Oral cavity and salivary glands
Oral Cavity, Tongue, Palate, Teeth, Tonsils and Salivary Glands
Mouth anatomy for FCPS Part 1: tongue development and nerves, palate muscles, teeth and their nerves, palatine tonsil, and the three salivary glands with their ducts and secretomotor pathways. Covers deviation signs, gland tumours, stones and mumps.
Tongue: development and nerves
- The sulcus terminalis separates the anterior two-thirds (first-arch lingual swellings) from the posterior third (mainly third arch, with fourth arch near the epiglottis). The foramen caecum at its apex marks where the thyroid diverticulum began.
| Function | Anterior two-thirds | Posterior third |
|---|---|---|
| General sensation | Lingual nerve (V3) | Glossopharyngeal (IX) |
| Taste | Chorda tympani (VII) | Glossopharyngeal (IX) |
| Motor | Hypoglossal (XII) for all muscles except palatoglossus | Same |
- Palatoglossus is supplied by the vagus (pharyngeal plexus). Taste from the epiglottic region travels in the vagus.
- Genioglossus protrudes the tongue; with a hypoglossal lesion the tongue deviates towards the lesion.
- Papillae: filiform (most numerous, no taste buds), fungiform, circumvallate (in front of the sulcus, many taste buds, von Ebner glands), foliate.
- Loss of taste over the anterior two-thirds with normal touch points to the chorda tympani.
Tongue: lymph and cancer
| Part | First nodes |
|---|---|
| Tip | Submental |
| Anterior two-thirds, lateral | Submandibular, then deep cervical (jugulo-omohyoid node) |
| Posterior third | Deep cervical (jugulodigastric), often both sides |
- Central lymphatics cross the midline, so tongue cancer can spread to both sides of the neck.
- Squamous carcinoma of the tongue is commonest on the lateral border (middle third) in smokers, alcohol drinkers and tobacco chewers; a non-healing oral ulcer in such a patient is cancer until proved otherwise.
Palate
- Hard palate: palatine processes of the maxillae and horizontal plates of the palatine bones; incisive foramen (nasopalatine nerve), greater palatine foramina.
- Soft palate muscles: tensor veli palatini (V3); levator veli palatini, palatoglossus, palatopharyngeus and musculus uvulae (vagus).
- Vagus lesion: soft palate fails to rise on that side and the uvula deviates away from the lesion.
- Cleft lip (with or without cleft palate) is the commonest congenital anomaly of the head and neck. Cleft lip: failed fusion of the maxillary and medial nasal prominences. Cleft palate: failed fusion of the palatine shelves.
Teeth and their nerves
- Primary teeth 20 (6 months to about 2.5 years); permanent 32 (first molar about 6 years, third molar 17–25).
- Upper teeth: anterior, middle and posterior superior alveolar nerves (V2). Lower teeth: inferior alveolar nerve (V3), which emerges as the mental nerve below the second premolar. Inferior alveolar damage numbs the lower teeth, chin and lower lip.
- Upper molar roots project into the maxillary sinus: extraction can leave an oroantral fistula.
- Trigeminal neuralgia: brief electric-shock pains triggered by chewing, talking or touching the face, normal examination; usually V2 or V3; first-line drug carbamazepine.
Palatine tonsil
- Lies in the tonsillar fossa between the palatoglossal and palatopharyngeal arches; lymphoid tissue covered by non-keratinised stratified squamous epithelium with deep crypts.
- Bed: superior constrictor, with the glossopharyngeal nerve beneath; main artery is the tonsillar branch of the facial artery; post-tonsillectomy bleeding is often from the paratonsillar (external palatine) vein.
- Drains to the jugulodigastric node just below the angle of the mandible, which enlarges with recurrent tonsillitis. Tonsillar pain is referred to the ear via IX.
Salivary glands
| Gland | Secretion | Duct | Parasympathetic pathway |
|---|---|---|---|
| Parotid | Serous | Stensen: crosses masseter, pierces buccinator, opens opposite upper second molar | Inferior salivatory nucleus, IX, tympanic nerve, lesser petrosal, otic ganglion, auriculotemporal nerve |
| Submandibular | Mixed, mainly serous | Wharton: opens on the sublingual papilla beside the frenulum | Superior salivatory nucleus, VII, chorda tympani, lingual nerve, submandibular ganglion |
| Sublingual | Mainly mucous | Many small ducts in the floor of mouth | Same as submandibular |
- The submandibular gland has a large superficial part and a small deep part that are continuous around the posterior border of mylohyoid; the deep part lies on hyoglossus.
- The lingual nerve hooks under Wharton's duct (lateral, below, then medial). In submandibular surgery, the lingual nerve is preserved by identifying it on hyoglossus where the submandibular ganglion hangs from it before dividing the duct; the marginal mandibular branch of VII and the hypoglossal nerve are also at risk.
- Stones: about 80% in the submandibular gland because saliva is more mucous and alkaline and the duct runs uphill.
- Mumps: painful bilateral parotitis; the gland swells inside the tense, unyielding parotid fascia (from the investing layer), so chewing and sour food (salivary stimulation) are very painful.
Salivary tumours
| Tumour | Key facts |
|---|---|
| Pleomorphic adenoma | Commonest salivary tumour, usually parotid; mixed epithelial and chondromyxoid stroma; incomplete capsule with finger-like projections, so enucleation leaves tumour behind and it recurs as multiple nodules; treat by superficial parotidectomy |
| Warthin tumour | Older male smokers; often bilateral; lymphoid stroma |
| Mucoepidermoid carcinoma | Commonest malignant salivary tumour |
| Adenoid cystic carcinoma | Minor glands (palate) and submandibular; cribriform "Swiss-cheese" pattern; perineural invasion causing pain and numbness |
- In general, the smaller the gland, the more likely a tumour is malignant. Facial palsy with a parotid lump suggests malignancy.
- Frey syndrome: after parotidectomy, auriculotemporal fibres regrow into skin sweat glands (gustatory sweating).
- Melkersson–Rosenthal syndrome: recurrent facial palsy, orofacial swelling, fissured tongue.
Remember The parotid is IX through the otic ganglion; the submandibular and sublingual are VII through the chorda tympani.
Exam trap Palatoglossus (vagus) and tensor veli palatini (V3) are the exceptions to the tongue and palate rules.
Exam trap The tongue deviates towards a hypoglossal lesion; the uvula deviates away from a vagus lesion.
How FCPS asks about this
- Taste from the posterior third of the tongue: glossopharyngeal nerve; anterior two-thirds: chorda tympani.
- Origin of parotid parasympathetic fibres: inferior salivatory nucleus via IX and the otic ganglion.
- Muscle around which the submandibular gland folds: mylohyoid (posterior border).
- Recurrence of a shelled-out pleomorphic adenoma: projections through an incomplete capsule.
- Palatal tumour with perineural spread: adenoid cystic carcinoma.
- Node enlarged with tonsillitis: jugulodigastric.
- Very painful parotid swelling in mumps: unyielding parotid fascia.
Test yourself on this topic
5 of the 47 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
After surgical removal of an impacted lower left third molar, a 24-year-old man has numbness and loss of taste over the left anterior two-thirds of his tongue. Sensation of the lower lip and chin is normal. Which of the following nerves has been injured?
Answer: Lingual nerve
The lingual nerve lies directly against the lingual cortical plate of the mandible next to the third molar, where it is at risk during third molar surgery. It carries general sensation from the anterior two-thirds of the tongue and, after receiving the chorda tympani, taste fibres from the same area. Normal lip and chin sensation shows the inferior alveolar nerve is intact.
Lingual nerve injury
- Lies on lingual plate at third molar
- General sensation anterior 2/3
- Carries chorda tympani taste
Remember Third molar surgery plus numb tongue: lingual nerve.
Exam trap Taste loss with lingual injury comes from chorda tympani fibres it carries.
Why the other options are wrong
- Inferior alveolar nerve Would numb the lower lip, chin and teeth.
- Glossopharyngeal nerve Serves the posterior third of the tongue.
- Hypoglossal nerve Motor only; would cause tongue deviation, not numbness.
- Long buccal nerve Supplies the cheek and buccal gum, not the tongue.
Brisk arterial bleeding comes from the lower tonsillar bed during tonsillectomy. Which artery is the main supply of the palatine tonsil?
Answer: Tonsillar artery (facial)
The principal artery of the palatine tonsil is the tonsillar branch of the facial artery, which pierces the superior constrictor to enter the lower part of the tonsil. Minor contributions come from the ascending palatine, dorsal lingual, ascending pharyngeal and lesser palatine arteries. The commonest source of bleeding after tonsillectomy, however, is the external palatine (paratonsillar) vein.
Tonsil blood supply
- Main artery: tonsillar branch of facial
- Enters the lower pole
- Common bleeding source: paratonsillar vein
Remember Facial artery feeds the tonsil.
Exam trap Venous bleeding from the paratonsillar vein is commoner than arterial bleeding.
Why the other options are wrong
- Ascending pharyngeal artery Contributes small branches only.
- Dorsal lingual artery Contributes to the lower pole only in a minor way.
- Greater palatine artery Runs in the hard palate; the lesser palatine arteries (from the descending palatine) reach the upper pole.
- Superior thyroid artery Supplies the larynx and thyroid.
A newborn has milk coming out of the nose during feeds. The lip is intact, but there is a midline cleft of the soft palate and the hard palate behind the incisive foramen. Failure of fusion of which of the following structures caused this?
Answer: Lateral palatine processes
The secondary palate, behind the incisive foramen, forms when the two lateral palatine processes (palatal shelves) of the maxillary prominences rise above the tongue and fuse with each other and with the nasal septum. Failure gives a midline cleft of the hard and soft palate with an intact lip, causing nasal regurgitation of feeds. Clefts in front of the incisive foramen involve the primary palate, and cleft lip results from failed fusion of the medial nasal and maxillary prominences.
Cleft palate
- Secondary palate from palatal shelves
- Behind the incisive foramen
- Cleft: nasal regurgitation of milk
Remember Behind incisive foramen = shelves failed to meet.
Exam trap Cleft lip and cleft palate have different embryological causes.
Why the other options are wrong
- Medial nasal and maxillary prominences This gives cleft lip.
- Primary palate and lateral palatine processes This gives an anterior cleft, in front of the incisive foramen.
- Mandibular prominences Failure gives a rare midline lower lip or jaw cleft.
- Lateral nasal and maxillary prominences These form the nasolacrimal groove, not the palate.
A boy with mumps has very painful parotid swellings, worse on chewing and with sour food. Why is the swelling so painful?
Answer: Tense, unyielding parotid fascia
In mumps the parotid glands become inflamed and swell. The parotid is enclosed by a tough capsule derived from the investing layer of deep cervical fascia, so swelling within it raises tension sharply and stretches the capsule, causing severe pain. Pain is carried by the auriculotemporal and great auricular nerves and is worse with chewing and sour food because salivary stimulation increases gland swelling. Facial nerve palsy is rare despite the nerve passing through the gland.
Painful parotitis
- Capsule from investing fascia
- Swelling in a tight capsule
- Pain via auriculotemporal, great auricular
- Worse with sour food
Remember Mumps hurts because the parotid capsule cannot stretch.
Exam trap Bilateral painful parotids in a child are mumps until shown otherwise.
Why the other options are wrong
- Compression of the facial nerve Facial palsy is rare in parotitis.
- Stone blocking the parotid duct Stones are rare in the parotid and seldom bilateral.
- Inflammation of the TMJ capsule The joint is not the source of swelling.
- Spasm of the masseter muscle Trismus is from pain, not the cause of it.
A 4-year-old with a repaired cleft palate has recurrent bilateral glue ear. Poor action of which of the following muscles best explains this?
Answer: Tensor veli palatini
The tensor veli palatini arises partly from the cartilage of the auditory tube and opens the tube during swallowing and yawning, equalising middle ear pressure. In cleft palate its fibres insert abnormally on the cleft margin instead of forming a palatal aponeurosis, so the tube does not open well. Negative middle ear pressure leads to effusion, which is why most cleft palate children have glue ear. It is the only palatal muscle supplied by the mandibular nerve.
Cleft palate and glue ear
- Tensor veli palatini opens auditory tube
- Abnormal insertion in cleft palate
- Result: middle ear effusion
- Nerve: mandibular (V3)
Remember Cleft palate child: always check the hearing.
Exam trap Levator veli palatini lifts the palate but tensor is the main tube opener.
Why the other options are wrong
- Levator veli palatini Elevates the soft palate; helps less with tube opening.
- Palatopharyngeus Narrows the oropharyngeal isthmus during swallowing.
- Musculus uvulae Shortens and lifts the uvula.
- Superior pharyngeal constrictor Constricts the pharynx; not attached to the tube.
Where this sits in the CPSP syllabus
- Paper 1: Head, neck and back, Oral cavity, tongue, palate, teeth and salivary glands
- Surgery & Allied, Paper 2: Head and neck, Oral cavity, tongue, palate, teeth and salivary glands