Note: Being NBM (nil by mouth) does not mean no oral fluid intake is allowed, as saliva is still produced and swallowed.
Anatomy
- Parotid Gland: Releases a watery serous fluid.
- Submandibular Gland: Produces a mixed secretion, predominantly seromucinous (a combination of serous and mucus fluid).
- Sublingual Gland: Also releases seromucinous fluid. There are also numerous minor salivary glands scattered throughout the oral cavity.
Saliva Production
- Approximately 1-2 liters of saliva are produced per day.
- Salivation Stimulation: Controlled by the salivary nuclei in the brainstem, through signals from the facial (VII) and glossopharyngeal (IX) nerves.
- Salivation Inhibition: Sympathetic stimulation and anticholinergic drugs (e.g., atropine) can reduce salivation, leading to dry mouth (xerostomia).
Saliva Function
- Taste and Lubrication: Helps in dissolving food for taste sensation and lubricates the food for easier swallowing.
- Speech: Aids in articulation and speech production by moistening the oral cavity.
- Oral Health: Maintains oral hygiene by preventing drying of mucosa and has antimicrobial properties.
- pH Balance: Slightly alkaline, maintaining oral pH and protecting teeth from decay.
- Prevents Tooth Decay: By washing away food particles and neutralizing acids produced by bacteria.
- Other Functions: Saliva plays a role in human interactions, such as kissing, which promotes emotional bonding.
Saliva Composition
- 99.5% Water and Mucus
- Amylase (an enzyme that starts the breakdown of starch)
- Lysozymes (antimicrobial enzymes)
- Immunoglobulins (IgA)
- Electrolytes (such as sodium, potassium, calcium, chloride)
Pathology
- Infiltration: Diseases such as Sjögren's syndrome, sarcoidosis, and others can infiltrate salivary glands, leading to dysfunction.
- Salivary Gland Tumors:
- Pleomorphic Adenoma: The most common benign salivary gland tumour, typically affecting the parotid gland. Presents as a painless mass; treatment is resection.
- Warthin's Tumor: A benign tumour often affecting the parotid gland, sometimes bilateral. Treatment is resection.
- Mucoepidermoid Carcinoma: A malignant salivary gland tumour. It can be high or low grade, often presenting with facial nerve (VII) involvement and lymphadenopathy. Resection is the treatment if feasible.
- Adenocarcinoma: Another malignant type, often with facial nerve involvement and lymphadenopathy. Resection is the treatment of choice.
- Parotid Swelling: May be associated with:
- Liver disease or alcohol abuse
- Sarcoidosis (Mikulicz syndrome when both salivary and lacrimal glands are swollen)
- Sjögren's syndrome
- Lymphoma
- Malignancy (worrying signs include facial nerve palsy on the same side)
- Parotitis: Inflammation of the parotid gland.
- Bacterial: Often due to poor oral hygiene, dehydration, or salivary duct stones. Common organisms include Staphylococcus aureus.
- Viral: Mumps is a common viral cause, often associated with orchitis (inflammation of the testes).
- Xerostomia (Dry Mouth): Caused by:
- Medications (e.g., anticholinergics, antidepressants, lithium)
- Sjögren's syndrome
- Radiation therapy
- Dehydration or renal failure
Complications: Increased risk of dental caries and oral infections such as candidiasis.
- Sialadenitis: Inflammation of the salivary glands.
- Bacterial: Common pathogens include Staphylococcus aureus and Streptococcus species.
- Viral: Often seen in viral infections like mumps.
- Sarcoidosis: Salivary gland involvement may occur in systemic sarcoidosis, known as Heerfordt's syndrome (uveoparotid fever).
- Mikulicz's Syndrome: Enlargement of both salivary and lacrimal glands, often associated with autoimmune conditions like Sjögren's or sarcoidosis.