Mucous Membrane of the Anterior Tongue

Mucous Membrane of the Tongue

• Anterior 2/3 of the tongue contains lingual papillae
• Four types of lingual papillae: filiform, fungiform, foliate, and vallate
• Filiform papillae are conical, highly keratinised, and contain afferent nerve endings sensitive to touch
• Fungiform papillae are scattered, keratinised, and appear as red spots (vascular core)
• Vallate papillae are large, nonkeratinised, and surrounded by deep trenches, containing taste buds
• Foliate papillae are located just in front of the V of vallate papillae, clustered in two groups on either side of the tongue, and contain taste buds

Mucous Membrane of the Posterior 1/3 of the Tongue

• No lingual papillae
• Cobblestone surface due to the presence of lymphoid nodules (lingual tonsil)

Taste Buds

• Areas of specialised epithelia (specialised mucosa) where intraepithelial structures (taste buds) function for taste perception (gustation)
• Most taste buds are located on the dorsal surface of the tongue

The Muscles of the Tongue

• Intrinsic (confined) muscles permit changes in the shape of the tongue:
  • Longitudinal
  • Transvers
  • Vertical
• Extrinsic muscles of the tongue allow for movement and changes in position:
  • Styloglossus: creates a trough for swallowing, retracting the tongue
  • Hyoglossus: depresses and retracts the tongue, making the dorsum more convex
  • Palatoglossus: elevates the posterior part of the tongue
  • Genioglossus: protrudes the tongue and deviates it towards the opposite side

Nerve Supply

• Anterior 2/3 of the tongue originates from the 1st pharyngeal arch and posterior 1/3 from the 3rd pharyngeal arch
• Sensory: general sensation for anterior 2/3 is lingual (branch of CN V) and taste fibres (special innervation) derived from the facial (CN VII) nerve (Chorda tympani)
• Motor: all the muscles of the tongue are innervated by Hypoglossal (XII CN) except palatoglossus, which is pharyngeal branch of Vagus (X CN)

The Tongue - Clinical Correlates

• Gag reflex (pharyngeal reflex) involves bilateral pharyngeal muscle contraction and elevation of the soft palate
• Afferent (sensory) IX CN and efferent (motor) X CN
• Paralysis of genioglossus (forms the bulk of tongue mass) obstructs the airway with a risk of suffocation
• Protection of the airway during general anaesthesia by inserting an airway
• Any cause leading to injury of CN XII leading to atrophy of the same side of the tongue, causing the tongue to deviate to the paralysed side
• Thin mucous membrane on the inferior side of the tongue allows for quick absorption of drugs into the deep lingual veins

Salivary Glands

• Major salivary glands:
  • Parotid
  • Submandibular
  • Sublingual
• Minor salivary glands:
  • Located just under the mucosa
  • Distributed over lips, cheeks, palate, floor of mouth, and retro-molar area
  • Also appear in the upper aerodigestive tract
  • Contribute 10% of total salivary volume

Salivary Glands - Clinical Correlates

• Sialography: radiographic examination of major ducts and secretory units of the parotid and submandibular gland by injection of contrast medium for diagnosis of stricture, stone cause obstruction
• Blockage of submandibular duct by calculi (stones)
• Majority of salivary gland tumours occur in the parotid gland; most of the tumours are benign
• Parotidectomy presents surgical challenges because the facial nerve and its branches are embedded in the gland
• Superficial parotidectomy for benign or low-grade malignancy
• Radical parotidectomy for high-grade malignancy
• Viral infection of the parotid gland (mumps) causes inflammation (parotiditis); parotid gland capsule and cervical fascia limit swelling and thus cause severe pain

Gums & Teeth

• Gums (gingivae) are composed of fibrous tissue covered with mucosa
• Improper oral hygiene results in food and bacterial deposits in gum crevices, causing gum inflammation (gingivitis)
• Untreated gingivitis leads to supporting structures and alveolar bone affected, causing periodontitis (inflammation and destruction of bone and periodontium)
• Dental abscesses
• Teeth set in tooth sockets are used in mastication and assist in speech
• Decay of teeth results in dental caries (‘cavities’) eventually invading the pulp cavity, causing pulpitis and intense pain (toothache)
• Abscesses from maxillary molar teeth may extend into the maxillary air sinus, causing sinusitis

The Palate

• Consists of a bony part (hard palate) and a muscular part (soft palate)
• Hard palate consists of four layers: a bony skeleton, submucosa, lamina propria, and cover with KSSE
• Separates the oral cavity from the nasal cavity and nasopharynx
• Soft palate is composed of musculoaponeurotic tissue, attached anteriorly to the hard palate and posteriorly free mobile, bound to the tongue and pharynx by palatoglossus and palatopharyngeus MMS