Salivary Glands Quiz

Salivary Glands Overview

• Salivary glands are crucial for oral and dental sciences
• They play a role in patient management
• Related topics include: embryology, saliva & salivation, xerostomia, skull, regional anatomy, and extra-oral examination

Aim & Learning Outcomes

• The aim is to understand salivary gland positioning, histology, and function
• Learning outcomes include:
  • Listing major salivary glands
  • Describing each gland's positioning, associated ducts, saliva production, and innervation
  • Describing the histological structure of a salivary gland
  • Outlining disorders affecting salivary glands
• Salivary gland formation is covered in BMS embryology of the head, face, and oral cavity lectures

Types of Salivary Glands

• Three major bilateral pairs of salivary glands exist
  • Parotid glands
  • Submandibular glands
  • Sublingual glands
• Numerous minor salivary glands also exist
• Major glands produce 90% of saliva

Parotid Glands

• Largest major salivary glands
• 100% serous saliva
• 25% of total saliva volume
• Positioned below the external auditory meatus, between the mastoid process and the posterior border of the ramus
• Parotid duct (Stensen's duct) is 5cm long, runs outside the masseter muscle parallel to, and 1cm below the zygomatic arch, piercing the buccinator muscle opening into the oral cavity via Stensen's papillae
• Innervated by the glossopharyngeal (autonomic), auriculotemporal (sensory), and facial nerves

Submandibular Glands

• Half the size of the parotid glands (walnut-shaped)
• 60-65% of total saliva volume
• Mixed saliva secretions
• Positioned between the body of the mandible and the mylohyoid muscle, in the submandibular fossa
• Wharton's duct (5cm long) opens under the anterior part of the tongue, lateral to the lingual fraenum at the sublingual caruncle
• Innervated by the chorda tympani and lingual branch of the inferior dental nerve

Sublingual Glands

• Smallest major salivary glands (almond-sized)
• 5-10% of total saliva volume
• 60% mucous saliva
• Positioned in the floor of the mouth, in the sublingual fossa
• Bartholin's duct (10-20 smaller Rivinus ducts) opens along the sublingual fold
• Same nerve innervation as the submandibular glands

Minor Salivary Glands

• Produce mixed saliva, predominantly mucous
• Produce lots of salivary proteins
• Account for >10% of total saliva volume
• Named based on their location, e.g., buccal or labial salivary glands

Salivary Gland Structure

• Epithelium lines the ducts producing saliva
• Connective tissue surrounds the epithelium (protecting and supporting the gland) which is divided into
  • Capsule (surrounding the entire outer portion)
  • Septum (dividing the inner portion into lobes and smaller lobules), carrying nerve and blood supply to cells

Adenomeres and Acini

• Adenomeres are the working parts of a salivary gland, surrounded by connective tissue
• Acini are secretory units (made of secretory cells)
• Acini are categorised as
  • Serous acini (produce watery serous saliva), important for lubricating food, enzymatic digestion, removing epithelial debris, and diluting food
  • Mucous acini (produce viscous mucous saliva), binding food into a bolus and protecting the oral cavity from abrasion and providing lubrication
  • Serous-mucour acini (combining both serous and mucous acini)

Myoepithelial Cells

• Located within the acinus, these cells embrace acini secretory cells
• Contractions force saliva out of the lumen and into the ducts

Acinar Fluid

• Not quite saliva yet, consists of
  • Water
  • Inorganic ions
  • Small molecules and products synthesised by cells, like mucoproteins and amylase

Ducts

• Three types of ducts
  • Intercalated duct (lining of single layer of cuboidal epithelial cells)
  • Striated duct (lining of single layer of columnar epithelial cells with basal striations, aids in saliva modification)
  • Excratory duct (pseudostratified columnar epithelium with changes to stratified cuboidal and stratified squamous epithelium at opening), where saliva exits into the oral cavity

Blood Supply

• Supplied by the external carotid artery (facial and lingual artery branches) with vessels and nerves entering at the hilum
• Two capillary networks, for secretory end piece and ducts

Control of Salivation

• Salivary nuclei in the brain process senses like taste, smells, and thoughts, triggering neurotransmitter release for saliva production

Disorders of the Salivary Glands

• Hyposalivation (reduced saliva): caused by medications, radiotherapy, autoimmune diseases, diabetes, and salivary stones
• Obstruction: calcium deposits in ducts causing infection/inflammation or trauma causing saliva accumulation
• Irradiation: head and neck radiation can destroy secretory cells (atrophy) leading to xerostomia
• Degenerative disorders: Sjögren's syndrome (immunological disorder causing dry eyes, lachrymal apparatus changes)
  • Oral signs include mild erythema, mucosal thinning, erythema, fissuring, coating/depapillations on the tongue, traumatic erosions/ulcers, angular chelitis, and chapped lips
• Inflammation/infection: Mumps (viral infection causing parotid gland swelling) & Nicotine Stomatitis (minor salivary gland inflammation)
• Sialosis: painless swelling of parotid glands, not caused by inflammation/infection, can be a sign of underlying medical conditions like liver cirrhosis, bulimia, diabetes, pregnancy, obesity, and kidney failure
• Neoplasms (tumors): benign (Warthin's tumor) and malignant (salivary gland carcinoma)
• Functional disorders: dry mouth caused by emotional disturbances, mouth breathing, smoking, or use of certain medications

Summary

• Many conditions impacting salivary glands necessitate their inclusion in extra-oral examinations.

Additional Resources

• Provides links to journal articles, online books, YouTube videos, and slide sharing sites with further information and visualizations on the subject of salivary glands.