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MBBS II HNNS > L31: Salivary & Nasal Secretion > Flashcards

L31: Salivary & Nasal Secretion Flashcards

1
Q

List the 3 major pairs of salivary glands and their contributions to resting salivary content in mouth? Location of duct opening?

A

Parotid gland –contributes 15-20%, Upper 2nd molar teeth

Submandibular gland –contributes 65-70%, underneath tongue

Sublingual gland –contributes 3-5%, Underneath tongue

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2
Q

List some minor salivary glands?

A

minor salivary glands in the bucca (cheek), labia (lip), lingual mucosa, soft palate, floor of mouth

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3
Q

Region of highest and lowest salivary flow?

A

Highest = Maxillary and mandibular region

Lowest = anterior maxillary (increase dental caries)

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4
Q

Define the mucus secreted by the 3 pairs of major salivary glands?

A

Parotid glands -serous, watery secretion

Submandibular glands - mixed secretion

Sublingual glands - mucous secretion

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5
Q

Describe the histology of serous gland cells?

A

Stain darkly (zymogen granules)

Round, central nuclei

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6
Q

Describe the histology of mucous gland cells?

A

Stain lightly

Flattened nuclei at peripheral against basement membrane

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7
Q

Role of myoepithelial cells in glands?

A

Contract when the gland is stimulated to secrete&raquo_space; expulsion of saliva

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8
Q

List the 2 types of ducts in the salivary gland acini and their appearance?

A

Intercalated duct: cuboidal, central, round nucleus

Striated ducts: Columnar, deep infolding of basal plasma membrane with abundant mitochondria (more ATP for reabsorption of NaCl)

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9
Q

List 5 functions of saliva?

A
  1. Hydration and lubrication of oral tissues (mucin = hydrophobic, resist dehydration and irritation)
  2. Facilitate mastication and deglutition
  3. Solubilization of food and enhancement of taste (solvent for tastants, hypotonic to allow salt taste)
  4. Initiating digestive process (amylase breaks down starch)
  5. Anti-bacterial oral hygiene and health of teeth
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10
Q

List some compounds in the saliva that protects against oral bacteria?

A
  1. HCO3- (= most important): increase pH
  2. Lactoferrin
  3. Agglutinins
  4. IgA, IgG, IgM
  5. Lysozyme
  6. Mucin (anti-viral,bacterial)
    (7. Others: peroxidase, histatins, cystatins…)
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11
Q

List the enzymes secreted in saliva?

A
  1. Amylase
  2. Lipase
  3. Lysozyme
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12
Q

List the ions in saliva used for reminineralization of teeth?

A

Ca2+

PO43-

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13
Q

Define the 2 stages in salivary secretion/ production?

A
  1. Produce primary saliva that is isotonic (rich in NaCl)
  2. Produce secondary saliva that is hypotonic by ductal cells
    * notice how this is reverse to the exocrine secretion in the pancreas*
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14
Q

Sequence of production of primary saliva under parasym. stimulation?

A

Parasym. activation (Ach) of GPCR&raquo_space; stimulate intracellular Ca2+ release:

1) i) Stimulate efflux of Cl- from apical membrane via Ca2+ - activated Cl- channel
ii) efflux of K at basolateral membrane via Ca2+- activated K channel
2) Cl- movement cause paracellular Na+ and water transport through tight junctions
3) Transcellular transport of water via aquaporin5(AQP5) on apical membrane

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15
Q

How is the intracellular Cl- concentration maintained in salivary acinar cells?

A

Cl- efflux by Ca2+- activated Cl- channel

NKCC1 continue to pump in Cl-, Na+ and K+ at basolateral membrane, with Na being the driver gradient (Na/K ATPase pump out Na+ at basolateral membrane)

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16
Q

List all the ion channels related to primary saliva secretion?

A

Ca2+- activated Cl- channel

NKCC1

Na/K ATPase

Aquaporin 5

Ca2+ - activated K channel

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17
Q

What is the net excretion and absorption of ions in the duct cells of salivary acini?

A

NaCl absorbed

K+HCO3- excreted

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18
Q

Describe the processes in NaCl reabsorption in the duct cells of salivary acini?

A

Na+ reabsorption via epithelial Na+ channels (ENaC) on the apical membrane, Na/K ATPase at basolateral membrane
@ striated/ excretory duct

Cl- reabsorption via Cl-/HCO3- exchanger at apical membrane, electrogenic Cl- channel at basolateral membrane

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19
Q

Describe the processes in K+ HCO3- excretion in the duct cells of salivary acini?

A

Basolateral Na/K ATPase cause accumulation of K in ductal cell&raquo_space; above equ. potential&raquo_space; trigger K+ efflux via K+ channel at apical membrane

Na+/HCO3- co-transporter cause entry of HCO3-, Exit at apical membrane via CL-/HCO3- exchanger

20
Q

List the 3 main modes of vesicular protein secretion from the Salivary Glands

A

1) Regulated secretion (accounts for 80-90 % secretion)
2) Constitutive secretion: simple exocytosis of soluble membrane protein
3) Transcytosis

21
Q

What is secreted in the saliva via transcytosis?

A

secretion of immunoglobulin complexes (produced by plasma cells) into the saliva

22
Q

Describe the regulated protein secretion process in salivary glands?

A

VAMP/SNAP ligand on Secretory granule surface

bind to cis- SNARE receptor complex on plasma membrane

> > stimulation of secretory granule and plasma membrane fusion
exocytosis

23
Q

Describe mechanism of transcytosis to release IgA in salivary glands?

A
  1. Dimeric IgA released by plasma cells into the interstitial fluid around salivary glands
  2. dimeric IgA bind with polymeric immunoglobulin receptor (pIgR) expressed on basolateral membrane of ductal epithelial cells
  3. IgA- plgR complex Internalization and transport to luminal surface
  4. pIgR is cleaved and secretory IgA is released into the saliva
24
Q

Define the 3 specific triggers for salivary secretion? **

A

mechanical (the act of chewing), gustatory, olfactory

> > control the secretion of saliva via the autonomic nervous system

25
Q

Compare the effects between parasym and sym. stimulation on the quality of saliva excreted?

A

Parasympathetic stimulation via cholinergic muscarinic M3 receptors&raquo_space; copious watery saliva

sympathetic stimulation via β-adrenergic receptors&raquo_space; protein-rich saliva, scanty, viscous

26
Q

Intracellular pathway for parasym. stimulation of saliva release at salivary acini?

A

Ach bind to M3 receptor

> > GPCR, PLC, IP3
Increase Ca2+ release to stimulate AQP5 and Ca2+- actiavated Cl- channel
increase Na+ and water transport paracellularly
Copious water and electrolyte secretion

+ stimulate myoepithelial cell contraction

27
Q

Intracellular pathway for sym. stimulation of saliva release at salivary acini?

A

NA&raquo_space; β-adrenoceptor

Activate G protein
» ATP, cAMP, PKA
» Mucin exocytosis via SNARE and SNAP complex
» Scanty, viscous, mucin excretion

+ stimulate myoepithelial cell contraction

28
Q

Define the parasympathetic nerves and pathways that innervate the 3 major salivary glands?

A

Superior salivatory nucleus&raquo_space; lingual nerve
» Submandibular ganglion
» postganglionic parasympathetic fibers of the facial nerve (VII)
» sublingual and submandibular + minor glands

Inferior salivatory nucleus 
>>  Glossopharyngeal nerve
>> Tympanic plexus >> mandibular nerve 
>> Otic ganlgion 
 >> Auriculo-temporal nerve
(postganglionic parasympathetic fibers of the glossopharyngeal nerve (IX))
>> Parotid gland
29
Q

Define the Sympathetic Innervation pathway to the Salivary Glands?

A

Preganglionic neurons at T1-T4 level of the intermediolateral (IML) cell column > paravertebral ganglia

> Postganglionic fibers exit the superior cervical ganglion (SCG)

> external carotid artery plexus and branches > all 3 salivary glands

30
Q

Define the 3 sensory signals and their reflexes that induce salivation?

A

Gustatory: gustatory-salivary reflex

Olfaction: olfactory-salivary reflex

Mechanical (chewing): masticatory-salivary reflex

31
Q

Nerve pathway for the gustatory- salivary reflex?

A

Taste buds: Anterior tongue = Facial nerve; Posterior tongue = glossopharyngeal nerve
» Nucleus solitary tract
» Superior and inferior salivatory nuclei at medulla

32
Q

Nerve pathway for the masticatory- salivary reflex?

A

Mechanoreceptors in oral mucosa and periodontal ligament&raquo_space; Trigeminal nerve&raquo_space; Trigeminal nucleus in pons&raquo_space; superior and inferior salivatory nuclei in medulla

33
Q

Nerve pathway for the olfactory- salivary reflex?

A

Olfactory receptors&raquo_space; Olfactory nerve&raquo_space; Medial olfactory area&raquo_space; descending cortical tracts&raquo_space; Superior and inferior salivatory nuclei in medulla

34
Q

Define the 3 different mucosa segments of the nasal cavity?

A

squamous mucosa, respiratory mucosa, and olfactory mucosa

35
Q

Histology of respiratory mucosa?

A

3 types of pseudostratified columnar cells attached onto the basal membrane:

1) Ciliated columnar cells
2) Non-ciliated goblet cells
3) Basal cells –process desmosomes for cell adhesion

36
Q

Describe the secretory film on the nasal mucosa?

A

Outer mucous layer (gel layer): Mucin + enzymes, viscous, produced by submucosal glands and goblet cells

Inner periciliary fluid layer (sol layer): watery, produced by ion transport through epithelium

37
Q

Function of nasal secretions

A

maintain hydration + acts as a physio chemical barrier

> > protect underlying epithelium from pathogens and particles

38
Q

What is the significance of the sol layer in nasal secretory film?

A

Sol layer = inner watery layer

Too thick = cilia cannot touch gel layer, cannot clear pathogens, particles

Too thin = cilia stuck in gel layer, cannot clear pathogens, particles

39
Q

Describe the ion transport in nasal secretion from the submucosal glands of nasal epithelium? remember HCl out

A

Cl- enter by NKCC channel at basolateral membrane, exit by CFTR channel at apical membrane

H+ exit apical membrane by NHE channel&raquo_space;acidic

Na+ drives ion transport: Enters via EnaC channel or NHE at apical membrane, Exit basolateral membrane via Na/K ATPase or Na/HCO3- co-transporter, drives NKCC by influx into cell

40
Q

Sensory innervation of nasal cavity?

A

Trigmeninal nerve:

Anterior = V1 (opthalmic nerve), Posterior = V2 (Maxillary nerve)

41
Q

Functions of nasal secretion?

A
  1. Mucocilary transport: removes material deposited in the nose
  2. Protection: immunological, bacteriocidal proteins in mucus
  3. Air-conditioning: warms, humidifies inspired air
  4. Olfaction: dissolve olfactants
42
Q

Pathway for increasing nasal secretion caused by irritants?

A

Irritant/ chemosensory stimulus
at nasal epithelium

> > depolarize to trigeminal nerve for sensory signal + Axonal reflex:

Substance P, calcitonin-gene related peptide (CGRP) released to peptidergic receptors on secretory gland cells

> > increase electrolyte transport, vasodilation

> > Copious secretion

43
Q

Pathway for increasing nasal secretion caused by allergic reaction?

A

Inflammatory mediators – histamine, bradykinin, prostaglandins in blood

1)&raquo_space; bind to glandular receptors in submucosal glands &raquo_space; induce electrolyte transport
2) Cause vasodilation and increase vascular permeability&raquo_space; exudation
3) Activate sensory and parasym. nerve&raquo_space; copious secretion

44
Q

Define the parasym. innervation pathway of nasal cavity epithelium?

A

Parasympathetic

Superioir salivatory nucleus
» hijack facial nerve (cranial nerve VII) initially
» Greater superficial petrosal nerve (GSPN)
» Vidian nerve through pterygopalatine canal
» synapse in the sphenopalatine/ pterygopalatine ganglion
» Ach + vasoactive intestinal polypeptide (VIP) release
» arteriolar vasodilation, sinusoidal engorgement, and glandular discharge

45
Q

Define the sym. innervation pathway of nasal cavity epithelium?

A

Interomedial cell column in T1
» Superior cervical ganglion
» Internal cartoid artery plexus
» synapse at Pterygopalatine ganglion
»Noradrenaline and neuropeptide Y(NPY) as neurotransmitters
» Stimulation = vasoconstriction and decrease secretion

46
Q

Summarize how sympathetic activation can lead to Nasal patency?

A

Balanced parasym. and sym. activation

> > Normal glandular secretion + NA/NPY release causes collapse of capacitance vessels

> > Reduced nasal crowding

> > Normal airflow

47
Q

Summarize how parasympathetic activation can lead to Nasal congestion?

A

Parasym activation + local mucosal axon response

> > VIP, Substance P, CGRP cause dilated venous capacitance vessels, neurogenic inflammation

> > Local axon reflex cause glandular hypersecretion, edema, exudation

> > Nasal congestion

MBBS II HNNS (57 decks)

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