Oral cavity: subsites, lymph drainage and why they matter in cancer

Applied anatomy

The mouth is divided into small zones; knowing where a lesion sits tells you which neck nodes it drains to and how it is staged and treated.

Updated Nov 12, 2026

See it in 3D: Tongue · Soft palate · Sublingual gland · Lingual nerve · Submandibular gland · Mylohyoid · Genioglossus · Mandible · Gums (gingiva) · Lingual artery

Key points

Boundary: the oral cavity ends at the junction of hard and soft palate, the circumvallate papillae and the anterior tonsillar pillars; behind is the oropharynx.
Oral cavity subsites: lip mucosa, buccal mucosa, upper and lower alveolar ridges (gums), retromolar trigone, floor of mouth, hard palate and the anterior two-thirds of the tongue.
About 90% of oral cancers are squamous cell carcinoma; the lateral border of the tongue and the floor of the mouth are the highest-risk sites.
Tip of tongue, anterior floor and central lower lip drain to the submental nodes (level IA); the rest of the mouth mainly to submandibular (IB) and upper deep cervical (II, III) nodes.
Midline structures (tongue tip, floor of mouth, lower lip) drain to both sides of the neck; the tongue can skip directly to lower jugular nodes.
Anterior two-thirds of the tongue: general sensation by the lingual nerve (V3) and taste by the chorda tympani (VII); posterior third by the glossopharyngeal nerve.

What it is

The oral cavity runs from the lips to a ring formed by the junction of the hard and soft palate above, the circumvallate papillae of the tongue below and the anterior tonsillar pillars at the sides. Behind that ring is the oropharynx (soft palate, tonsils, base of tongue). The line matters because oral cavity cancer and oropharyngeal cancer are different diseases: oral cancer is mostly linked to tobacco and alcohol and treated mainly with surgery, while many oropharyngeal cancers are HPV-related. Inside the mouth, cancer staging uses subsites, and each subsite drains to predictable neck levels. Knowing this anatomy tells you where to look for nodes, why some tumours spread early and what a surgeon means by a neck dissection.

Applied anatomy

Lips and vestibule: the vestibule lies between lips or cheeks and teeth; the parotid duct opens in the cheek opposite the upper second molar.
Tongue: sulcus terminalis divides the oral (anterior two-thirds) from the pharyngeal part (base); foramen caecum at its apex marks the origin of the thyroglossal duct.
Tongue muscles: intrinsic muscles change its shape; extrinsic muscles (genioglossus, hyoglossus, styloglossus, palatoglossus) move it; all are supplied by the hypoglossal nerve except palatoglossus (vagus).
Floor of mouth: the mylohyoid muscle forms its diaphragm; above it lie the sublingual glands and the submandibular duct, which opens beside the lingual frenulum; the lingual nerve loops under the duct.
Hard palate and alveolar ridges: thin mucosa tightly bound to bone, so tumours here reach bone early.
Retromolar trigone: the small area behind the last lower molar, close to the mandible and the pterygoid muscles.

Clinical physiology

The mouth prepares the bolus (chewing, saliva) and starts the voluntary oral phase of swallowing.
Tongue movements shape vowels and many consonants, so tongue resection or hypoglossal palsy affects speech and swallowing.
Saliva from parotid, submandibular, sublingual and many minor glands lubricates, buffers acid and protects the teeth.
Taste reaches the brainstem through VII (anterior two-thirds), IX (posterior third) and X (epiglottic region).

Oral cavity subsites and their first lymph nodes

Subsite	First nodes	Why it matters
Lower lip (centre) and chin	Submental (IA), both sides	Midline lesions spread to both sides of the neck
Oral tongue (lateral border)	Submandibular (IB) and upper and middle jugular (II, III)	Most common subsite; may skip to level III or IV
Tongue tip	Submental (IA), then jugulo-omohyoid (III)	Bilateral drainage
Floor of mouth	Submental and submandibular (IA, IB), often both sides	High-risk site; early bilateral nodes
Buccal mucosa and gums	Submandibular (IB) and level II	Close to bone: early mandible or maxilla invasion
Retromolar trigone and hard palate	Submandibular (IB) and level II	Thin mucosa over bone; trismus if pterygoids involved

Clinical correlation

Oral cancer risk factors: any tobacco (smoked or chewed), alcohol (much worse together), and age over 40; lip cancer is linked to sun exposure.
Early oral cancer is often painless; a white or red patch, an ulcer with a hard, raised edge or a lump that lasts more than two weeks needs a biopsy.
Tumours of the alveolar ridge, retromolar trigone and hard palate invade bone early; trismus suggests spread to the pterygoid muscles.
Depth of invasion is part of the T stage of oral cavity cancer and predicts hidden neck metastases, which is why many patients have an elective neck dissection.
Tongue cancer may cause referred ear pain through the lingual nerve (V3), which shares its origin with the auriculotemporal nerve.
Hypoglossal palsy: on protrusion the tongue deviates towards the weak side; a dental infection below the mylohyoid line spreads to the submandibular space (Ludwig angina).

Next step / Initial management

Examine every subsite with good light and gloves: pull out the tongue, look under it and at its sides, and palpate the floor of the mouth with two hands (bimanual).
Any lesion persisting more than two weeks after removing an obvious cause (sharp tooth, denture): refer as a priority, within two weeks, to ENT, maxillofacial or head and neck surgery for biopsy.
Palpate neck levels IA, IB, II and III on both sides; record the size and site of the lesion and of any node.
Staging and planning are done by the specialist team with CT or MRI of the primary and the neck; a dental assessment comes before radiotherapy.
Advise stopping tobacco and alcohol in every patient with a mouth lesion.
Floor-of-mouth swelling with fever, raised tongue, drooling or breathing difficulty: refer to the emergency department the same day (Ludwig angina).

Test yourself

Think of the answer, then tap the question to see it.

Where does the oral cavity end and the oropharynx begin?

At the junction of hard and soft palate, the circumvallate papillae of the tongue and the anterior tonsillar pillars; soft palate, tonsils and base of tongue belong to the oropharynx.

A smoker and drinker has an indurated ulcer on the lateral border of the tongue. To which neck levels should you palpate first?

Submandibular (IB) and upper and middle jugular nodes (II, III); the tongue may also skip to level IV. Refer as a priority for biopsy.

Why can a tumour of the floor of the mouth spread to both sides of the neck?

Midline structures such as the floor of the mouth, tongue tip and lower lip drain to submental and submandibular nodes on both sides.

Which nerves carry general sensation and taste from the anterior two-thirds of the tongue?

General sensation: lingual nerve (V3). Taste: chorda tympani (branch of VII), which travels with the lingual nerve.

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Educational content; it does not replace a medical assessment and is not a clinical instruction. For a real case, follow current guidelines and specialist advice.

Sources: Anatomy, Head and Neck, Oral Cavity (Mouth) (StatPearls Publishing (NCBI Bookshelf), 2023); Anatomy, Head and Neck, Tongue (StatPearls Publishing (NCBI Bookshelf), 2023); Cancer of the Oral Mucosa (StatPearls Publishing (NCBI Bookshelf), 2024); Tongue Cancer (StatPearls Publishing (NCBI Bookshelf), 2023); Oral Cancer (National Institute of Dental and Craniofacial Research (NIDCR), NIH, 2024).

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