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Anatomy And Physiology Of
Salivary Glands
Dr. Supreet Singh Nayyar, AFMC
For more topics, visit www.nayyarENT.com
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Anatomy of Parotid, Submandibular, Sublingual glands
Physiology – structure of glands, secretion of primary fluid, neuronal control, neurotransmitters
Factors affecting salivary flow & composition
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Layout
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Anatomy
3 Pairs – Major salivary glands
Parotid Submandibular Sublingual
Collection of salivary tissue within oral mucosa – Minor salivary glands
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Ectoderm of oral cavity
Solid bulb from oropharyngeal epithelium 6 weeks - parotid gland
Dichotomous branching of solid bulb, development of lumen, condensation of mesenchyme
Formation of primitive ducts
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Development Of Parotid Gland
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Engulfment of facial nerve – 16th- 21st wk
Functional maturation after feeding is established
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Contd…
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Parotid Gland Lobulated, “inverted
pyramid”, extent
Superficial, deep lobes
Parotid space
Borders - ant, post
Surfaces – superficial, superior, anteromedial, posteromedial
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Condensed deep cervical fascia, tough, inelastic surface component, thin deep layer
Stylomandibular ligament
Fibrous septa arise from capsule
Contents of fascia – superficial lymph nodes, greater auricular nerve
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Capsule
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Structures Within The Gland
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• Facial nerve, division of gland
• Retromandibular vein, anterior and posterior divisions
• External carotid artery, terminal branches
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Capsule – Periparotid Nodes
Mostly superficial to Facial Nerve
Part of MALT, secrete IgA
Salivary gland tissue may be present within the lymph nodes
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Lymphoid Tissue In The Gland
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Intraparotid Facial Nerve
Stylomastoid foramen
Methods of identification during surgery
TM Sulcus PBD Tragal pointer Mastoid Retrograde Styloid process
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Branching Patterns
Varied, Surgically important
Single trunk, divides into Zygomaticotemporal, Cervicomandibular
Temporal, upper / lower zygomatic, buccal
Buccal, cervical, mandibular
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Type1-5 ( Katz and Catalano, 1987) Type 1 (25%) – No anastomotic links Type 2 (14%) – Buccal fuses distally with Zygomatic Type 3 (44%) – Major communication between Buccal &
others Type 4 (14%) – Anastomosis between major divisions Type 5 (3%) – More than one Facial Nv trunk
Unpredictable preoperatively, to be precisely defined during surgery
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Contd…
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Autonomic Nerve Supply
Parasympathetic
Inferior salivatory nucleus
IX nerve
Lesser Petrosal nerve
Otic ganglion
Auriculotemporal nerve
PAROTID
Sympathetic Superior cervical
ganglion
Plexus around ECA
PAROTID
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Parotid duct
Formed near the anterior border
Lies on superficial surface of Masseter
Opens in the mouth at parotid papilla
Accessory Parotid tissue
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Development 6th IU wk Ectoderm in floor of primitive oral cavity Lateral to primitive tongue Development of acini – 12th wk
Large superficial, small deep lobe Located in Submandibular triangle Well defined capsule
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Submandibular Salivary Gland
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Surgical Anatomy
Medial surface – Mylohyoid, Hyoglossus, Lingual nerve, XII nv, Submandibular ganglion, Deep lingual vein
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Superficial Lobe
Inferior surface – Digastric, Deep fascia, Platysma, Skin
Lateral surface – Submandibular fossa, Facial artery
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Extends for a variable distance between Mylohyoid & Hyoglossus
Relations Superior – Lingual nerve Inferior – XII Nv, Deep lingual vein, Submandibular
duct
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Deep Lobe
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5 cm in length Middle of deep part Crosses Sublingual space Proximally – b/w Mylohyoid & Hyoglossus Distally – b/w Genioglossus & Sublingual gland Opening – on sides of frenulum of tongue Relation to Lingual nerve
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Wharton’s duct
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Branches of Facial & Lingual arteries
Lymph nodes adjacent to the superficial part
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Blood Supply & Lymphatic Drianage
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Autonomic nerve supply Parasympathetic Superior Salivary Nucleus
Nervus Intermedius
Facial Nerve
Chorda Tympani
Lingual Nerve
Submandibular Ganglion
Sympathetic Superior Cervical
Ganglion
Plexus around Facial Artery
Submandibular Ganglion
SUBMANDIBULAR GLAND
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Skin incision – 4 cm below Mandible
Ligation of Facial vessels above & below
Dissected away from Lingual Nerve
Lymph nodes in substance of gland
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Surgery Of Submandibular Gland
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Sublingual Gland
Development 8th wk Epithelial buds present
in paralingual sulcus
Almond shaped
Located in anterior part of floor of mouth
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Relations Of Sublingual Gland
Sup – Oral floor mucosa
Inf – Mylohyoid
Post – Deep part Submandibular gland
Med – Lingual nerve, Submandibular duct, Genioglossus
Lat– Med surface of lower Mandible
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Ducts Multiple Drain into oral cavity directly or into Submandibular
duct
Blood supply
Nerve supply
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Produce saliva – 1L / day (1ml/min/gm)
Contents Mucin (glycoprotein) Salivary amylase Secretory Immunoglobulins Other enzymes – DNase, RNase, lysozyme,
lactoperoxidase, lingual lipase Kallikerin Inorganic compounds – Na+, K+, HCO3
-, Ca2+
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Function of Salivary Glands
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Lubrication and protection
Buffering and clearance
Maintenance of tooth integrity
Antibacterial activity
Taste and digestion
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Function Of Saliva
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Parotid Largest, serous (Compound Tubuloacinar Gland)
Submandibular and Sublingual Mixed (Compound Tubuloacinar Glands)
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Structure of Salivary Gland
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Secretory End Pieces (Acini) Serous Acini
◦ Pyramid shaped, basal nucleus, apical secretory granules
Mucus Acini ◦ Larger, columnar cells,
basal nucleus Mixed Acini
◦ Mucus acini capped by serous cells forming Serous Demilunes
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Acini
Intercalated Ducts
Striated Ducts
Interlobular Excretory Ducts
Stenson’s, Wharton’s duct
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Duct System
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High rates
Rate of saliva production – 1ml/min/gm
Blood flow 10 times that of equal mass of skeletal muscle
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Control of Blood Flow And Metabolism
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Active transport process under neuronal control
Composition Hypotonic to plasma Tonicity more when rates of production are high( at
max rate - 70% to that of plasma) K+,HCO3
- higher than in plasma pH – acidic during resting phase, basic during active
phase(↑ HCO3- secretion)
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Secretion Of Saliva
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Acini – Primary Fluid Secretion Isotonic to plasma, electrolyte composition fairly
constant, exocrine protein
Excretory ducts – extract Na+, Cl- and add K+, HCO3
- to saliva No addition in volume More of Na+, Cl- removed than addition of K+, HCO3
-
responsible for hypotonicity
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Secretion Of Water And Electrolytes
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Osmotic process Transepithelial salt gradients
Four ion transport systems - luminal and basolateral membranes generate the gradient
Three mechanisms proposed – operate concurrently
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Mechanisms Of Primary Fluid Secretion
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Mechanism 1 Stimulation – rise in cytosolic
Ca2+
Opening of K+, Cl- channels – KCl outflow
Cl- conc in lumen ↑, Na+, H2O follow
Cl- entry sustained via Na+K+2Cl- cotransporter
6 Cl- translocated to acinar lumen per ATP hydrolysed by Na+/K+ ATPase
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Mechanism 2 Cl-/HCO3
-, Na+/H+ exchanger
KCl outflow
Cl- entry via Cl-/HCO3- exchanger
Acidification buffered by Na+/H+
exchanger
3 Cl- translocated to lumen per ATP hydrolysed
Na+ & water follow into the lumen
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Mechanism 3 Involves acinar HCO3
- secretion
3 HCO3- secreted per
ATP molecule
H+ extruded via Na+/H- exchanger
Na+, H2O follow into the lumen
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Contained in zymogen granules present in serous acinar cells, ductal cells
Upon stimulation release contents in lumen by exocytosis
Conc and rate varies with level and type of stimulation
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Mechanism Of Macromolecule Secretion
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Inconstant, underlying mechanisms partially understood
Produce final hypotonic solution
Influence of tubular cells more when flow rate is slow
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Mechanism Of Ductal Secretion
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Predominant control – PARASYMPATHETIC
Sympathetic stimulation shorter and less strong
Probable synergistic action
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Neural Control Of Gland Function
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Primary fluid secretion
Protein secretion
Vasodilatation
Increased metabolism and growth
Myoepithelial cell contraction
LARGE VOLUME LOW PROTEIN OUTPUT
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Parasympathetic Stimulation
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High protein secretion
Vasoconstriction – decreased blood flow
Myoepithelial cell contraction
LOW VOLUME HIGH PROTEIN OUTPUT
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Sympathetic Stimulation
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Neurotransmitters & Receptors
Parasympathetic
◦ Ach binds to M3 Receptors
◦ Activation of G protein► Phospholipase C ►IP3 &
DAG ► Intracellular Ca2+ release, Protein
exocytosis
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Contd… Sympathetic
◦ Noradrenaline binds to α1, β1 receptors
◦ Activation of G protein ► Adenylate Cyclase
activation ►↑cAMP dependant
Protein Kinase ►protein exocytosis
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Unstimulated – Submandibular
Stimulated – Parotid 2/3rd
Acidic tastes – Max stimulation
Sweet tastes – Least stimulation
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Factors Affecting Salivary Flow
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Psychic factors Circadian rhythm Diurnal variation Age Drugs
Tricyclic antidepressants Phenothiazines
Depression and anxiety states Dehydration, hemorrhage,
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Salivary Gland diseases
Radiation sialadenitis
Autoimmune sialadenitis
HIV infection
Iron overload
Sarcoidosis
Amyloidosis
Cystic fibrosis
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Flow rate Source of secretion Type of stimulus Diurnal variation Diet Drugs – flow dependant components Hormones – mineralocorticoids, ovulation
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Factors Affecting Composition Of Saliva
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Disease states
Sialadenitis Radiation damage Sjorgen’s syndrome Cystic fibrosis HTN DM Alcoholic cirrhosis Aldosteronism Chronic pancreatitis
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Contd…
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Valid medium, painless, non-invasive
Hormone monitoring Unconjugated steroids Proportional to free unbound plasma levels Useful in field studies Estradiol, progesterone, testosterone
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Salivary Assays In Diagnosis
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Drugs Factors – lipid solubility, protein binding, molecular
size, flow rates Constant saliva / plasma ratio not established
Microbial antigens, antibodies Hepatitis A, B, C HIV Immunisation status
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Contd…
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Tc 99m pertechnitate
Scintigraphy – objective measure of its uptake, concenteration, excretion
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Radioisotope Salivary Function Tests
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Concentric shells of calcareous material alternating with organic material
Stasis of flow
Distribution Submandibular gland – 92% Parotid – 6% Sublingual / minor salivary glands – 2%
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Sialolithiasis
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Scott-Brown’s Otolaryngology – 6th ed, Vol 1, Vol 5
Otolaryngology Head & Neck Surgery –Charles W Cummings, 4th ed, Vol 2
Skandalakis’ Surgical Anatomy Last’s Anatomy – 9th ed Physiology – Berne & Levy, 5th ed
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References
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