Structure and functions of the tongue
The tongue has 3 functions. It is essential for speaking. It helps in pushing the food in between the teeth for chewing and then to the food pipe so that the food goes down to the stomach.
It is indispensable for perceiving the sensation of taste. We are able to enjoy variety of dishes because our tongue can detect different tastes.
The tongue is made up of muscles covered by epithelium. The movements of tongue are quite complex. It moves in so many directions while speaking and eating. Hence many muscles are required for all these movements.
A midline fibrous septum extends throughout the length of the tongue from the hyoid bone and divides the tongue into two equal halves.
The tongue has both extrinsic and intrinsic muscles. The extrinsic muscles originate from structures outside the tongue and extend into the tongue. They are paired.
Genioglossus muscle runs from the mandible to the tongue. It protrudes the tongue and also depresses the center of the tongue.
The Hyoglossus is quadrilateral in shape. It is a thin muscle and arises from the body and greater cornu of the hyoid bone. It depresses the tongue.
The hyoid bone is situated in the midline of neck between the thyroid cartilage and the mandible. It is peculiar in that it does not articulate with any other bone.
It is shaped like a horseshoe and is suspended from the styloid processes of the temporal bones by ligaments. It supports the root of the tongue. It has five parts-a body, two greater cornu (bony projections) and two lesser cornu.
The Styloglossus muscle as the name indicates arises from the styloid process of the temporal bone and is attached to the sides of the tongue. The muscles lift the sides of the tongue to form a trough. They also help in retracting the tongue.
The Palatoglossus muscle extends between the soft palate and the tongue. It elevates the back of the tongue and helps in swallowing.
The intrinsic muscles of the tongue: There are four pairs. They alter the shape of the tongue.
The superior longitudinal muscle runs along the upper surface of the tongue. It turns the tip and side of the tongue upward so that the upper surface of the tongue becomes concave.
The inferior longitudinal muscle is situated on the under surface of the tongue. It pulls the tip of the tongue downward so that the upper surface becomes convex.
The transversus muscle arises from the midline fibrous septum, passes sideward and is attached to the fibrous tissue at the sides of the tongue. It narrows and elongates the organ.
The verticalis muscle is situated at the borders of the forepart of the organ and extends from the upper surface to the lower surface. It causes the tongue to become flat and broad.
All the intrinsic muscles of the tongue are supplied by the XII cranial nerve (hypoglossal nerve) .
The upper surface is rough due to the presence of multiple small elevated structures called papillae. There are four types of papillae-filiform (thread-shaped), fungiform (shaped like mushroom), circumvallate (circular) and foliate (leaf-shaped).
Taste buds which are specialized cells responsible for appreciating different tastes are present on all the papillae except the filiform papillae.
A taste bud is shaped somewhat like a flask with a broad base and a narrow neck opening on the upper surface of the tongue. The cells have fine hair like projections.
Stimulation of these structures leads to generation of electrical impulses which are carried by the nerves to the brain which interprets these impulses as various tastes.
The under surface of the tongue is anchored to the floor of the mouth by a fold of mucous membrane called the frenulum. But for this the tongue can slip back to the throat when we lift it.
Occasionally the frenulum can be very short resulting in a condition called tongue-tie. This can interfere with normal speech and surgery may be required.
Tongue and mouth ulcers are common in all age groups. There are many causes. Occasionally they can be caused by Vitamin B complex deficiency.
Page last reviewed on 2nd January 2011
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