Anatomy and Physiology of the Salivary Glands

1. Anatomy and Physiology of theSalivary Glands

2. 3 major glands: • • Parotid • • Submandibular • • Sublingual • • Plus many accessory glands in mucosa • • Exocrine glands that secrete directly into the oral cavity • •Important for lubricating mouth, remineralizing teeth, breaking down food • • Innervated by sensory, parasympathetic, and sympathetic fibres

3. Embryology • 6th to 8th week of gestation • Begin as oral ectodermal outpouchings into mesenchyma – point of origin is duct orifice • Parotid – first to develop & last to become encapsulated

4. Anatomy - Parotid • Largest salivary gland • Arbitrarily separated into two “lobes” by facial nerve • Compartment • Superior - Zygoma • Posterior – EAC, tail extends over SCM/mastoid • Inferior - Styloid process and muscles, carotid sheath • Anterior – Masseter and buccal fat pad

5. Anatomy - Parotid • Parotid fascia – continuation of superficial layer of deep cervical fascia • Superficial – spreads from masseter to SCM to zygoma • Deep – inferiorly forms stylomandibular membrane and connects styloid posteriorly to mandible anteriorly • Inelastic fascia, sends septations into gland preventing easy dissection

6. Anatomy - Parotid • Stensen duct – arises from anterior gland, 1.5 cm below zygoma • 4 – 6 cm long • Runs over masseter • Pierces buccinator at ant. border of masseter • Orifice is at level of 2nd maxillary molar • Buccal branch of VII parallels duct

7. Anatomy - Parotid • Arterial Supply – transverse facial artery (branch of superficial temporal) • Venous – retromandibular vein • Lymphatic: • Superficial layer below capsule – drains parotid, scalp, eyelids, EAC • Deep layer within gland – drains parotid, NP, middle ear, soft palate

8. Anatomy - Parotid

9. Anatomy - Parotid Localization of CN VII • Tragal pointer • Tympanomastoid suture • Posterior belly Digastric • Styloid process • Retrograde dissection

10. Anatomy - Parotid Histology of the Parotid Gland • compound racemose gland • large number of ducts arranged in branching system • Mostly serous alveoli with cuboidal- or columnar-lined ducts

11. Important Points about the Parotid • Largest of the salivary glands • Mostly watery serous secretion • Closely associated with facial nerve and vasculature of the face • Parotid duct opens through cheek above upper second molar • Produces most stimulated saliva

12. Anatomy - Submandibular • Second largest salivary gland • Submandibular triangle: • inferior mandible • ant/post bellies of digastric • wraps around myelohyoid to form superficial and deep lobes

13. Anatomy - Submandibular • Wharton duct; • From medial surface – courses between myelohyoid and hyoglossus to FOM • Above CN XII / Below CN V3 (lingual) • 5 cm long • Orifice is lateral to lingual frenulum

14. Anatomy - Submandibular • Arterial Supply – Facial artery • Venous Drainage – Anterior facial vein • Lymphatics: • around gland in fascia • drain to deep cervical chain

15. Anatomy - Submandibular • Histology of the submandibular gland • Mixed gland with • serous and mucous alveoli • Ducts and lobules present, but not as extensive as in parotid • Demilunes are granular serous secreting cells

16. Anatomy – Sublingual • Sublingual gland • In FOM - above myelohyoid and between mandible and geniglossus • No fascia • Drains via 10 ducts of Rivinus into FOM along the sublingual plica • Arterial – Lingual/Facial • Venous – Lingual/Facial • Lymphatics – Submandibular nodes

17. Anatomy - Minor Salivary • Minor Salivary Glands • 600 – 1,000 lining entire oral cavity, BOT, tonsillar pillars and tonsils (Weber glands) • Each gland has own simple duct • Blood supply and venous drainage by location

18. Saliva • Acts as lubricant, wetting agent, prevents irritation and protects dentition • Isotonic fluid created by acini – becomes hypotonic as moves down duct (higher flow rates  time for modification) • Active secretion of IgA, lysozyme, salivary peroxidase – innate immunity • Salivary peroxidase – glycolysis • Mucin – mucus provides moisturization of mucosa • Actively secreted by cell hyperpolarization

19. Saliva • Parotid: Serous cells only – Watery saliva • Submandibular: Mucinous and serous cells – Viscous saliva • Minor Salivary: Mixture serous and mucinous • Sublingual: Mucinous only • Salivary flow: • Unstimulated: • 69% submandibular, 26% parotid, 5% minor • rate - 0.001 – 0.2 ml/min • Stimulated: • Production reverses – 2/3 from parotid • Increases to 0.18 to 1.7 ml/min • Averages 1,000 – 1,500 ml/day

20. Function of Saliva • Moistens oral mucosa • Moistens & cools food • Medium for dissolved food • Buffer (HCO3) • Salivary peroxidase - Glycolysis • Digestion (Amylase, Lipase) • Antibacterial lysozyme, IgA,Peroxidase, FLOW) • Mineralization • Protective for dentition

21. Innervation of the Salivary Glands Main control by parasympathetic system: Submandibular and sublingual: Via chordatympani of facial nerve through submandibular ganglion Parotid: Glossopharyngeal nerve via otic ganglion Sympathetic fibres through cervical ganglion then follow blood vessels to glands

23. Factors Affecting Salivary Flow Important Factors Unimportant Factors • Degree of hydration • Body position • Exposure to light • Olfaction • Previous stimulation • Circadian rhythms • Drugs • Gender • Age (above 15 years) • Body weight • Gland size • Psychic effects • --thought/site of food • --appetite • --mental stress • Functional stimulation