Histology

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HISTOLOGY OF ORAL MUCOUS
MEMBRANE & IT’S CLINICAL
IMPLICATIONS
Dr. Sudeep M Chaudhari
1st
year PG
Dept of Pedodontics & Preventive Dentistry

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Contents
● Introduction
● Classification
● Function
● Structure of oral epithelium
A)Oral epithelium
I) Keratinized epithelium
1)Stratum basale
2)Stratum spinosum
3)Stratum granulosum
4) Stratum corneum
II)Non-keratinized epithelium
B)Lamina propria
C)Submucosa

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Contents
● Subdivisions of oral mucosa
I. Masticatory mucosa
II.Lining mucosa
III.Specialized mucosa
● Clinical considerations
● Conclusion
● References

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Introduction
● Body cavities that communicate with the external
surface are lined by mucous membranes, which are
coated by serous and mucous secretions.
● The surface of the oral cavity is mucous membrane.
The oral mucosa is continuous with the skin of the lip
through the vermilion border.Posteriorly it is
continuous with the mucosa of the pharynx.
● It’s structure varies in an apparent adaptation to
function in different regions of the oral cavity.

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Classification
➔ Based upon primary function served :-
1.Masticatory mucosa (gingiva and hard palate)
2. Lining or reflecting mucosa (lip, cheek, vestibular
fornix, alveolar mucosa, floor of mouth and soft
palate)
3.Specialized mucosa (dorsum of the tongue and taste buds)

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➔ Based upon keratinisation
1. Keratinised
-Orthokeratinized
-Parakeratinized
2. Non-keratinised.

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➔ Based upon Location
1. Buccal Mucosa.
2. Lingual Mucosa.
3. Palatal Mucosa.
4. Labial Mucosa.
5. Alveolar Mucosa.

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(1) Defense-
• Integrity of the oral epithelium
is an effective barrier for the
entry of the micro-organisms.
• Oral cavity contains wide
variety of micro-organisms
• Oral mucosa is impermeable
to bacterial toxins
(2) Lubrication-
● Secretion of salivary glands keeps
the oral cavity moist
● A moist oral cavity helps in
speech, mastication, swallowing
& perception of taste
(4) Protection-
● Oral mucosa protect deeper
tissues from masticatory forces
& from abrasive nature of
foodstuff
(3) Sensation-
● Temperature (heat and cold),
touch, pain
● Reflexes such as swallowing,
gagging and salivation
Function

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Structure Of Oral Mucosa
A)Epithelium
B)Lamina Propria
C)Submucosa

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A)Oral Epithelium
➔ Epithelium of the oral mucosa is stratified squamous
epithelium
➔ May be – I)keratinized orthokeratinized
parakeratinized
– II)nonkeratinized

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➔ Cytokeratin forms the cytoskeleton of all epithelial cells,
along with microfilaments & microfibrils.
➔ Cytokeratin is seen not only in cell but also in cell
contact area like desmosomes.
➔ It provides mechanical linkages & distribute forces over
the wide area.

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I)Keratinized Epithelium
Has keratinocytes
arranged in four cell
layers
1)Stratum basale
2)Stratum spinosum
3)Stratum granulosum
4)Stratum corneum

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➔ A single cell, at different time, is a part of each layer.
➔ After mitosis, it may remain in the basal layer & divide
again or it may get pushed upward.
➔ During migration – biochemical & morphological
changes occurs – this is termed as differentiation.
➔ Differentiation ends with the formation of keratinized
squama.
➔ After reaching the surface it is shed off, this process is
called as desquamation.

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➔ The process of cell migration from basal layer to the
surface – maturation.
➔ The time taken for cell divide & pass through the entire
epithelium – turnover time
• Skin : 52 – 75 days
• Gut : 4 – 14 days
• Gingiva : 41 – 57 days
• Cheek : 25 days
• Junctional Epithelium : 5 - 6 days

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1)Stratum basale
➔ Made up of single layer of
cuboidal cells.
➔ Synthesize DNA &
undergoes mitosis.
➔ Shows ribosomes &
elements of rough
endoplasmic reticulum –
indicative of protein
synthesis.
➔ Proteins of basal lamina &
proteins which form the
intermediate filaments of
the basal lamina.

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2)Stratum
spinosum
➔ Made up of polyhedral
cells which are larger than
basal cells.
➔ Cells are joined by
intercellular bridges.
➔ These cells are most
active in protein synthesis.

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3) Stratum
granulosum
➔ Contains flatter & wider
cells which are larger than
spinous cells
➔ Contains basophilic
keratohyalin granules
➔ Nuclei shows sign of
degeneration & pyknosis
➔ Still synthesizes protein
➔ Cell surface become more
regular

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➔ At the same time, the
lamellar granule, a small
organelle (keratinosomes /
Odland body / membrane
coating granule) forms in
the spinous & granular
layer – these granules
discharge their contents
into the intercellular space
forming an intercellular
lamillar material – which
contributes to the
permeability barrier
3) Stratum
granulosum

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4)Stratum
corneum
➔ Madeup of acidophilic
keratinized squama, which
is larger & flatter than the
granular cell layer
➔ Thickness of this layer
varies at different sites in
the oral cavity
➔ Here all of the nuclei &
other organelles have
disappeared

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Types of keratinized epithelium
➔Parakeratinized Epithelium :The superficial cells i.e.
the cells of stratum corneum are dead but retain the
nucleus
➔Orthokeratinized Epithelium : The nuclei are lost in
epithelium

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II)Non – keratinized epithelium
➔ Nonkeratinized epithelial cells in the superfacial layers
do not have keratin filaments in the cytoplasm
➔ The surface cells also have nuclei
➔ This epithelium is associated with lining of the oral
cavity

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Difference Between Keratinized &
Non-keratinized Epithelium
Keratinized
● Layers – basal,
spinosum,granular,
cornified layer.
● Produce a cornified
surface layer.
● Prickly appearance .
Non-keratinized
● Layers-basal, spinosum,
granular layer.
● Does not produce a
cornified surface layer.
● Intercellular spaces not
obvious-no prickly
appearance.

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Difference Between Keratinized &
Non-keratinized Epithelium
Keratinized
● No nuclei-
orthokeratinised
Pyknotic nuclei-
parakeratinised
Non-keratinized
● Stratum superficiale
contains nucleated cells

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B)Lamina Propria
➔ Connective tissue of
variable thickness that
supports the epithelium is
called as lamina propria
➔ Two layers-
1)Papillary–between
epithelial ridges
2)Reticular
➔ Interlocking arrangement-
increases the area of
contact – to facilitates
exchange of material
between blood vessels &
epithelium

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➔ Ground substance
1)Glycoprotein
2)Proteoglycans
➔ Cells -
1)Fibroblasts
2)Mast cells
3)Macrophages
4)Collagen fibers – type I & type III
5)Elastic fibers
➔ Blood vessles
➔ Nerves

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C)Submucosa
➔ Consists of connective tissue of
varying thickness & density
➔ Attaches the mucous
membrane to the underlying
structures
➔ Contains-
• Salivary glands
• Blood vessels
• Lymph vessels
• Nerves
• Adipose tissue

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Subdivisions Of Oral Mucosa
● Keratinized area
I.Masticatory mucosa
II.Vermilion border of lip
● Nonkeratinized area
I.Lining mucosa
● Specialized mucosa

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I.Masticatory mucosa
1.Hard palate
2.Gingiva
● Immovable, tightly fixed to the periosteum

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1.Hard palate
Zones -
i.Gingival region –
adjacent to the teeth
ii.Palatine raphe–
extending from the
incisive papilla
posteriorly
iii.Anterolateral area –
fatty zone between the
raphe & gingiva
iv.Posterolateral area –
glandular zone

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Histologic Appearance Of Hard Palate

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2.Gingiva
➔ Extends from the
dentogingival junction to
the alveolar mucosa
➔ May be keratinized or non
keratinized but most often
is parakeratinized
➔ The gingiva is limited on
the buccal surface by
mucogingival junction
which separates it from
alveolar mucosa

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Parts of gingiva–
1)Marginal gingiva-
➔The free gingival is the terminal
edge of the gingiva which is
usually about 1mm wide and
surrounds the teeth
➔ The free gingiva forms one of
the walls of the gingival sulcus
and is separated from the
attached gingiva by a groove
called free gingival groove.

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Parts of gingiva–
2) ATTACHED GINGIVA:-
● It is the continuation of the free
gingiva and extends up to the
alveolar mucosa.
● The attached gingiva is
separated from the alveolar
mucosa by a mucogingival
sulcus.
● The width :- →3.5-4.5 mm in the
maxillary anterior region
→3.3-3.9mm in the mandibular
anterior region.
→Posteriorly the width of the
attached gingival is less.

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Parts of gingiva–
3) INTERDENTAL PAPILLA:-
➔It is the part of gingiva that fills the space
between two adjacent teeth.
➔It is a shallow V shaped space surrounding
the tooth.
➔It is bounded on one side by the tooth and
on the other side by the free gingiva.
➔From oral or vestibular aspect, the surface
of the interdental papilla is triangular.

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Parts of gingiva–
4) Col -
➔The depressed part of
interdental papilla is called
Col.
➔Col is covered by thin non-
keratinized epithelium.

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Fig. Histology of gingiva

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II.Vermilion Zone
➔ The trasitional zone between
the skin of the lip & the
mucous membrane of the lip
➔ The line that separates the
skin from the vermilion zone
is termed as the vermilion
border
➔ Keratinized

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Non-kereatinized
Lining mucosa
➔ Found on the
1.lip& cheek
2.vestibular fornix & alveolar mucosa
3.Floor of the mouth
4.Inferior surface of the tongue
5.Soft palate
➔ Relatively thick, non-keratinized epithelium & a thin
lamina propria

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1.Lip & Cheek
➔ Non-keratinized stratified squamous epithelium
➔ Attached firmly – lip – to orbicularis oris
– cheek – to buccinator
➔ Loose connective tissues contains fat & minor mixed
salivary glands
➔ Glands ––– lips – situated in submucosa
––– cheek – glands are larger & usually found
between the bundles of buccinator & sometimes on it’s
outer surface

43. 43Fig.Cheek

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Fig. Histology of Lip

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2. Vestibular fornix & alveolar
mucosa
➔ Non-keratinized
➔ Loosely connected to
the underlying structures
➔ Gingiva and alveolar
mucosa are separated
by the mucogingival
junction
➔ Minor mixed salivary
glands

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3. Floor of the mouth
➔ Non-keratinized stratified
squamous epithelium
➔ Loosely attached to the
underlying structures
➔ Submucosa contains
adipose tissues
➔ Sublingual glands lie close
to the covering mucosa in
the sublingual folds

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4. Inferior surface of the tongue
➔ Non-keratinized stratified
squamous epithelium
➔ Firmly attached to the
connective tissue surrounding
the bundles of the muscles of
the tongue
➔ Highly vascularized

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5. Soft Palate
➔ Non-keratinized stratified
squamous epithelium
➔ Highly vascularized &
reddish in colour
➔ Lamina propria shows a
distinct layer of elastic
fibers
➔ Contains an almost
continuous layer of
mucous glands
➔ Also contains taste buds

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Specialized Mucosa
● Superior surface of the
tongue is rough & irregular
● A “V” shaped line divides it
into anterior part or body
(2/3rd) & posterior part or
base
● Nerve supply-
➢ Body – lingual branch of
trigeminal nerve
➢ Base – glassopharyngeal
nerve
Dorsal Lining Mucosa

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Papillae of The Tongue
1)Filiform papillae
2)Fungiform papillae
3)Circumvallate papillae
4)Foliate papillae

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1)Filiform papillae
● On the anterior 2/3rd
● Numerous, fine painted, cone shaped- gives velvet
appearance
● Keratinized epithelial projections
● doesn’t contain taste buds

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2)Fungiform papillae
● Mushroom shaped, round, reddish
● Scattered between the filiform papillae
● Contain few(1-3) taste buds on their dorsal surface

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3)Circumvallate papillae
● Present in front of V-shaped terminal sulcus
● 8-10 in number
● Lateral surface of the epithelium contain numerous taste
buds
● The duct of small serous glands called von Ebner’s
gland open through it

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4)Foliate papillae
● Present on posterolateral
part of the tongue
● May contain taste buds

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Fig.Tongue Map

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Clinical Considerations

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MUCOCELE
● Salivary gland lesion of
traumatic origin that forms
when the main duct of
minor salivary gland is torn
with subsequent
extravasation of mucous
into the fibrous connective
tissue, so that a cystlike
cavity is produced.
● Most commonly occur on
the lower lip

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Fordyce’s granules
● Sebaceous glands are frequently
included in the line of fusion
between the maxillary and
mandibular processes
●
Are found just beneath the buccal
mucosa along the line of occlusion
●
Usually occur bilaterally, unilaterally
or in groups as small (1-2mm)
slightly elevated colored spots
●
They produce a yellowish rough
plaque
A
B

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Fissured Tongue (Scrotal Tongue)
● Malformation manifested
clinically by numerous small
furrows or grooves on the
dorsal surface
● Often radiating out from a
central groove along the
midline of the tongue
● Is usually asymptomatic
● Although some patients may
complain of mild burning
soreness.

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Geographic tongue(Benign
Migratory Glossitis)
● It consists usually of multiple areas of desquamation
of the filiform papillae of the tongue in an irregular
circinate pattern.
●
The central portion – sometimes appears inflamed
● The border – may be outlined by a thin yellowish line
or band
● The areas of desquamation remain for a short time
on one location then heal and appears on another
location.
●
It may persist for weeks or months and then regress
spontaneously, only to recur at a later date.

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Geographic tongue(Benign
Migratory Glossitis)
● Histologic features - The
hyperplastic epithelium shows
focal collection of neutrophils
designated as Munro’s
abscess within the epithelium.

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Lingual thyroid
●
It is an anomalous condition in which
follicles of thyroid tissue are found in
the substance of the tongue possibly
● Arising from a thyroid anlage which
failed to migrate to its position.
● Clinically it appears early in life
chiefly during puberty and
adolescence.
● It appears as a nodular mass in or
near the base of the tongue in the
general vicinity of the foramen
caecum, most often at the midline.

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Median Rhomboid Glossitis
● This congenital abnormality of the tongue is due
to failure of the tuberculum impar to retract
before fusion of the lateral halves of the tongue.
●
An ovoid or rhomboid- shaped reddish patch on
the dorsal surface of tongue immediately
anterior to the circumvallate papillae.
● It is a flat or slightly raised area and has no
filiform papillae.

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Hairy tongue
● It is characterized by
hypertrophy of the filiform
papillae of the tongue with lack
of normal desquamation and
form a thick matted layer on the
dorsal surface
●
The color may vary from
yellowish white to brown or
even black depending upon
their staining

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Traumatic Ulcers (Decubitus Ulcer)
● May be due to – biting,
toothbrush trauma, external
irritant
● ‘Cotton roll injury’ - most
common iatrogenic injury
● Most commonly occurs – lateral
border of the tongue, buccal
mucosa

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Aphthous Ulcer
● Development of painful,
recurring solitary or
multiple ulcerations
● May be due to- bacterial
infection; immunological
abnormalities; iron, vit.
B12 or folic acid
deficiency, allergy

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Conclusion
For the clinicians to treat dental problems knowledge of oral
mucous membrane is very important. We should check each
and every aspect of oral mucosa while preforming clinical
examination. Sometimes the clinical condition which seems
to be normal may take abrupt changes.

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References
➔ G S Kumar. Orban’s Oral Histology & Embryology 2011,
13th Edition, St. Louis: Mosby Elsevier.
➔ McDonald RE, Avery DR, Dean J. Dentistry for the Child
and Adolescent 2004, 9th Edition, St. Louis: Mosby
Elsevier.
➔ Pinkham, Casamassimo P, Fields H, McTigue D, Nowak
A. Pediatric Dentistry Infancy Through Adolescence
2005, 4th edition, Philadelphia: London : Elsevier
Saunders.
➔ R Rajendran, B Sivapathasundharam. Shafer’s
Textbook of Oral Pathology 2012,7th Edition, St. Louis:
Mosby Elsevier.

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