Salivary glands are exocrine glands responsible for producing and secreting saliva into the oral cavity. Saliva aids in moistening food, digestion, lubrication, and oral hygiene. These glands are composed of serous, mucous, or mixed secretory cells that release enzymes, electrolytes, and mucus to maintain oral health and digestive function.
Location
Salivary glands are located in and around the oral cavity and are divided into major and minor glands:
- Major salivary glands
- Minor salivary glands
- Scattered throughout the lips, cheeks, palate, and throat in smaller clusters.
Anatomy
Major salivary glands
1. Parotid glands
- Location – Positioned anterior to the ears, extending over the masseter muscle and reaching below the zygomatic arch.
- Structure – Largest of the salivary glands, weighing approximately 15–30 grams each.
- Secretions – Produces serous (watery) saliva rich in amylase, which helps in starch digestion.
- Duct – Drains through the Stensen’s duct, which opens near the second upper molar in the oral cavity.
- Nerve supply – Controlled by the glossopharyngeal nerve (cranial nerve IX).
- Blood supply – Receives blood from the external carotid artery and drains via the retromandibular vein.
2. Submandibular glands
- Location – Found beneath the mandible in the submandibular triangle of the neck.
- Structure – Medium-sized glands, weighing approximately 10–15 grams each.
- Secretions – Produces mixed saliva (both serous and mucous), primarily serous.
- Duct – Drains through the Wharton’s duct, opening at the sublingual caruncles near the base of the tongue.
- Nerve supply – Innervated by the facial nerve (cranial nerve VII) via the chorda tympani.
- Blood supply – Supplied by the facial artery and lingual artery, with venous drainage via the facial vein.
3. Sublingual glands
- Location – Situated beneath the tongue in the floor of the mouth, near the mandibular symphysis.
- Structure – Smallest of the major glands, weighing approximately 2–3 grams each.
- Secretions – Produces mostly mucous saliva with some serous components for lubrication.
- Duct – Drains through multiple ducts called Rivinus ducts, with the largest duct (Bartholin’s duct) opening near the Wharton’s duct.
- Nerve supply – Innervated by the facial nerve (cranial nerve VII) via the chorda tympani.
- Blood supply – Receives blood from the lingual and facial arteries and drains via the lingual vein.
Minor salivary glands
- Location – Scattered throughout the lips, cheeks, palate, tongue, and throat.
- Structure – Small, numerous glands embedded within the oral mucosa.
- Secretions – Produce mucous saliva, contributing to moistening and lubrication of the oral cavity.
- Ducts – Open directly into the oral cavity through tiny ducts.
Types of minor salivary glands:
- Labial Glands – Located in the lips.
- Buccal Glands – Found in the cheeks.
- Palatine Glands – Present in the palate.
- Lingual Glands – Located on the tongue, near the vallate papillae and posterior region.
Histology
- Secretory units (Acini)
- Serous Acini – Produce watery, enzyme-rich saliva.
- Mucous Acini – Produce thicker, mucus-rich saliva for lubrication.
- Mixed Acini – Contain both serous and mucous cells, producing mixed saliva.
- Ductal system
- Intercalated ducts – Small ducts collecting saliva from acini.
- Striated ducts – Modify saliva by ion exchange, making it hypotonic.
- Excretory ducts – Transport saliva to the oral cavity through openings near the teeth or floor of the mouth.
Nerve and Blood supply
- Parasympathetic Innervation
- Stimulates saliva secretion.
- Controlled by the facial nerve (cranial nerve VII) and glossopharyngeal nerve (cranial nerve IX).
- Sympathetic Innervation
- Produces thicker saliva by stimulating mucous cells.
- Originates from the superior cervical ganglion.
- Blood Supply
- Parotid Gland – Supplied by branches of the external carotid artery.
- Submandibular and Sublingual Glands – Supplied by the facial and lingual arteries.
- Venous drainage occurs via the jugular veins.
Lymphatic Drainage
- Parotid Glands – Drain into the parotid lymph nodes and then to the deep cervical nodes.
- Submandibular Glands – Drain into the submandibular lymph nodes.
- Sublingual Glands – Drain into the submental lymph nodes.
Function
Saliva production and secretion
- Salivary glands produce and secrete saliva, which is essential for maintaining oral health and digestion.
- Saliva is secreted through ducts into the oral cavity to keep the mouth moist and functional.
Digestion
- Enzymatic breakdown – Saliva contains amylase (ptyalin), which begins the digestion of starches into maltose.
- Lipid digestion – The lingual lipase enzyme secreted by glands aids in the breakdown of fats.
- Food lubrication – Mucous components in saliva lubricate food, forming a bolus for easier chewing and swallowing.
Taste perception
- Saliva dissolves food particles, allowing taste buds on the tongue to detect flavors.
- It acts as a medium for transporting taste molecules to the taste receptors.
Oral moisturization and lubrication
- Keeps the oral mucosa and tongue moist, aiding in speech, chewing, and swallowing.
- Prevents dry mouth (xerostomia) and discomfort caused by dehydration.
Protection and antimicrobial activity
- Antibacterial enzymes – Saliva contains lysozyme, lactoferrin, and IgA antibodies, which inhibit bacterial growth and prevent infections.
- Buffering action – Saliva maintains a neutral pH (6.7–7.4), protecting against acid erosion and tooth decay.
- Cleansing action – Washes away food particles and debris, reducing plaque buildup.
Wound healing and tissue repair
- Contains growth factors that promote wound healing in the oral cavity.
- Protects soft tissues and teeth by forming a protective barrier against injury and irritants.
Speech facilitation
Saliva ensures lubrication of the oral cavity, enabling smooth movement of the tongue and lips, which is essential for articulation and speech production.
Thermoregulation
Helps regulate temperature in the oral cavity, providing a cooling effect during increased metabolic activity.
Waste elimination
Acts as a minor excretory route, removing metabolic waste products like urea and uric acid.
Mineralization and tooth protection
- Saliva is rich in calcium and phosphate ions, which aid in remineralization of teeth, preventing demineralization and tooth decay.
- Fluoride present in saliva strengthens tooth enamel, enhancing cavity resistance.
Clinical significance
- Xerostomia (Dry mouth) – Reduced saliva production can result from dehydration, medications, radiation therapy, or autoimmune conditions like Sjögren’s syndrome. It leads to difficulties in chewing, swallowing, and speaking, along with an increased risk of dental caries and oral infections.
- Sialolithiasis (Salivary stones) – Formation of calcified stones in the ducts, especially in the submandibular gland, can block saliva flow, causing swelling, pain, and infection. Treatment involves hydration, massage, or surgical removal.
- Sialadenitis (Inflammation) – Bacterial or viral infections, such as mumps, can cause swelling and tenderness in salivary glands, often requiring antibiotics or antiviral treatments.
- Tumors – Both benign (pleomorphic adenoma) and malignant (mucoepidermoid carcinoma) tumors can develop in salivary glands, particularly the parotid gland. Diagnosis involves imaging and biopsy, with treatment options including surgery or radiation therapy.
- Autoimmune disorders – Conditions like Sjögren’s syndrome cause chronic inflammation, leading to gland dysfunction, dryness, and potential damage. Management focuses on symptom relief through saliva substitutes and immunosuppressive therapies.
- Cysts and Abscesses – Obstruction or infection may result in fluid-filled cysts or pus-filled abscesses, requiring drainage or surgical intervention.
- Neurological disorders – Damage to nerves controlling salivary glands, such as in Bell’s palsy, can impair saliva secretion and lead to dryness.
