Oral Histology - Salivary Glands

Protective function of saliva

- lubricant via glycoprotein

- barrier against noxious stimuli; microbial toxins and minor traumas

- washing non-adherent and acellular debris

- formation of salivary pellicle

- saliva coats all surfaces with mucin-rich secretions providing protective diffusion barrier against mechanical, thermal, chemical and microbial damage

salivary pellicle

- thin

- acellular

- organic film that forms on any type of surface upon exposure to saliva

saliva is a barrier against ______ stimuli, _______ toxins, and minor ______

noxious, microbial, traumas

saliva coats all surfaces with _____-rich secretions providing protective _________ barrier against _________, ______, _______, and microbial damage

mucin, diffusion, mechanical, thermal, chemical

buffering of saliva is via

phosphate ions and bicarbonate

buffering bacteria require specific ____ conditions; plaque microorganisms produce ______ from sugars

pH, acids

salivary pellicle is a ______________ film that forms on teeth and is pivotal in many physiological processes of the mouth

proteinaceous

Salivary pellicles protect teeth against tooth _____________ by dietary acids

demineralization

the presence of the salivary pellicle is fundamental for oral health; its absence from the mouth shows an increase in the risk of (3):

caries, gingivitis, periodontitis

digestive function of saliva

- amylase (starch) and lipase (fat) breakdown

- helps to form the food bolus

antimicrobial function of saliva

- lysozyme

- lactoferrin

- IgA

lysozyme

hydrolyzes cell walls of some bacteria

lactoferrin

binds free iron and deprives bacteria of essential element

IgA

agglutinates microorganisms

saliva functions in antiviral function via (2)

mucins, cystatins

saliva has an antifungal function via

histatins

saliva helps maintain tooth integrity via

calcium and phosphate ions - ionic exchange with the tooth surface and remineralization

saliva helps with taste by

- solubilizing food substances that can be sensed by receptors

- trophic effect on receptors

saliva helps prevent caries via

proline rich proteins that induce enamel mineralization

composition of saliva

- 99.5% water

- 0.2% inorganic

- 0.3% organic

the organic constituents of saliva

- enzymes (-ase)

- immunoglobulins

- mucous glycoproteins

- traces of albumin

- polypeptides

the pH of saliva is around ____-____

6.7-7.5

parotid saliva varies over a (lesser/greater) range than the average pH of saliva

greater

the pH of saliva depends on the ___________ concentration

bicarbonate

initially, saliva is _______ as is formed in the acini, but becomes __________ as it travels through the duct network and enhances taste

isotonic, hypotonic

the viscosity of saliva is _____________; it exhibits different viscosities at different rates of shear and has __________ properties

non-newtonian, visco-elastic

viscous behavior changes with time after secretion because of its non-newtonian properties and ______________ degradation of mucous glycoproteins by bacterial enzymes

post-secretory

gases found in saliva include

- oxygen

- CO2

- nitrogen

inorganic substances in saliva include

- sodium

- calcium

- potassium

- bromide

- chloride

- fluoride

- bicarbonate

- phosphate

enzymes found in saliva include

- amylase (ptyalin)

- lysozyme

- lingual lipase

- maltase

- phosphatase

- carbonic anhydrase

- kallikrein

other organic substances found in saliva include

- mucin

- albumin

- proline-rich proteins

- lactoferrin

- IgA

- blood group antigens

- free amino acids

- non protein nitrogenous substances like urea, uric acid, creatinine, xanthine, hypoxanthine

glucose is present in saliva during

diabetes mellitus

types of glands include

- simple alveolar (acinar)

- simple branched alveolar

- compound alveolar (acinar)

- simple tubular

- simple coiled tubular

- simple branched tubular

- compound tubular

- compound tubuloalveolar

simple alveolar/acinar glands

- not in adults

- stage in development of simple branched glands

simple branched alveolar glands

sebaceous (oil) glands

simple tubular glands

intestinal glands

simple coiled tubular glands

merocrine sweat glands

simple branched tubular glands

- gastric glands

- mucous glands of esophagus, tongue, duodenum

compound alveolar/acinar

mammary glands

compound tubuloalveolar glands

- salivary glands

- glands of respiratory passages and pancreas

compound tubular glands

- mucous glands in mouth

- bulbourethral glands in male reproductive system

- in testes (seminiferous tubules)

at around the 7-8th month in utero, __________ cells begin to develop around the ductal system

secretory

secretory cells differentiate from a separate pool of cells than do the _______ cells, giving each type of cell unique characteristics

ductal

secretory cells are classified as either

mucous cells or serous cells

mucous cells

- more thick, viscous secretion

- show clear cytoplasm because it mostly contains mucopolysaccharides which do not retain common dyes (lightly stained)

- mucigen droplets

- secretory endpieces composed of these have tubular configuration

- in cross section, tubules appear round with these cells surrounding a large, central lumen

- nucleus is flat and peripheral

- protect and lubricate

- most prominent feature is the accumulation in the apical cytoplasm of large amounts of secretory product which compresses the nucleus and ER against the basal cell membrane

- large Golgi complex basal to mass of secretory granules

- ER and other organelles limited mainly to basal cytoplasm of cell

- mostly sublingual gland

mucous end pieces in major salivary glands and some minor salivary glands have serous cells associated with them in the form of _______ covering the mucous cells at the end of the tubule

demilune

the secretory material of mucous cells gives an ________ appearance to the supranuclear cytoplasm

empty

like serous cells, mucous cells are joined by

a variety of intercellular junctions

like serous cells, mucous cells lack ___________ __________ except for those covered by demilune cells

intercellular canaliculi

serous cells

- thin, watery, proteinaceous secretion

- show more dark cytoplasm due to high enzymatic content with amylases as the most abundant enzymes (enyzmatic action)

- typically spherical, 8-12 cells surrounding a small, central lumen

- central, rounded nucleus with indistinct cell boundaries

- pyramidal cells with a broad base and narrow apex

- spherical nuclei are located basally

- numerous secretory granules in which macromolecular components of saliva are stored, and present in apical cytoplasm

- zymogen granules in cyto

- parotid gland

the basal cytoplasm of serous cells contain

- numerous cisternae of RER

- converge on a large Golgi complex located just apical or lateral to the nucleus

the granules of serous cells may

- have a variable appearance

- increase in density as their content condenses, eventuall forming mature secretory granules

where do you find serous demilune

- only in the mixed gland

- crescent, half moon shaped clusters of serous cells

pure serous end piece

- less cells, lumen smaller than mucous one

- relatively central nucleus

- picks up darker pink color when staining

mucous endpiece

- more tubular

- nucleus is pushed into the basal layer

- canal/opening is much wider

- will pick up lighter shade of pink when staining

serous travels from

intercalated duct > striated duct > excretory duct

mucin end pieces only stain

dark purple; acid-Schiff stain

all salivary glands are compound

tubulo-alveolar glands

structure of salivary gland

- consists of series of branched ducts terminating in spherical or tubular secretory end pieces/acini

- main excretory duct that empties into the oral cavity divides into smaller interlobar and interlobular ducts that enter lobes and lobules of the gland

- predom intralobular ductal component is striated duct, playing major role in modification of primary saliva produced by secretory end pieces

- connecting striated ducts to secretory end pieces are intercalated ducts, which branch 1 or 2 times before joining individual end pieces

- lumen of end piece is continuous with intercalated duct

major salivary glands make up ___% of total secretion

90

minor salivary glands make up ___% of total secretion

10

3 major salivary glands

- parotid (25%)

- submandibular (60%)

- sublingual (5%)

minor salivary glands

- glossopalatine

- labial, lingual, palatal

- mucous glands in the cheek that spread in the oral cavity except at the gingiva and anterior part of the hard palate

parotid

- largest encapsulated salivary gland

- pure serous in adults

- no serous demilunes

- 25% salivary volume

- CN VII (Facial) gives rise to 5 terminal branches within this gland

- main duct is Stenson's duct

- may be able to see the orifice in your own mouth in the cheek

submandibular

- second largest major salivary gland in size

- provides most of the total salivary volume (60%)

- mixed but predominately serous

- main duct is Wharton's duct, which opens at the sublingual caruncle on floor of mouth adjacent to base of lingual frenulum

- small proportion of mucous acini can be seen in ligher spots among serous acini

- gland and duct share 3 principal nerves: lingual, hypoglossal, facial

sublingual

- smallest major salivary gland

- mixed, predominately mucous

- 5% total salivary volume

- instead of a single large duct, have row of smaller ducts: Bartholin's duct

- ducts open into the mouth along top of transverse ridge on floor of mouth

- supplied by fibers that originate in CN VII (Facial)

minor salivary glands include

- labial (superior, inferior) - lips

- buccal - cheek

- glossopalatine - anterior faucial pillar, glossopalatine fold

- palatine - hard and soft palate, uvula

- lingual - anterior tongue, circumvallate papillae, posterior tongue

labial and buccal minor glands are

mixed, predominantly mucous secretion

glossopalatine and palatine minor glands are

pure mucous

lingual minor glands are

- anterior, circumvallate papillae/Von Ebner's glands: mixed, predominately mucous

- posterior: pure mucous

cllinical considerations

- with age, loss of gland tissue occurs

- gradual reduction of 30-60% in acinar volume of major glands

- viruses can infect and replicate in salivary gland cells and shed into saliva (CMBV, EBV, HPV 6 and 7)

- viral infections like mumps, bacterial infections of individual glands may cause inflammation and result in painful edema

- ductal obstruction may result from siaoliths (stones) in most commonly submandibular duct

- glands may be affected by benign/malignant tumors

- glucose in saliva may affect plaque metabolism

- autoimmune disease after tissue/organ transplantation may cause salivary tissue destruction, thus reduced salivary flow

- function may be affected by individuals with AIDS, rates of flow decreased, lower level of secretory immunoglobulins

- parotid gland enlargement may occur because of lymphadenopathy, lymphoepithelial cysts

- pathologic changes in glands may be observed in cystic fibrosis

Xerostomia

- frequent clinical complaint

- loss of function or reduction in volume may lead to oral dryness

- dries oral tissues and loses protective function of salivary buffers, proteins, mucins

- tissues more susceptible to infections and speech, eating, swallowing difficulty

- side effect of medications

- drugs may cause central/peripheral inhibition of secretion

- destruction of gland tissue is cause of this

- radiation therapy for head and neck cancer can cause this

- highly sensitive to deleterious effects of radiation

- chemo treatment for cancer or bone marrow transplantation may reduce function

- autoimmune disease (Sjogren's syndrome) may cause progressive loss of function from invasion of lymphocytes into gland, destruction of epithelial cells

- sipping water or artificial saliva may help

- pilocarpine may help (parasympathomimetic drug)

xerostomia infection susceptibility include

- Candidiasis

- Periodontal disease

- Lichen Planus

- Burning mouth

- Aphthous ulcers

- Dental caries

diagnostics

- trace amounts of biochemicals in blood serum that filter into mouth

- HIV and cancer has proteins and substances linked to them from serum to saliva

- inc concentrations of these compounds make saliva potentially promising diagnostic fluid with advantages over blood

- advances in science of oral fluid diagnostics lead to ID of disease signature patterns of candidate biomarkers

- increase knowledge of proteome, microbial composition, antimicrobial and enyzmatic activities

salivaomics

- integrated analysis of multiple large scale molecular readouts from important biological fluid

- genomics, epigenomics, transcriptomics, proteomics, microbiomics, metabolomics

- biopsy from saliva