ORAL MUCOUS MEMBRANE

Ankur Tyagi

BDS 1st year

DEFINITION AND GENERAL CONSIDERATION

Epithelium Basement Membrane Lamina Propria Sub mucosa

Basic Structure Of The Oral Mucosa

EPITHELIUM Membranous tissue composed of one or more layers of cells

separated by very little intercellular substance and forming the covering of most internal and external surfaces of the

body and its organs.

SIMPLE SQUAMOUS EPITHLIUM Cells are so thin that

bulging are produced by nucleus

SIMPLE CUBOIDAL EPITHELIUM The length and breadth

of the cell are equal Nuclei are rounded

SIMPLE COLUMNAR EPITHELIUM The length of the cells

is much greater than their width

The nuclei are oval being elongated in the same direction as the cells

They lie near the bases of the cells

STRATIFIED SQUAMOUS EPITHELIUM (NON-

KERATINIZED) Only the most superficial

cell are squamous The cells in the basal layer

are columnar Middle layer are polyhedral Nuclei are oval in the basal

layer Rounded in the middle Transversely elongated in

the superficial layer

STRATIFIED SQUAMOUS EPITHELIUM

(KERATINIZED) The layers are the

same as that of non-keratinized

Has 1 addition layer on top of the flattened cells called keratin layer

EPITHELIUM

Oral mucous membrane resemble skin in many ways

Oral mucous membrane also has 2 layers Epithelium Connective tissue

Together called dermis It is also similar to intestinal mucosa because it has

Epithelium Lamina Propria Submucosa

EPITHELIUM However in the intestinal mucosa another layer is

present called Muscularis Mucosae This layer is present between the Lamina propria

and submucosa Epithelium in the skin is always orthokeratinized Oral mucosal epithelium may be

non-keratinized or keratinized

Keratinization is further divided into 2 types Orthokeratinized Parakeratinized

Differences Between

Keratinized oral mucosa Non Keratinized oral mucosa

Epithelium- Thickness is less

Layers- 4 layers of cells of distinct morphologies

Stratum Basale

Stratum Spinosum

Stratum Granulosum

Stratum Corneum

Thickness is more

Layers- 3 layers of cells of distinct morphologies

Stratum Basale

Stratum Intermedium

Stratum Superficialis

Classification On The Basis Of Degree Of Keratinization

Keratinized Oral Mucosa 1. Orthokeratinized oral mucosa – The epithelium whose surface

layer/squames stains bright pink and does not contain any nuclei. This layer is also called Cornified or Horny layer.

eg. Hard Palate , filiform papilla

2. Parakeratinized oral mucosa – The epithelium whose surface layer stains for keratin (eosinophilic) but shrunken/pyknotic nuclei are

retained in the surface layer. eg. Gingiva , transitional zone of lip

Non Keratinized Oral Mucosa eg. Lining mucosa- lip, cheek , vestibular fornix, soft palate ,

alveolar mucosa & floor of mouth

EPITHELIUM The content of dermis and lamina differ

considerable Skin appendages

Hair follicles Sebaceous glands Sweet glands

These are not seen in the lamina propria Likewise salivary glands are not seen in dermis Papillae of connective tissue protrude towards the

epithelium carrying blood vessels and nerves Epithelium is formed into ridges that protrude

BASEMENT MEMBRANE A complex arrangement links epithelium and

connective tissue components of oral mucosa

BASEMENT MEMBRANE

BASEMENT MEMBRANE This structure has 2 names

Basement Membrane

Basal Lamina

BASEMENT MEMBRANE Basement Membrane

Evident at light microscope level This zone is 1-4 um wide, relatively cell free Stains positive with acid-schiff method This means it has neutral mucopolysaccharides

BASAL LAMINA Basal Lamina

Evident at electron microscopic level and is epithelial in origin

Basal complex has lamina and fibers Basal lamina is made up of 2 layers

Lamina Lucida Lamina Densa

LAMINA LUCIDA This zone is called the clear zone This is present directly below the epithelial

cell layer This layer is 20-40 nm thick This layer has glycoprotein called laminin that

cements non-fibrillar type IV collagen in the lamina densa to epithelial cells

LAMINA DENSA Also knows as dark zone This is present beyond lamina lucida and

adjacent to connective tissue 20-120 nm thick Consists of type IV collagen coated on each

side by glycosaminoglycan heparan sulphate

BASAL LAMINA Thick collagen fibrils attach onto the lamina

densa with finer fibrils running through these to link the whole complex mechanically to connective tissue

Fibronectin has some time been found in the lamina densa and may play a role in adhering fibroblast and proteoglycans to it

Cells are attached to the basal lamina by hemidesmosomes

BASAL LAMINA

Basal lamina provide mechanical adhesion between oral epithelium and lamina propria

Acts as a molecular barrier and plays a role in response to tissue injury

Anchoring fibrils which contain type VII collagen form loops and are inserted into lamina densa

Collagen fibres of type I and II run through these loops