The Anatomy of the Tongue and the Salivary Glands
The tongue helps you speak, taste food and move it around in your mouth, and yes, even show your obnoxious side. Salivary glands produce saliva, a clear fluid that keeps mucous membranes moist, lubricates foods while you chew, starts the digestion of starches, and helps prevent tooth decay.
When the mouth is closed, the relaxed tongue takes up most of the space inside the oral cavity. The tongue is basically muscles surrounded by a mucous membrane. It has several parts:
Root: This posterior one-third of the tongue is attached to the floor of the oral cavity.
Body: The mobile anterior two-thirds of the tongue is the body.
Apex: The apex is the tip of the tongue.
Dorsum: This part is the surface of the tongue. The terminal sulcus and the foramen cecum mark the area where the root and the body meet. It also has a midline groove that divides the tongue into left and right halves.
Inferior surface of the tongue: This part has a thin transparent membrane. A large fold of mucosa, called the frenulum, can be seen running down the midline. The ducts of the submandibular salivary glands are found at the base of the frenulum.
The anterior part of the tongue contains a large number of lingual papillae:
Vallate papillae: These papillae lie just anterior to the terminal sulcus and contain taste buds and lingual glands that secrete serous fluids.
Foliate papillae: These small folds along the sides of the tongue contain taste buds.
Filiform papillae: These papillae cover a large portion of the dorsum. They’re thread-like and sensitive to touch but do not contain taste buds.
Fungiform papillae: These mushroom-shaped papillae appear as red spots. They’re most concentrated on the apex and sides of the tongue. They also contain taste buds.
The tongue can sense five types of sensations with its papillae: sweet, salty, sour, bitter, and umami, which is a savory meaty flavor.
The muscles of the tongue
The tongue has a lot of movement due to eight pairs of muscles. They’re divided by the lingual septum. Four pairs are intrinsic, and four pairs are extrinsic. All the muscles of the tongue, except for the palatoglossus, are innervated by the hypoglossal nerve (CN XII). The palatoglossus is innervated by the pharyngeal plexus (CN X).
Following are the intrinsic muscles:
Superior longitudinal muscle: This muscle originates on the submucosal fibrous layer and the septum and inserts into the margins of the tongue and mucous membrane. It curls the tongue upward and also shortens it.
Inferior longitudinal muscle: Originating in the root of the tongue and on the hyoid bone, this muscle inserts into the apex. It curls the tongue downward and shortens it.
Transverse muscle: This muscle originates on the septum and inserts on the lateral margins of the tongue. It narrows and protrudes the tongue.
Vertical muscle: This muscle originates on the submucosal fibrous layer of the dorsum and inserts on the inferior surfaces of the borders of the tongue. It flattens and broadens the tongue.
Here are the extrinsic muscles:
Genioglossus: This fan-shaped muscle originates on the mandible and inserts onto the entire dorsum of the tongue and the hyoid bone. It protrudes the tongue and assists with other movements.
Hyoglossus: This thin muscle originates on the hyoid bone and inserts onto the inferior and lateral parts of the tongue. It depresses and shortens the tongue.
Styloglossus: This small, triangular muscle originates on the styloid process of the temporal bone and inserts onto the posterior parts of the tongue. It retrudes (pulls back) the tongue and curls its sides.
Palatoglossus: This crescent-shaped muscle originates on the palatine aponeurosis and inserts onto the posterolateral part of the tongue. It elevates the posterior part of the tongue and depresses the soft palate.
The salivary glands
The mouth has the following salivary glands:
Parotid glands: These salivary glands are the largest. They’re located between the rami of the mandible and the mastoid processes of the temporal bone. They empty saliva into the vestibule via the parotid ducts.
Sublingual glands: These glands lie in the floor of the oral cavity between the mandible and genioglossus muscle. Their sublingual ducts open into the floor of the oral cavity near the plica fimbriatae, which are lingual folds found on either side of the frenulum.
Submandibular glands: These glands are located along the body of the mandible. The submandibular duct is found between the mylohyoid and the hyoglossus muscles of the tongue and empties through small papilla on either side of the frenulum.