Tongue
The tongue is a muscular structure in the mouth. It is strongest muscle composed of skeletal muscle, occupies the floor of the mouth.
Tongue covered by moist stratified squamous epithelium (non-keratinized tissue).
The tongue is a muscular organ in the mouth. The tongue is covered with moist, pink tissue called mucus membrane (mucosa). On mucosa tiny bumps are present called papillae that give the tongue rough texture. There are thousands of taste buds cover the surfaces of papillae. Taste buds aids to sense taste / detecting taste.
Tongue is made up of three elements; epithelium, muscles, glands, lymph nodes.
Parts of Tongue
Tongue is divided into two parts -
1. Oral part at the front
2. Pharyngeal part at the back
Structure of Tongue
Tongue is a voluntary muscular structure. The upper surface of tongue is called dorsum, and is divided by a groove called median sulcus. This divides dorsum of the tongue into symmetrical halves.
Terminal sulcus is V-shaped groove, divides the tongue into a posterior pharyngeal part and an anterior oral part. Foramen cecum of the tongue is a depression at the posterior midline of the tongue.
1. Root of Tongue
Root of the tongue is directed backward, Aattach to mandible and soft palate above and hyoid bone below.
Base of the tongue refers ventral wall of the oropharynx. It is most posterior part of organ. It has numerous lymphoid aggregates, called lingual tonsils.
2.Tip/ Apex of Tongue
Tip of tongue is most anterior pointed portion have free end and Tip or most mobile organ.
3. Body of Tongue
Body of tongue have curve upper surface. Tip of tongue is followed by body of the tongue. It has a rough dorsal (superior) surface that have taste buds and lingual papillae, and a smooth ventral (inferior) surface attached to floor of oral cavity by lingual frenulum.
Body of the tongue contains both extrinsic and intrinsic muscles.
Intrinsic Muscles of the Tongue
Intrinsic muscles of tongue are muscles that located only in the tongue. These are -
1. Superior longitudinal muscle
2. Inferior longitudinal muscle
3. Transverse muscle
4. Vertical muscle
Extrinsic Muscles of the Tongue
Extrinsic muscles of tongue are muscle that originate from outside the tongue and then insert into the tongue. There are four pairs of extrinsic muscles-
1. Genioglossus muscle
2. Hyoglossus muscle
3. Styloglossus muscle
4. Palatoglossus muscle
The function of extrinsic muscles is reposition the tongue and the function of intrinsic muscles alter the shape of the tongue for talking and swallowing.
Papillae of Tongue
The papillae present on tongue that gives tongue rough texture, covered by number of taste buds.
Papillae are the tiny raised protrusions on the tongue that contain taste buds.
The four types of papillae are -
1. Filiform papillae (filum - thread like)
2. Fungiform papillae (mushroom- like)
3. Foliate papillae
4. Circumvallate papillae
1. Filiform papillae (thread-like)
Filiform papillae are fine, small, cone-shaped papillae covering most of the dorsum of the tongue and contain most numerous of the lingual papillae.
Filiform papillae responsible for creating rough texture of tongue and responsible for the sensation of touch and helps in chewing food.
2. Fungiform papillae (mushroom-like)
Fungiform papillae are mushroom-shaped structures located on the dorsum of the anterior two-thirds of the tongue.
3. Foliate papillae
Foliate papillae are present on each side of the tongue, it appears short vertical folds vary in size and shape.
4. Circumvallate papillae/ Vallate papillae
Circumvallate papillae is dome-shaped largest papillae on the tongue. Circumvallate papillae located shape of an inverted “V” at the back of the tongue.
Circumvallate papillae carry taste buds and also involved in gag reflex
Note - Except filiform papillae, all types of papillae contain taste buds and known asgustatory papillae.
Papillae allow to differentiate between sweet, salty, bitter, sour, and umami (savory) tastes.
Nerve Supply of Tongue
Glossopharyngeal nerve, chorda tympani nerve (branch of facial nerve) are responsible for taste sensation. Hypoglossal nerve responsible for tongue muscle movement (intrinsic and extrinsic muscle).
Trigeminal nerve is responsible for sensations of pain, touch, temperature.
Function of Tongue
1. Mechanical digestion
2. Mastification; helps in chewing
3. Deglutition; helps in swallowing
4. Secrete lingual lipase enzyme; aids in food digestion
6. Taste; transmit taste signal to brain, helps in sensing taste
7. Sensitive tactile organ; connected with sense of touch
8. Sensory receptors
9. Speech; facilitates speech
11. Lingual fernulum; limit the backward movement of tongue
12. Extrinsic muscle; move food within mouth and make round mass
Intrinsic muscle; responsible for changing in shape of tongue during drinking and swallowing and assist in swallowing.
(Both air and food pass through the pharynx. The air enters the larynx, and food enters the oesophagus).
13 Secretion; secretes mucous and serous fluid which keeps the mouth moist
14. Salivary Glands; sublingual gland
Sublingual gland opens by ducts of Rivinus on the floor of mouth by sides of frenulum of tongue.
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