocclusion. Sometimes the upper teeth hang out further in the front of the mouth than the bottom teeth, and sometimes the opposite occurs. Abnormal bites may lead to abnormal wearing of the teeth, chronic trauma to gums, and periodontal disease.

    Periodontal disease is the development of plaque or tartar on the teeth, with secondary inflammation of the gums (gingivitis) and other supporting structures (periodontitis). Dental plaque is a yellow/gray/green substance that coats the surface of the tooth. It is composed of bacteria, proteins from saliva, and various other substances. Plaque is a major problem for animals because they do not routinely brush their teeth. Untreated plaque leads to infections around the teeth and potentially the loss of affected teeth.

    Tooth root abscesses can occur in any tooth, but are usually associated with the premolar or molar teeth. They occur more often in upper teeth, than in lower teeth. They are characterized by the accumulation of pus around the root of the tooth. When upper teeth are involved swelling may occur on the face, just beneath the eye. If the abscess ruptures to the outside, a small draining hole may be seen on the face.

    Trauma to the teeth is common in some animals. Some teeth become broken or cracked. Other teeth wear down over years of continuous use. Abrasions may also occur from chewing sharp objects. Clinical signs associated with dental trauma vary, depending upon whether the pulp cavity is exposed. Exposure of the pulp cavity is often painful.

    Tumors near the teeth may develop from the supporting or surrounding tissues. An epulis is a benign growth than arises from periodontal tissue. It appears as a pink mass arising from the gums that can go so large as to cover one or more teeth. Ameloblastoma and odontoclastic tumors may also develop near the teeth.

  • The most common disorders of the mouth include stomatitis and tumors. Disorders of the salivary glands also affect the mouth. Clinical signs associated with these conditions including difficulty eating, reluctance or refusal to eat, halitosis, drooling, bleeding from the mouth, retching or gagging, pawing at the face, rubbing the face, fever and lethargy, and sometimes nasal discharge.

    Stomatitis is an inflammation of the oral mucosa (lining of the mouth) and other soft tissues of the mouth. It has many potential causes, including all the causes of glossitis outlined above. Bacterial (e.g. spirochetes), viral (e.g. canine adenovirus, canine distemper virus), and fungal infections may cause stomatitis. Some bacteria that are normal residents of the mouth may take advantage of inflammation in the mouth to create significant infections.

    Tumors of the mouth are often malignant in dogs and usually involve the soft tissues of the mouth. Tumors of the bones of the mouth are also possible, but occur less often. Examples include the malignant melanoma, squamous cell carcinoma, fibrosarcoma, and osteosarcoma.
    A ranula is a swelling that develops under the tongue from the formation of a cyst of the sublingual salivary gland. The swelling may become large and inflamed, causing the tongue to be pushed upwards or to the side. The dog may have difficulty eating, may drool or exhibit excessive licking, and may act painful when the mouth is opened or manipulated. Cysts may also develop from other salivary glands and impinge upon the structures of the mouth.
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    What Types of Diagnostic Tests Are Used to Evaluate the Tongue, Teeth, and Mouth?

    Veterinarians use a number of different tests to evaluate the tongue, teeth and mouth. A thorough oral examination using an external light source is the single most important test in evaluating structures in the oral cavity. Many times tranquilization or even anesthesia is necessary for a thorough evaluation of all of the oral structures. Oral examination is followed by a thorough physical examination in order to detect other signs of illness or organ involvement.

    Depending upon the clinical signs, the age and overall health of the dog, and the findings on oral and physical examination, other specific tests may be recommended by your veterinarian. Tests designed to evaluate disorders of the tongue, teeth and mouth include the following:

  • Swabs of the mouth may be taken for cytology (microscopic examination) and bacterial staining and culture. Tests may also be performed to detect certain viruses and fungal agents.

  • Blood samples may be submitted for a complete blood count to search for signs of infection, for a biochemistry profile to look for evidence of other organ diseases, and for certain infectious diseases such as feline leukemia virus and feline immunodeficiency virus.

  • X-rays of the skull, jaw, and teeth may be helpful. Such X-rays require that the animal be placed under general anesthesia.

  • Biopsies of abnormal tissue, masses may be required to reach a definitive diagnosis.

  • Some lesions are only diagnosed with surgical removal and exploration of the abnormal area in the mouth.
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