Salivary glands - Sub-lingual

Question 1

Anatomical position?

Answer 1

They lie on the floor of the oral cavity, situated beneath the tongue. They are bordered laterally by the mandible and medially by the genioglossus. They lie within the sublingual fossa of the medial surface of the mandible.

Both glands unite anteriorly and form a single mass through a horse configuration around the lingual frenulum. The superior aspect of this U-shape forms an elevated, elongate crest of mucous membrane called the sublingual fold.

Question 2

Anatomical relations?

Answer 2

The submandibular duct and lingual nerve pass along the medial aspect of the sublingual gland.

Question 3

Ducts of the sublingual gland?

Answer 3

Secretions drain into the oral cavity by minor sublingual ducts (or Rivinus), of which there are 8-20 excretory ducts per gland, each opening out onto the sublingual folds.

Question 4

Vasculature?

Answer 4

1) Sublingual artery (arises from the lingual artery)
2) Submental artery (arises from the facial artery)

Venous drainage correspond to the arteries.

Question 5

Innervation?

Answer 5

Parasympathetic - originates from the superior salivatory nucleus through the pre-synaptic fibres via the chorda tympani branch of CN VII. The chorda tympani unifies with the lingual branch of the mandibular nerve before synapsing onto the submandibular ganglion. Post-ganglionic innervation consists of secretomotor fibres which directly induce the gland to produce secretions, and vasodilator fibres to increase blood supply to the gland. Increased parasympathetic drive promotes saliva secretion.

Sympathetic - originates from the superior cervical ganglion, where post-synaptic vasoconstrictive fibres travel as a plexus on the internal and external carotid arteries, facial artery and finally the sublingual and submental arteries to enter each gland. Increased sympathetic drive reduces glandular bloodflow through vasoconstriction and decreases the volume of salivary secretions, resulting in a more mucus saliva.

Question 6

`Clinical relevance: Ranula

Answer 6

A ranula is a type of mucocele (mucous cyst) that occurs in the floor of the mouth inferior to the tongue. It is the most common disorder associated with the sublingual glands due to their higher mucin content in secretions compared to other salivary glands.

They can be caused by trauma to the delicate sublingual gland ducts causing them to rupture, with mucin then collecting within the connective tissues to form a cyst.

Ranulas may be small and asymptomatic and can therefore be left alone. Alternatively, they may cause pain and grow large enough to fill the mouth, causing dysphagia; an indication for sublingual gland excision. Split mucin forom the gland or ducts may collect inferiorly beneath the mylohyoid and present as swelling in the neck (a cervical ranula). Rarely, this collection can course posteriorly into the parapharyngeal space.