Submandibular Glands

Overview

The submandibular glands are paired major salivary glands responsible for producing a significant portion of the saliva in the oral cavity. These glands are second in size only to the parotid glands and secrete a mixture of serous and mucous saliva. Their strategic location and ductal architecture make them essential in maintaining oral lubrication, initiating digestion, and protecting oral tissues.

Location

The submandibular glands are located in the submandibular (digastric) triangle of the neck. Specifically, they are:

• Situated beneath the floor of the mouth and inferior to the mandible

• Wrapped partially around the posterior edge of the mylohyoid muscle, dividing each gland into superficial and deep parts

• Anterior to the angle of the mandible and close to the facial artery and vein

Structure

The submandibular glands are:

• Mixed glands: Composed of both serous acini (dominant) and mucous acini

• Approximately 10–15 grams in weight

• Drained by the submandibular (Wharton’s) duct, which opens at the sublingual caruncle near the base of the tongue

• Innervated by: Parasympathetic fibers of the facial nerve (CN VII) via the chorda tympani and submandibular ganglion

• Supplied by: The facial and lingual arteries and drained via accompanying veins

Function

The submandibular glands serve multiple essential functions:

• Saliva production: Contribute approximately 65–70% of resting (unstimulated) salivary output

• Seromucous secretion: Their saliva is primarily serous (watery and enzyme-rich) with some mucous (thick and lubricating) components

• Facilitate digestion: Secrete salivary amylase (ptyalin) to begin starch digestion in the mouth

• Oral hydration: Moistens food, helps with swallowing, and protects mucosal surfaces

Physiological Role(s)

The submandibular glands play a continuous and responsive role in:

• Basal and reflexive secretion: Continuously secrete saliva at rest and increase output in response to taste, smell, and mastication

• Buffering capacity: Secrete bicarbonate ions to maintain oral pH and neutralize acids

• Antimicrobial defense: Saliva contains lysozyme, lactoferrin, IgA, and other agents that inhibit bacterial growth

• Taste perception: Saliva acts as a solvent for tastants and maintains taste bud health

Clinical Significance

The submandibular glands are frequently involved in both benign and pathological conditions:

• Sialolithiasis (salivary stones): Most common in the submandibular glands due to the upward course and mucous nature of Wharton’s duct; may cause pain and swelling during meals

• Sialadenitis: Bacterial or viral infection of the gland, often secondary to obstruction; presents with tenderness, redness, and pus at the duct opening

• Ranula: A mucous cyst arising from rupture or blockage of the duct; appears as a bluish swelling in the floor of the mouth

• Neoplasms: Tumors can develop, though less common than in the parotid; often benign but may be malignant

• Surgical considerations: Submandibular gland excision may be performed for tumors or recurrent stones; care is needed to preserve the lingual nerve and marginal mandibular branch of the facial nerve

• Dry mouth (xerostomia): Dysfunction, excision, or radiation damage can reduce saliva and affect oral health and digestion

Diagnostic tools include ultrasound, sialography, CT/MRI, and fine needle aspiration (FNA) for tumor evaluation. Treatment may be conservative or surgical depending on the underlying condition.