sublingual gland

**Anatomy** - Location: floor of the mouth, superior to the mylohyoid muscle, lying in the sublingual fossa of the mandible, lateral to the genioglossus and medial to the mandible. It forms the sublingual fold (plica sublingualis) under the tongue. - Ducts: 8-20 small ducts of Rivinus (minor sublingual ducts) open along the sublingual fold. Some glands join to form Bartholin's duct (major sublingual duct), which opens with or near the submandibular (Wharton's) duct at the sublingual caruncle. - Blood supply: sublingual and submental arteries (branches of the lingual and facial arteries, respectively). - Lymphatics: submental and submandibular nodes.

**Innervation and physiology** - Parasympathetic (secretomotor): the superior salivatory nucleus → facial nerve (CN VII) → chorda tympani → joins the lingual nerve (CN V3) → synapses in the submandibular ganglion → postganglionic fibers to the sublingual and submandibular glands. Stimulation (muscarinic M3) produces abundant, watery saliva. - Sympathetic: superior cervical ganglion → plexus around the arteries; produces scant, viscous, thick saliva. - Contribution to saliva: about 5% of total saliva volume (parotid ~20-25%, submandibular ~70%, in unstimulated state). The sublingual gland secretes mixed but predominantly mucous saliva (mucin-rich, so lubricating). It is largely mucous acini with serous demilunes. - Salivary functions: lubrication, antimicrobial action (lysozyme, lactoferrin, IgA), digestion (amylase and lingual lipase come mainly from the parotid and von Ebner glands), buffering (bicarbonate), and taste facilitation.

**Clinical significance** - Ranula: a mucous extravasation or retention cyst in the floor of the mouth arising from the sublingual gland (blue, translucent swelling). A "plunging" (diving) ranula extends through the mylohyoid into the neck. Treatment: excision of the sublingual gland with the cyst, or marsupialization. - Sialolithiasis: stones are most common in the submandibular gland/Wharton's duct (~80%) because its saliva is more alkaline and mucous and the duct runs upward against gravity. The sublingual gland is rarely affected (~1-2%). - Sialadenitis: bacterial infection (often Staphylococcus aureus) is more common in the parotid and submandibular glands; the sublingual gland is rarely involved. - Tumors: rare. About 90% of the sublingual gland tumors are malignant (mucoepidermoid carcinoma, adenoid cystic carcinoma). This contrasts with the parotid gland, where most tumors are benign (pleomorphic adenoma is the most common). Rule of thumb: the smaller the gland, the higher the chance of malignancy. - Sjögren syndrome: autoimmune lymphocytic destruction of salivary and lacrimal glands, causing xerostomia and keratoconjunctivitis sicca (anti-Ro/SSA, anti-La/SSB). It increases the risk of B-cell (MALT) lymphoma. Labial minor salivary gland biopsy is used for diagnosis. - Ludwig angina: bilateral cellulitis of the sublingual and submandibular spaces, usually from a mandibular molar infection; it can cause airway compromise. Treat with airway protection, IV antibiotics, and drainage. - Drugs: anticholinergics (atropine, TCAs, antihistamines) cause xerostomia; cholinergic agents (pilocarpine, cevimeline) increase salivation and treat xerostomia. - Surgical consideration: the lingual nerve and Wharton's duct are at risk during floor-of-mouth surgery.

**High-yield comparison** - Parotid: serous, CN IX (inferior salivatory nucleus → otic ganglion), Stensen's duct, pleomorphic adenoma, mumps. - Submandibular: mixed (mostly serous), CN VII, Wharton's duct, most stones. - Sublingual: mostly mucous, CN VII, Rivinus/Bartholin ducts, ranula.