Saliva And Salivary Glands

Question 1

Functions of saliva

Answer 1

Lubricant for mastication, swallowing and speech

Oral hygiene - Wash
- Immunity – Antibacterial/antiviral/antifungal
- Buffer

Oral pH needs to be maintained at about pH 7.2
- bicarbonate/carbonate buffer system for rapid neutralisation of acids

Digestive enzyme
- Aqueous solvent necessary for taste

Dysfunction associated with oral pain, infections and increased risk of dental caries

Question 2

Saliva

Answer 2

Flow rate from 0.3 to 7ml per minute

Daily secretion of 800 – 1500ml in adults from major and
minor glands.

pH ranges from 6.2 to 7.4

Serous secretion – α amylase – starch digestion

Mucus secretion – mucins for lubrication of mucosal surfaces

Parotid gland = serous
Submandibular and sublingual both mucous and serous
Minor glands mainly mucous

Question 3

Factors affecting the composition and amount of saliva produced

Answer 3

Flow rate
Circadian rhythm
Type and size of gland
Duration and type of stimulus
Diet
Drugs
Age
Gender

Question 4

Saliva- Secretion of proteins and glycoproteins in a buffered electrolyte solution

Answer 4

Major contributor to oral health
Lubrication – mucous coat
Mechanical cleaning – flow
Buffering salts – neutralise acid
Remineralisation – Ca 2+ and PO43-
Defensive and digestive function - proteins

Question 5

Defence provided by

Answer 5

A)The mucosa - physical barrier

b) Palatine tonsils – lymphocyte subsets + dendritic
cells – immune surveillance and resistance to infection

c) Salivary glands – saliva washes away food particles bacteria or viruses might use for metabolic support

Question 6

Immunity

Answer 6

Salivary glands are surrounded by lymphatic system
– linked to thoracic duct and blood

Broad range of functional immune cells

Oral mucosa and glands have high blood flow rate

Question 7

Salivary Glands

Answer 7

Submandibular, sublingual and minor glands are
continuously active

Parotid – no measurable unstimulated secretion but becomes main source of saliva when stimulated (stimulation occurs before putting food into the mouth)

Unstimulated saliva is dominated by SMG components

Stimulated has composition resembling parotid secretion

Whole saliva = salivary gland secretions, blood, oral tissues,
microorganisms and food remnants

Question 8

What conditions are being tested for by using saliva tests?

Answer 8

Cystic fibrosis, TB,

Question 9

Structure of the salivary glands

Answer 9

Composed of two morphologically and
distinct epithelial tissue
– acinar cells around
– ducts - collect to form large
duct entering the mouth

Question 10

Why is the salivary gland equipped with channels and transporters in the apical and basolateral membrane?

Answer 10

Enable transport of fluid and electrolytes
I.e just like any other secretory or reabsorbing epithelia

Question 11

Two types of acini

Acini- a small saclike cavity in a gland, surrounded by secretory cells

Answer 11

Serous acini

Mucous acinus

Question 12

Serous acini

Answer 12

Dark stainingNucleus in basal thirdSmall central duct
Secrete water + α amylase

Question 13

Mucous acinus

Answer 13

Pale staining - ‘foamy’Nucleus at base
Large central duct
Secrete mucous (water + glycoproteins)

Question 14

Intralobular ducts and main excretory duct

Answer 14

Intralobular ducts divided into intercalated and striated

Question 15

Intercalated

Answer 15

short narrow duct segments with cuboidal cells that connect acini to larger striated ducts

Question 16

Striated ducts

Answer 16

striated like a thick lawn. Major site for reabsorption of NaCl

Appear striated at basal end

Basal membrane highly folded into microvilli for active transport of HCO3 against concentration gradient

Microvilli filled with mitochondria for energy to facilitate active transport

Question 17

The ducts are not just a plumbing system

Answer 17

Primary saliva – NaCl rich isotonic plasma-like fluid secreted by acini.

Electrolyte composition is modified in duct system.

Ducts secrete K+ and HCO3- and reabsorb Na+ and Cl-.

Epithelium of duct doesn’t allow any water movement so final saliva becomes hypotonic.

Question 18

2 general pathways for protein secretion:

Answer 18

Slide 33

Predominant (larger arrow) leading to saliva (mucosal; across apical
membrane).
Constitutive leading mainly towards interstitium and bloodstream
(serosal; across basolateral membrane).
Entry into regulated can be saturated by overexpression of transgene
product and “overflow” can exit via constitutive into bloodstream.

Question 19

3 pairs of major salivary glands

Answer 19

Parotid- has serous acini

Submandibular- mixed and referred to as seromucous

Sublingual- mixed but more mucous acini

Question 20

Minor salivary glands

Answer 20

Make up 20% of salivary glands

Question 21

Submucosal of oral mucosa

Answer 21

Lip cheeks, hard and soft palate, tongue

Question 22

Parotid glands

Answer 22

Superficial triangular outline between Zygomatic arch, Sternocleidomastoid, Ramus of mandible +
masseter and med pterygoid

Horizontally it has a triangular outline with apex on carotid sheath
Structures passing through parotid -
External carotid artery + terminal branches

Question 23

What are the parotid glands?

Answer 23

The parotid glands are entirely serous acini with ducts interspersed

Question 24

Anatomy of submandibular glands

Answer 24

Two lobes separated by mylohyoid muscle
-Larger superficial lobe
-Smaller deep lobe in floor of mouth

Submandibular duct (Wharton’s duct) begins in superficial lobe, wraps round free posterior border of mylohyoid, runs along floor of mouth and empties into oral cavity at sublingual papillae.

Question 25

Where are the openings of the submandibular glands?

Answer 25

Openings of the ducts at sublingual papillae

Question 26

Sublingual glands

Answer 26

Variable in size with mixed acini- mainly mucous

No large duct- drains into submandibular duct and/or small ducts that pierce oral mucosa on the floor of the mouth

Question 27

Minor salivary gland- locations

Answer 27

Concentrated in the buccal labial, palatal and lingual regions.

Also found at
-superior pole of tonsils (Weber’s glands),
tonsillar pillars
-base of the tongue (von Ebner’s glands - underlying circumvallate papillae).

Question 28

All minor salivary glands are mucous except serous glands of von Ebner

Answer 28

Minor salivary glands lack a branching network of draining ducts
- each salivary unit has own simple duct

Question 29

Parasympathetic and sympathetic stimulation

Answer 29

Stimulation of parasympathetic nerves causes the production of a copious flow of saliva while sympathetic stimulation selectively causes secretion of protein and glycoprotein

Question 30

Salivary gland disease and dysfunction

Answer 30

Obstructive
Inflammatory
Degenerative
Drug side effects
Cancer

Question 31

Obstruction

Answer 31

Saliva contains calcium and phosphate ions that can form salivary calculi (stones)

Most often in submandibular gland (c 80%)

Block duct at bend round mylohyoid [X] or at exit at sublingual papillae [X]

Question 32

Inflammatory

Answer 32

Infection secondary to blockage

Mumps (viral infection)
-Fever, malaise
-Swelling of glands
-Pain especially over parotid because capsule
does not allow much enlargement

Question 33

Degenerative

Answer 33

Complication of radiotherapy to head and neck for cancer treatment
Sjogren’s syndrome
Mainly post-menopausal females
Also affects lacrimal glands
Rheumatoid arthritis may also be present

Question 34

Drug side effects

Answer 34

The most common dysfunction

Question 35

Effects of salivary gland dysfunction

Answer 35

If salivary output falls to < 50% of normal flow – patient experiences xerostomia (dry mouth)

Low lubrication – oral function difficult

Low (natural) oral hygiene – poor pH control
Accumulation of plaque =>Rampant dental caries, gingivitis and periodontal disease
Opportunistic infections esp. fungal infections (candida = thrush)