Tongue Anatomy and Function

Tongue Anatomy

• The tongue comes from the Greek word "Glossus".
• It functions as a movable muscular organ.
• It comprises a root, body, and tip (apex).
• Key features include a curved dorsal surface and an inferior ventral surface.

Functions of the Tongue

• Mastication
• Taste
• Swallowing
• Oral Hygiene
• Speech
• Kissing
• Sensitivity
• Suckling
• Defence

Tongue Structures

• Lingual Tonsil
• Sulcus Terminalis
• Dorsum/Dorsal surface
• Lateral border
• Ventral surface
• Epiglottis
• Palatine Tonsil
• Root/Base
• Body
• Lingual Papillae
• Median Lingual Sulcus
• Apex (tip)

Dorsum of the Tongue

• The dorsum divides into two sections: the anterior two thirds (oral/body) and the posterior one third (pharyngeal/base).
• The two parts are separated by the sulcus terminalis (a triangle-shaped landmark) and the foramen caecum.

Ventral Surface

• The ventral surface relates to the 'FOM and Palate'.
• Key features include Deep Lingual Veins, Plicae Fimbriate (fimbriated fold), and the Lingual Frenum.

Lateral Border

• The ridges along the border, foliate papillae, are the main features.

Lingual Papillae Types

• Filiform
• Fungiform
• Circumvallate
• Foliate
• These papillae are located on the dorsum of the tongue.

Taste Buds

• These are barrel-shaped organs comprised of 30-80 spindle-shaped cells.
• Cells go from the basement membrane to the epithelial surface of the lingual papillae.
• Fungiform, foliate, and circumvallate papillae are associated with taste buds.
• Turnover of taste bud cells happens rapidly, about every 10 days.

Types of Cells within Taste Buds

• Supporting cells, which support the taste bud and are usually located on the outer portion
• Taste cells are located in the central portion of the taste bud

Taste Cells Details

• Taste pore is an opening in the most superficial portion of the taste bud
• Superficial taste receptors contact dissolved molecules of food at the taste pore to make a taste sensation
• Sensory neuron processes in the inferior portion of the taste bud among the cells receive messages of taste sensation by receptors
• Messages are then sent through the nerve to the central nervous system; this identifies taste

Why We Have Taste (Gustation)

• Safety: Sweet, umami, or low-salt indicate nutrient-rich foods, while bitter, sour, or highly salty indicate potentially toxic or spoiling foods.
• Physiological: It starts digestion and links to the other four senses.
• Sight, smell, and the sounds of food prepare the body by increasing saliva flow and stimulating gastric juices.
• Touch allows the body to know what type of saliva is most appropriate with food in the mouth.

Taste and Saliva

• Saliva needs to be present to experience taste.
• Taste receptors in the taste bud make contact with dissolved molecules of food.

Muscles of the Tongue (General)

• Extrinsic muscles originate outside the tongue and insert into it.
• Intrinsic muscles are contained entirely within the tongue.

Extrinsic Muscles

• Genioglossus
• Hyoglossus
• Palatoglossus
• Styloglossus
• These muscles alter the location of the tongue

Genioglossus Muscle

• Origin: superior genial tubercle (inferior aspect of the mandible)
• Insertion: into the whole surface of the tongue
• Action: Pulls the tongue forward to protrude from the mouth; depresses the tongue and forms a concavity on its dorsal surface

Hyoglossus Muscle

• Origin: hyoid bone
• Insertion: the ventral side of the tongue
• Action: Depresses the tongue & assists in retraction

Palatoglossus Muscle

• Origin: small, narrow muscle arising from the aponeurosis of the soft palate; lies within the palatoglossal arch
• Insertion: side of the tongue and blends with the intrinsic muscles
• Action: lifts up the tongue and closes off the mouth from the pharynx

Styloglossus Muscle

• Origin: a short muscle originating at the styloid process
• Insertion: blends with the inferior longitudinal muscle and the hyoglossus
• Action: draws the tongue upwards and backwards

Intrinsic Muscles

• Superior Longitudinal Muscle
• Inferior Longitudinal Muscle
• Vertical Muscle
• Transverse Muscle
• These muscles change the tongue's shape.

Superior Longitudinal Muscle

• Origin: the sub mucosa of the posterior portion of the tongue
• Insertion: the apex and anterolateral margins of the tongue
• Action: Shortens the tongue; turns the tip and the sides upwards

Inferior Longitudinal Muscle

• Origin: root of the tongue and the hyoid bone
• Insertion: into the apex of the tongue
• Action: shortens the tongue and pulls the tip and sides downwards

Vertical Muscle

• Origin: root of the tongue and genioglossus muscle
• Insertion: lingual aponeurosis
• Action: flattens and broadens the tongue

Transverse Muscle

• Origin: fibers originating in the median lingual septum
• Insertion: passes laterally to insert into the side of the tongue
• Action: narrows and lengthens the tongue

Nerve Innervation

• The tongue has both a sensory and motor nerve supply

Nerve Innervation Details

• Posterior 1/3: glossopharyngeal nerve (IX) manages both sensory and taste
• Anterior 2/3: lingual nerve handles sensory, (Trigeminal V)
  • Chorda Tympani (Facial nerve VII) and Lingual nerve manage taste
• Motor supply: hypoglossal nerve (XII) with the exception of the Palatoglossus, which the Vagus nerve (X) supplies

Blood Supply

• The lingual artery (branch of the external carotid artery) reaches the tongue
• The tongue drains mainly through the lingual vein

Geographic Tongue

• Benign condition that has smooth irregular red patches and white wavy lines, which may change position.
• Caused by inflammation.
• Can avoid acidic and spicy foods to reduce soreness; otherwise no treatment
• Named due to it looking like a map, and it's appearance likened to one

Glossitis

• Inflammation causes swelling, redness, and changes in the surface texture; categorized into acute, chronic, atrophic, and median rhomboid.
• Causes include anaemia, celiac disease, trauma, and allergic reactions.

Piercings

• The Oral Health Foundation notes tongue piercings as the most popular form.
• Bearers of piercings must take note of the impact on oral hygiene and integrity of the teeth

Black Hairy Tongue

• Overgrowth of cells creats elongated papillae
• Food, bacteria, and yeast become trapped, leading to discolouration.
• Contributing factors include smoking, antibiotics, and radiotherapy.
• Cleaning the surface with a toothbrush or tongue scraper and lifestyle changes can treat it.

Squamous Cell Carcinoma (SCC)

• SCC accounts for 95% of oropharyngeal cancers.
• The most common site (40%) is the tongue, specifically the posterior lateral border or ventral surface.