Anatomy And Physiology Of Salivary Glands

Anatomy And Physiology Of

Salivary Glands Dr. Supreet Singh Nayyar, AFMC

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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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Anatomy 3 Pairs – Major

salivary glands

Parotid Submandibular Sublingual

Collection of salivary tissue within oral mucosa – Minor salivary glands


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


Development Of Parotid Gland

Engulfment of facial nerve – 16th- 21st wk

Functional maturation after feeding is established


Contd…

Parotid Gland Lobulated, “inverted

pyramid”, extent

Superficial, deep lobes

Parotid space

Borders - ant, post

Surfaces – superficial, superior, anteromedial, posteromedial


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


Capsule

Structures Within The Gland


• Facial nerve, division of gland

• Retromandibular vein, anterior and posterior divisions

• External carotid artery, terminal branches

Capsule – Periparotid Nodes

Mostly superficial to Facial Nerve

Part of MALT, secrete IgA

Salivary gland tissue may be present within the lymph nodes


Lymphoid Tissue In The Gland

Intraparotid Facial Nerve Stylomastoid foramen

Methods of identification during surgery

TM Sulcus PBD Tragal pointer Mastoid Retrograde Styloid process


Branching Patterns Varied, Surgically

important

Single trunk, divides into Zygomaticotemporal, Cervicomandibular

Temporal, upper / lower zygomatic, buccal

Buccal, cervical, mandibular


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


Contd…

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


Parotid duct Formed near the

anterior border

Lies on superficial surface of Masseter

Opens in the mouth at parotid papilla

Accessory Parotid tissue


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


Submandibular Salivary Gland

Surgical Anatomy

Medial surface – Mylohyoid, Hyoglossus, Lingual nerve, XII nv, Submandibular ganglion, Deep lingual vein


Superficial Lobe

Inferior surface – Digastric, Deep fascia, Platysma, Skin

Lateral surface – Submandibular fossa, Facial artery

Extends for a variable distance between Mylohyoid & Hyoglossus

Relations Superior – Lingual nerve Inferior – XII Nv, Deep lingual vein, Submandibular

duct


Deep Lobe

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


Wharton’s duct

Branches of Facial & Lingual arteries

Lymph nodes adjacent to the superficial part


Blood Supply & Lymphatic Drianage

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


Skin incision – 4 cm below Mandible

Ligation of Facial vessels above & below

Dissected away from Lingual Nerve

Lymph nodes in substance of gland


Surgery Of Submandibular Gland

Sublingual Gland Development

8th wk Epithelial buds present

in paralingual sulcus

Almond shaped

Located in anterior part of floor of mouth


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


Ducts Multiple Drain into oral cavity directly or into Submandibular

duct

Blood supply

Nerve supply


Contd…

Physiology Of Salivary Glands

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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+


Function of Salivary Glands

Lubrication and protection

Buffering and clearance

Maintenance of tooth integrity

Antibacterial activity

Taste and digestion


Function Of Saliva

Parotid Largest, serous (Compound Tubuloacinar Gland)

Submandibular and Sublingual Mixed (Compound Tubuloacinar Glands)


Structure of Salivary Gland

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


Acini

Intercalated Ducts

Striated Ducts

Interlobular Excretory Ducts

Stenson’s, Wharton’s duct


Duct System

High rates

Rate of saliva production – 1ml/min/gm

Blood flow 10 times that of equal mass of skeletal muscle


Control of Blood Flow And Metabolism

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)


Secretion Of Saliva

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


Secretion Of Water And Electrolytes

Osmotic process Transepithelial salt gradients

Four ion transport systems - luminal and basolateral membranes generate the gradient

Three mechanisms proposed – operate concurrently


Mechanisms Of Primary Fluid Secretion

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


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


Mechanism 3 Involves acinar HCO3

- secretion

3 HCO3- secreted per

ATP molecule

H+ extruded via Na+/H- exchanger

Na+, H2O follow into the lumen


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


Mechanism Of Macromolecule Secretion

Inconstant, underlying mechanisms partially understood

Produce final hypotonic solution

Influence of tubular cells more when flow rate is slow


Mechanism Of Ductal Secretion

Predominant control – PARASYMPATHETIC

Sympathetic stimulation shorter and less strong

Probable synergistic action


Neural Control Of Gland Function

Primary fluid secretion

Protein secretion

Vasodilatation

Increased metabolism and growth

Myoepithelial cell contraction

LARGE VOLUME LOW PROTEIN OUTPUT


Parasympathetic Stimulation

High protein secretion

Vasoconstriction – decreased blood flow

Myoepithelial cell contraction

LOW VOLUME HIGH PROTEIN OUTPUT


Sympathetic Stimulation

Neurotransmitters & Receptors Parasympathetic

◦ Ach binds to M3 Receptors

◦ Activation of G protein► Phospholipase C ►IP3 & DAG ► Intracellular Ca2+ release, Protein

exocytosis


Contd… Sympathetic

◦ Noradrenaline binds to α1, β1 receptors

◦ Activation of G protein ► Adenylate Cyclase

activation ►↑cAMP dependant

Protein Kinase ►protein exocytosis


Unstimulated – Submandibular

Stimulated – Parotid 2/3rd

Acidic tastes – Max stimulation

Sweet tastes – Least stimulation


Factors Affecting Salivary Flow

Psychic factors Circadian rhythm Diurnal variation Age Drugs

Tricyclic antidepressants Phenothiazines

Depression and anxiety states Dehydration, hemorrhage,


Contd…

Salivary Gland diseases Radiation sialadenitis Autoimmune sialadenitis

HIV infection

Iron overload

Sarcoidosis

Amyloidosis

Cystic fibrosis 7/13/2012www.nayyarENT.com 47

Contd…

Flow rate Source of secretion Type of stimulus Diurnal variation Diet Drugs – flow dependant components Hormones – mineralocorticoids, ovulation


Factors Affecting Composition Of Saliva

Disease states Sialadenitis Radiation damage Sjorgen’s syndrome Cystic fibrosis HTN DM Alcoholic cirrhosis Aldosteronism Chronic pancreatitis


Contd…

Valid medium, painless, non-invasive

Hormone monitoring Unconjugated steroids Proportional to free unbound plasma levels Useful in field studies Estradiol, progesterone, testosterone


Salivary Assays In Diagnosis

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


Contd…

Tc 99m pertechnitate

Scintigraphy – objective measure of its uptake, concenteration, excretion


Radioisotope Salivary Function Tests

Concentric shells of calcareous material alternating with organic material

Stasis of flow

Distribution Submandibular gland – 92% Parotid – 6% Sublingual / minor salivary glands – 2%


Sialolithiasis

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


References

Anatomy And Physiology Of Salivary Glands

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