Salivary Gland Comp And Func2

Salivary gland anatomy and function

Types  2) 3) 4)

Major Parotid Submandibular Sublingual

 2) 3) 4) 5)

Minor Buccal Labial Palatal Lingual

Mixed

Secretion

Serous

Mucous

Parotid gland  1st

to develop and last to be encapsulated  Lymphatic's are entrapped in the parenchyma of the gland  Salivary epithelial cells are often entrapped in these lymph node which may give rise to warthins tumor.  Other major salivary glands DON’T HAVE intraparenchymal entrapments

Location

External features - pyramid  2. 3. 4. 5.

Surfaces - 4 Superior Superficial Anteromedial Posteromedial

 2. 3. 4.

Borders -3 Anterior Medial Posterior

Parotid capsule  Investing

layer of deep cervical fascia  Splits to enclose the gland  Superficial lamina thick and adherent attached to zygomatic arch Deep lamina thin and attached to styloid process, mandible below and tympanic plate above Stylomandibular ligament

Relation - external 

Apex –a) overlaps the posterior belly of digastric b) cervical branch of facial and two division of retromolar comes out through it



Superficial surface –

skin and fascia containing anterior branches of great auricular nerve and lymph nodes

Relation 

Anteromedial – a) posterior border of mandible b)masseter, c)lateral surface of TMJ, d) emerging branches of facial nerve



Poseriomedial surface – a) mastoid process

 Anterior

border – structure emerging through It are a) duct b) terminal branches of facial nerve c) transverse facial vessel  Posterior border separates superficial and posteriomedial surface

 Medial

border is related to lateral wall of pharynx

Relations – internal

Facial nerve relation  Emerges

out of stylomastoid foramen  Almost immediately comes in relation with parotid gland  Enters through posteriomedial surface divides into five branches and leaves through anteromedial surface  Folded or interwoven?

Branches of the Facial N  The

nerve then gives rise to 2 divisions:  1) Temperofacial (upper)  2) Cervicofacial (lower)  Followed

by 5 terminal branches:  1) Temporal  2) Zygomatic  3) Buccal  4) Marginal Mandibular  5) Cervical

Facial Nerve

Parotid gland duct  Stensen’s

duct is 5

cm long.  Arises from the anterior part of the gland and runs over the masseter one finger below the zygomatic arch to pierce the buccinator and open opposite the second upper molar tooth

Parotid Duct orifice  Clinical

examination of the parotid gland should include examination of the duct orifice opposite the upper 2nd molar for signs of inflammation, and palpated for stone  Parotid Sialogram is performed by injecting a contrast through a canula placed in the orifice of the duct

Nerve supply  Parasympathetic

nerves are secretomotor reach the gland through auriculotemporal nerve

Nerve supply

 Symphathetic

fibers are vasomtor and derived from plexus around external carotid artery  Sensory nerves come from auriculotemporal nerve but parotid fascia is innervated by greater auricular nerve c2

Frey syndrome, gustatory sweating  Usual

after parotidectomy  Caused by regeneration of secretory fibers of parotid gland to sweat glands in its area of distribution  So the sweat glands respond to nerve impulses that should provoke the parotid secretion  starch-iodine test is used

Treatment  Medical

- antiperspirants,, 3% scopolamine cream.  Surgical -tympanic neurectomy

Blood supply  Supplied

by external carotid artery and its branches that arises near the gland  Drains into internal external jugular vein

Submandibular gland  Anterior

part of digastric triangle  “J” shaped, indented by mylohyoid muscle  Large part superficial to muscle and small part deep to it

Capsule  Enclosed

in capsule formed by deep cervical fascia  Loosely attached unlike parotid gland fascia hence can be shelled out  The superficial lamina is attached to base of the mandible and deep fascia is attached to mylohyoid line

Superficial and Deep Relations  Superficially:

The skin, the platysma, the capsule (deep fascia), the cervical branch of Facial Nerve, and the Facial Vein  Deeply: the deep aspect lies against the mylohyoid for the most part. But posteriorly lies on the hyoglossus and comes in contact with the lingual and hypoglossal nerves.  Both nerves lie on the hyoglossus as they pass forward to the tongue

The facial Artery  Arches

over its superior aspect to reach inferior border of the mandible and then ascends on to the face in front of the masseter

Submandibular duct

 In

its terminal course it may receive a major sublingual duct called bartholins duct  Sublingual papilla lateral to the freenum

Blood supply  Supplied

by facial artery  Veins drain into common facial and lingual vein

Sublingual gland    



Long flattened body situated in the shallow depression on the mandible called as sublingual fovea Covered by thin mucous membrane and causes elevation called as salivary eminence it is a glandular complex since there is no common duct for all the lobules But the major part of the gland drains into Bartholins duct which latter drains into Warthons duct or opens close to it Dozen or more small ducts called duct of Rivinus open directly in to the oral cavity from the upper border of the gland

Nerve supply - Parasympathetic

contd  Sensory

from the lingual nerve  Parasympathetic from the plexus around the facial artery

Effect of nerve stimulation  Superior

salivatory nucleus for submandibular and sublingual  Inferior salivatory nucleus for parotid  Parasympathetic Stimulation results in abundant, watery saliva with a decrease in [amylase] in saliva  Stimulation by the sympathetic nervous system results in a scant, viscous saliva rich in solutes with an increase in [amylase] in the saliva

 For

all of the salivary glands, these fibers originate in the Superior Cervical ganglion and travel with arteries to reach the glands:  1) External Carotid artery for the Parotid  2) Lingual artery for the Submandibular, and  3) Facial artery in the case of the Sublingual.  Parasympathetic Interruption to salivary glands results in atrophy, while sympathetic interruption doesn’t cause a significant change.

Minor salivary glands - lingual  Anterior

part of tongue near its inferior surface - gland of Blandin  Base of the tongue at the dorsal surface - the von Ebner gland –empties in into vallat papillae

saliva

– composition and function

THE SECRETORY UNIT The basic building block of all salivary glands



ACINI - water and ions derived from plasma



Saliva formed in acini flows down DUCTS to empty into the oral cavity.

TWO STAGE HYPOTHESIS OF SALIVA FORMATION Most proteins

Water & electrolytes

Na+ Cl- resorbed

Some proteins

Isotonic primary saliva

electrolytes

K+ secreted

Hypotonic final saliva into mouth

contd  Resting

condition – sodium and chloride ions are 1/10th of plasma concentration potassium is 7 times more than in plasma bicarbonate is 2 – 3 times more than in plasma

 During

maximal stimulation sodium and chloride potassium  Effect of aldostoron  Excess loss of saliva to the exterior of body may lead to hypokalemia and paralysis

Composition

Inorganic components

Calcium and phosphate  Calcium  sublingual

> submandibular > parotis

 Phosphate  Help

to prevent dissolution of dental enamel  pH around 6 - hydroxyapatite is unlikely to dissolve  Increase of pH - precipitation of calcium salts => dental calculus

Hydrogen carbonate  Buffer  Low

in unstimulated saliva, increases with flow rate  Pushes pH of stimulated saliva up to 8  pH 5,6 critical for dissolution of enamel  Defence against acids produced by cariogenic bacteria  Derived actively from CO2 by carbonic anhydrase

Other ions  Fluoride 

Low concentration, similar to plasma

 Thiocyanate

Antibacterial (oxidated to hypothiocyanite OSCN- by active oxygen produced from bacterial peroxides by lactoperoxidase)  Higher conc. => lower incidence of caries  Smokers - increased conc. 

 Sodium,

potassium, chloride  Lead, cadmium, copper 

May reflect systemic concentrations - diagnostics

Organic components Saliva composition

Organic components of saliva           

Mucins Proline-rich proteins Amylase Lipase Peroxidase Lysozyme Lactoferrin sIgA Histatins Statherin Blood group substances, sugars, steroid hormones, amino acids, ammonia, urea

Multifunctionality

Amylases, Cystatins, Carbonic anhydrases, Histatins, Mucins, Histatins Anti­ Peroxidases Buffering Bacterial Amylases, Cystatins, Mucins, Lipase Anti­ Mucins Digestion Viral Salivary Families Mineral­ Anti­ ization Cystatins, Fungal Histatins Histatins, Proline­ Lubricat­ rich proteins, Tissue ion &Visco­ Statherins Coating elasticity Amylases, Cystatins, Mucins,  Mucins, Statherins Proline­rich proteins, Statherins adapted from M.J. Levine, 1993

Mucins  Lubrication  Glycoproteins

- protein core with many oligosaccharide side chains attached by Oglycosidic bond  More than 40% of carbohydrates  Hydrophillic, entraining water (resists dehydration)  Unique rheological properties (e.g., high elasticity, adhesiveness, and low solubility)  Two major mucins (MG1 and MG2)

Amylases – (ptyalin) α(1-4) bonds of starches such as amylose and amylopectin  Maltose is the major end-product (20% is glucose)  Considered to be a good indicator of properly functioning salivary glands  Parotid gland saliva has highest content(80%)  Its action is inactivated in the acid portions of the gastrointestinal tract and is consequently limited to the mouth.  Provides disaccharides for acid-producing bacteria  Hydrolyzes

Lingual Lipase  Secreted

by lingual glands and parotis  Involved in first phase of fat digestion  Hydrolyzes medium- to long-chain triglycerides  Important in digestion of milk fat in new-born

Statherins  Calcium

phosphate salts of dental enamel are soluble under typical conditions of pH and ionic strength  Supersaturation of with calcium and phosphates maintain enamel integrity  Statherins prevent precipitation or crystallization of supersaturated calcium phosphate in ductal saliva and oral fluid  Also an effective lubricant

Proline-rich Proteins (PRPs)  40%

of AAs is proline  Inhibitors of calcium phosphate crystal growth Present in the initially formed enamel pellicle and in “mature” pellicles

Lactoferrin  Iron-binding

protein  Links to free iron in the saliva causing bactericidal or bacteriostatic effects on various microorganisms requiring iron for their survival such as the Streptococcus mutans group.

Lysozyme  Present

in numerous organs and most body fluids  Hydrolysis of β(1-4) bond between Nacetylmuramic acid and Nacetylglucosamine in the peptidoglycan layer of bacteria.  Gram

negative bacteria generally more resistant than gram positive because of outer LPS layer  aggregation and inhibition of bacterial adherence

Histatins A

group of small histidine-rich proteins  Potent inhibitors of Candida albicans growth  The bactericidal and fungicidal effects occur through the destruction of their architecture and altering their permeability.

Cystatins  Are

inhibitors of cysteine-proteases  Are ubiquitous in many body fluids  Considered to be protective against unwanted proteolysis  bacterial

 May

proteases

inhibit proteases in periodontal tissues

Salivary peroxidase systems  Sialoperoxidase

(SP, salivary peroxidase)

Produced in acinar cells of parotid glands  Also present in submandibular saliva  Readily adsorbed to various surfaces of mouth 



enamel, salivary sediment, bacteria, dental plaque

 Myeloperoxidase

(MP)

From leukocytes entering via gingival crevice  15-20% of total peroxidase in whole saliva 

Components of the peroxidase anti-microbial system  Peroxidase

enzymes (SP or MP)  Hydrogen peroxide (H2O2)  oral

bacteria (facultative aerobes/catalase negative) produce large amounts of peroxide  S.

sanguis, S. mitis, S. mutans

 Thiocyanate

ion (SCN-) which is converted to hypothiocyanite ion (OSCN-) by peroxidase

Thiocyanate reactions H2O2 + SCN­  More

SP and/or MP

OSCN­ +H2O

acid favors HOSCN  Due to uncharged nature, HOSCN penetrates bacterial cell envelope better

HOSCN/OSCN--mediated cell damage  can

oxidize sulfhydryl groups of enzymes  block glucose uptake  inhibit amino acid transport  damage inner membrane, leading to leakage of cell  disrupt electrochemical gradients

Immunoglobulin  Secretory

immunoglobulin A (IgA) is the largest immunologic component of saliva. It can neutralize viruses, bacterial, and enzyme toxins  It serves as an antibody for bacterial antigens and is able to aggregate bacteria  IgG and IgM, occur in less quantity and probably originate from gingival fluid.

Tissue Repair Tissue repair function is attributed to saliva since clinically the bleeding time of oral tissues appears to be shorter than other tissues  Experimental studies in mice have shown wound contraction is significantly increased in the presence of saliva due to the epidermal growth factor it contains which is produced by the submandibular glands 

Xerostomia – symptom not a disease  2. 3. 4.

Temporary Calculi Psychological Drugs

 2. 3. 4.

Permanent Aplasia Removal of gland Sjogrens syndrome

Factors affecting flow of saliva  Individual

Hydration  Body Posture- Patients kept standing up or lying down present higher and lower SF, respectively  The Circadian and Circannual Cycle  Medications- antidepressants,, antipsychotics, antihistaminics, and antihypertensives)  Age  Gender  Lighting