https://userupload.net/3ppacneii1wj Toxicologic Pathology (Second Edition), 2010 INTRODUCTION The oral mucosa is, in many ways, similar to the skin in its architecture, function, and reaction patterns. This section only emphasizes those characteristics of the oral mucosa that influence or result in a distinct group of pathologic entities. Because of its location at the entrance of the digestive and respiratory tracts and its proximity to the teeth, the oral mucosa is subjected to numerous natural and man-made xenobiotics. The peculiar architecture and absorption characteristics of the oral mucosa, especially in areas of extreme thinness, coupled with the rich microorganism flora of the mouth, makes the oral mucosa a peculiar site deserving separate discussion.

1. ORAL MUCOUS MEMBRANE
1
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2. CONTENTS
 INTRODUCTION
 DEFINITION
 FUNCTIONS
 CLASSIFICATION
 COMPONENTS OF ORAL MUCOSA
 AGE CHANGES IN ORAL MUCOUS MEMBRANE
 CLINICAL CONSIDERATIONS
 CONCLUSION

3. INTRODUCTION
The skin, oral mucosa and intestinal lining, all consist of two
separate tissue components, which are, the covering epithelium
and an underlying connective tissue. As these tissues, together
perform a common function, the oral mucosa must be
considered as an organ.
Understanding the complex structure of a tissue or organ
often is easier, when it’s function is known. The structure of oral
mucosa reflects a variety of functional adaptations. Any change
in these functional adaptations, leads to pathology.

4. DEFINITION
“The term moist
membrane is used to
describe moist lining of
GIT, nasal passages and
other body cavities that
communicate with exterior.
In the oral cavity this lining
is called oral mucous
membrane.”

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6. FUNCTIONS
Protection : Separates and protects deeper tissues and
organs from mechanical stresses/ forces, and external
environment.
Sensation : Temperature, touch and pain sensation.
Tongue has taste buds. Reflexes like swallowing,
gagging, salivating, also are initiated by receptors in oral
mucosa.

7. 7
• Secretion : Saliva is secreted by salivary glands
and contributes to the maintenance of a moist
surface.
• Thermal regulation : In some animals (dog),
considerable body heat is dissipated through oral
mucosa by panting. For these animals, oral mucosa
plays a major role in regulating of body
temperature. This function is not active in humans.

8. 8
Absorption : Certain substances like nitrates are
absorbed from sublingual region.
Excretion : Excretes metabolites.
Aesthetics : Gingiva and lip mucosa enhance facial
esthetics.

9. Oral Mucous Membrane
Classification
1-Keratenized mucosa ( Masticatory mucosa)
(A) Gingiva (B) Hard palate
2- Non-keratenized mucosa (Lining mucosa)
(A) Firmly attached (B) Loosely attached
I- Soft
palate II-lip III-cheek IV-ventral
S tongue
I- Floor of
mouth
II-Vestibule
III-alveolar
mucosa3- Specialized mucosa
Dorsal surface of tongue
9

10. HISTOLOGY OF ORAL MUCOSA
There are mainly 2 components
1. oral epithelium made up of stratified squamous epithelium
2. underlying connective tissue called lamina propria
• the interface between epithelium and connective tissue is usually
irregular and upward projections of connective tissue called the
connective tissue papillae
• these papillae interdigitate with epithelial ridges
• the structural interface between epithelium and connective tissue
called the basement membrane
10

11. Oral Mucous Membrane
Epithelium
Lamina Propria
Submucosa
Periosteum
Bone
11

12. THE EPITHELIUM
• It is derived from the embryonic ectoderm
• The cells vary from cuboidal to flat squamous cells
• This epithelium may be keratinized or non keratinized
depending upon the functional requirements
• Keratinized epithelium may be ortho or para keratinized
12

13. 13
• Epithelial cells are called keratinocytes
as they contain within the cells fine
filaments called tonofilaments.
• These are fibrous proteins synthesized
by ribosomes.
• When tonofilaments form bundles of
filaments they are called tonofibrils.
• Tonofilaments are formed in keratinized
epithelium only.
• Bundles of tonofilaments attach to an
intercellular thickening called
Attachment Plaque Which in turn
adhere to an oval or circular area of
adjacent cell membrane called
DESMOSOME.

14. 14
• The attachment of epithelial cells
to one another is by desmosome.
• The attachment of epithelial cell to
connective tissue is by Hemi
Desmosome.
• A basal lamina seperates the
epithelium & lamina propria.
• It has an upper clear layer called
Lamina Lucida in contact with the
basal cells of the epithelium &
lower dense layer called Lamina
Densa which is contact with
reticular layer of lamina propria.
• The cells of the basal cell layer are
connected to the lamina lucida by
Hemidesmosomes.

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16. EPITHELIAL MATURATION
16
PATTERNS OF MATURATION
Keratinization Non-Keratinization

17. 17
Stratum Basale
Stratum Spinosum
Stratum Granulosum
Stratum Corneum.
KERATINIZED EPITHELIUM

18. 18

19. Stratum basale :
• They are present above the
basement membrane.
• They have cuboidal or
columnar cells.
• Cells of the basal layer shows
most mitotic activity.
• This layer is also called
Germinative layer.
• They are attached to the
basement membrane by
hemidesmosomal junction.
19

20. Stratum Spinosum :
• Arranged in several rows.
• Cells are larger elliptical or
spherical in shape
• Cells are fused together due to
the presence of intercellular
bridges or desmosomes.
• Cells of spinous layer are joined
together by intercellular bridges
giving the cells a prickly
appearance
• They contain glycolipids
originating from golgi complex.
20

21. 21
Stratum Granulosum :
• Cells of stratum granulosum
are flat and are found in
layers of three to five cells
thick
• This layer is prominent in
keratinized epithelium (and
absent in nonkeratinized
epithelium)
• These cells have
keratohyaline granules in
their cytoplasm
• Keratohyaline granules help
to form the matrix of the
keratin fibres found in the
superficial layer

22. Stratum Corneum :
• Cells are flat, devoid of nuclei
and full of keratin filament
surrounded by a matrix
• These cells are continuously
being sloughed and are
replaced by epithelial cells
that migrate from the
underlying layers
• The cells are usually
dehydrated
• In case of orthikeratinized
layer there is no retension of
nuclei
• In parakeratinized layer there
is retention of nuclei 22

23. NON KERATINIZED EPITHELIUM
23
Stratum basale
Stratum intermedium
Stratum superficial / stratum
distendum

24. Stratum basale :
• This layer is similar to that of keratinized
epithelium.
• Only difference is that the cells of this layer in non
keratinized epithelium are slightly larger than that
of keratinized epithelium.
• Intercellular bridges are less conspicuous.
24

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26. Stratum Intermedium :
• Glycogen is present
• Rarely keratohyaline granules are also visible at this
level, but they are not associated with tonofilaments.
Stratum Superficiale :
• Cells appear slightly more flattened than other layers.
• They contain dispersed tonofilaments and nuclei and
dehydrated cells.
• This surface is flexible and tolerant to compression and
distension.
26

27. KERATINIZED & NON-KERATINIZED
MUCOSA
Stratum basal
Stratum
spinosum
Stratum
intermedium
Stratum
granulosum
Stratum
superficial
Keratohyaline
Gs.
Keratenized epithelium Non-keratenized epithelium
Stratum cornium
27

28. LAMINA PROPRIA
• Found below the epithelium
• Has 2 parts and are
1.Papillary
2.Reticular
• Papillary portion is projections of
connective tissue into the epithelium
• Increase in length of papillae is seen in
areas where additional mechanical
adhesion is required between
epithelium and connective tissue
• Eg; masticatory mucosa
• Reticular portion is present below this
layer
• This contain mainly collagen fibres
blood capillaries
28

29. • SUBMUCOSA----- It is a
connective tissue of varible
thickness
• Serves primarily as attachment
for lamina propria to the
underlying bone or muscle
• Submucosa contains glands
adipose tissues vascular and
neural components
29

30. KERATINOCYTES
Constitute the major part of epithelial cells
The cells are arranged in different layers
During maturation they either change to keratin or share in
keratin formation
These cells have the following criteria:-
 Always present in sheets & attached to each other by one or
more type of cellular junctions
 Cytoplasm of these cells is stained with H & E
 Cytoplasm contains the tonofilaments
30

31. NON-KERATINOCYTES
Present in both keratinized & non-keratinized
epithelium & have the following criteria:-
• Appear as clear cells by ordinary H&E stain, they
need special stains
• Present as scattered cells & not in sheets
• A clear hallows around their nuclei
• Their cytoplasm is free from tonofilaments
• No cellular junctions
• Do not play any role in synthesis of keratohyaline
granules or keratin
31

32. 32
LANGERHANS’ CELLS
• Are found in the stratum spinosum &, occasionally in
stratum basale.
• These cells have long, thin extensions of the cytoplasmic
membrane, called dendrites.
• They can be distinguished from keratinocytes by the
absence of desmosomes & tonofilaments.
• Can be distinguished from the melanocytes by the
absence of premelanosomes.

33. 33
•Contains the rod shaped or
racquet shaped birbeck’s
granules, which allows for
positive identification at the
ultrastructural level.
•Are antigen presenting cells.
•They engulf antigens from the
external environment & the
intracellular lysosomes split the
antigens into peptide
components. These fragments
are then transferred to T-
lymphocytes.

34. 34
MERKEL CELLS
• Are situated in the basal layer
of the gingival epithelium.
• Possess occasional
desmosomes &
tonofilaments.
• Are usually associated with
an axon terminal.
• The merkel cell & associated
axon terminal form a complex
that serves as a touch
receptor.
• Are usually found in groups
or clusters.

35. 35
MELANOCYTES
• Are melanin producing cells located in the basal
layer of the gingival epithelium.
• These cells arise from the neural crest.
• Lack tonofibrils, desmosomes & hemidesmosomes.
• Are highly dendritic in nature.
• The most characteristic feature of the melanocyte is
the melanosome granule found within the cytoplasm.

36. 36
• A more heavily pigmented
gingiva is due to the
production of melanin & its
subsequent uptake by the
epithelial cells.
• There is a great variability in
the location & distribution of
melanin in the oral cavity.

37. 37
• Present variably.
• Contains large circular
nucleus
• Cytoplasm is scanty with few
organelles.
• No desmosomes and
tonofilaments present.
• Associated with inflammatory
response in oral mucosa.
Lymphocytes(Inflammatory cell) :

38. KERATINIZED MUCOSA
(MASTICATORY MUCOSA)
During mastication, parts of oral mucosa are subjected
to forces & pressure
 Gingiva
 Hard Palate
38

39. • GINGIVA is a masticatory
mucosa and covers the
alveolar process of the jaw
and surrounds the neck of
the teeth.
• The gingival extends from
the dentogingival junction
to the alveolar mucosa.
• The stratified squamous
epithelium may be
keratinized or non-
keratinized but most often
it is parakeratinized.
39

40. TYPES OF GINGIVA
The gingival is divided into
three types:
A)Free or unattached or
marginal gingival
B) Attached gingiva.
C) Interdental papilla
40

41. A) FREE OR UNATTACHED OR
MARGINAL GINGIVA:-
• It is that part of the oral mucosa that
surrounds the necks of the teeth and
forms the free margin of the gingival
tissue
• It is differentiated apically from the
attached gingival by the free gingival
groove
• The inner side of it forms the gingival
sulcus
• The free gingival mucosa is
composed of stratified squamous
epithelium that may be keratinized,
parakeratinzed or sometimes
nonkeratinized 41

42. Attached gingiva:
• The attached gingiva lies
between the free gingival
groove and the alveolar
mucosa
• The junction of the attached
gingiva and the alveolar
mucosa is called
mucogingival junction
• In healthy mouth attached
gingiva shows stippling
(orange-peel appearance)
which is a characteristic of
this type of mucosa
42

43. Interdental Papillae :
• Part which extends between
two teeth up to the contact
point is called interdental
papillae.
• It has a ‘facial side’ and a
‘lingual side’ .
• It’s margins are concave.
• Due to inflammation,
interdental papillae looses it’s
concavity
43

44. COL :
• Connecting facial and lingual
side of the interdental papilla
(on proximal side) is an
epithelial structure called
COL.
• It’s concave shape means,
gingiva is healthy.
• It becomes dome shaped, in
gingival recession and
inflammation.
• It is covered by non
keratinized stratified 44

45. Gingival fibres
Bind attached gingiva to the alveolar
bone & tooth.
4 groups:
1. Dentogingival fibres: from cervical
cementum to lamina propria; most
numerous.
2. Alveologingival fibres: from
alveolar crest into Lamina Propria
3. Circular fibres: circle the tooth.
4. Dentoperiosteal fibres: from
cementum into periosteum of
alveolar crest & surface of
alveolar bone.
45

46. MICROSCOPIC FEATURES OF GINGIVA
Broadly speaking gingival is
made up of epithelium and
connective tissue.
The gingival epithelium can
be studied under three
headings:-
• Outer or oral epithelium
• Sulcular epithelium
• Junctional epithelium.
46

47. Oral epithelium:
• Faces the oral cavity, is
parakeratinised, shows rete pegs
and connective tissue papillae
Sulcular epithelium :
• Faces the tooth without contacting
it. Thin non-keratinised stratified
squamous epithelium (no
granulosum and corneum layers),
extends from the coronal end of
the junctional epithelium to the
crest of the gingival margin.
• Acts as a semi-permeable
membrane.
47

48. Junctional epithelium :
• Provides contact between gingiva &
tooth.
• Stratified squamous non-keratinised
epithelium.
• 3-4 cells thick in early life, increasing to
10-20 later.
• Derived from the reduced enamel
epithelium
• Attachment to tooth: inner basal lamina
• Attachment to gingival connective tissue:
outer basal lamina
48

49. Hard palate
• It is keratinized masticatory
mucosa.
• It is pink in color which is
firmly attached to underlying
structures
Macro-Anatomy of hard palate
Palatine gingiva:
Adjacent directly to the teeth
which is similar to the previously
described gingiva but
mucogingival junction is not
present.
49

50. 50
Median palatine raphe:
• Extends from the palatine papilla posteriorly.
• Palatine papilla (incisive) is pear shaped & is formed of dense
C.T. that contains the oral part of naso-palatine duct (this duct is
lined by simple or pseudostratefied columnar epithelium rich in
goblet cells).
• In median palatine raphe, it is difficult to differentiate between
lamina propria & submucosa.
• Radiating from this raphe, transverse folds called palatine rugea
which is formed of dense C.T. covered by epithelium.

51. 3- The anterolateral area (fatty
zone)
This area present between the
raphe & the gingiva anteriorly.
 Its lamina propria is fixed to
periosteum by bands of fibrous
C.T. dividing the submucosa into
compartments containing fat cells.
4- The postero-lateral area
(glandular zone)
- Present posterior to the fatty
zone.
- The submucosa contains pure
mucous glands.
 The fatty and glandular
zones act as cushion.
 The C. T. of hard palate is
thick anteriorly than
posteriorly.
Submucosa
Fatty
zone
Glandular
zone
Epitheial rete
pegs are tall &
numerous
Mucosa
51

52. Non-Keratinized Mucosa
(Lining Mucosa)
Present in areas not subjected to high levels of friction but is
mobile & distensible
Firmly attached to underlying muscles
 Soft Palate
 Lip
 Cheek
 Ventral Surface of tongue
Loosely attached to underlying structures as bone, fascia or
muscle
 Floor of mouth
 Vestibule
 Alveolar Mucosa
52

53. • Thicker than masticatory mucosa.
• Non keratinized.
• flexible; withstand streching.
• Interface with C.T is smooth.
• Lamina propria is thicker with fewer collagen
fibres(irregular).
• Elastic fibres provide extensibility.
• Attached to muscle by collagen & elastic fibres:
retraction of mucosa during mastication.
53

54. Lip and cheek Vestibular fornix &
alveolar mucosa
Inferior surface of
tongue & Floor of
oral cavity
Soft Palate
Epithelium Non keratinized
stratified
squamous
Non keratinized
stratified squamous
Non keratinized
stratified squamous
Non keratinized
stratified squamous
Lamina propria Short irregular
papillae
Short irregular
papillae.
• In the fornix
mucosa loosely
attached to the
underlying
structures.
• In alveolar mucosa
papilla may be
totally missing
• Floor of the mouth
papillae are short.
• On the inferior
surface of tongue
short but numerous
Has distinct layer of
elastic fibres
separating it from sub
mucosa. Connective
tissue papillae few and
short
Sub mucosa Sub mucosa has
strands of loose
connective tissue
with fat & small
mixed glands
A sub mucosa of loose
connective tissue seen
in alveolar mucosa.
No muscle fibres
present
• Sub mucosa in floor
of mouth has
adipose tissue.
• In inferior surface
of the tongue a
separate sub mucosa
cannot be identified
Relatively loose and
contains plenty of
mucous glands
54

55. Specialized Mucosa
• Dorsal Surface of Tongue
• The connective tissue binds the epithelium
to the underlying skeletal muscle
• The epithelium is modified, keratinized,
stratified covered with papillae, which can
be seen by naked eye
The different papillae found on the dorsal
surface of the tongue are:
1. Filliform papillae
2. Funginform papillae
3. Circumvallate papillae
4. Foliate papillae
55

56. 2 parts:
• Anterior 2/3: 1st
pharyngeal arch ;c/as
body; TG nerve; papillary
portion.
• Posterior 1/3: 3rd
pharyngeal arch;c/as
base;IX nerve; lymphatic
portion(lingual tonsil).
• Separated by V shaped
groove c/as sulcus
terminalis.
56

57. Filiform papillae :
• Anterior tongue.
• Cone shaped structure.
• C.T core covered with thick
keratinized epithelium-
velvety appearance of
tongue.
• Tough abrasive surface so
function as masticatory
mucosa.
• Build up of keratin leads to
elongation.
• Increased keratinization
leads to hairy tongue.
• No taste buds. 57

58. Fungiform papillae :
• Scattered between
numerous filiform papillae
at the tip of tongue.
• Smooth, round structures;
mushroom shaped.
• Red- highly vascular C.T
core & thin non
keratinized epithelium.
• Taste buds present on
superior surface.
58

59. Circumvallate papillae
• 8-12 in no.
• Adjacent & anterior to
sulcus terminalis.
• Surrounded by deep,
circular groove into which
ducts of von ebner salivary
glands open.
• C.T core covered by
keratinized epithelium
superiorly.
• Lateral walls- non
keratinized epithelium &
taste buds. 59

60. Foliate papillae:
• Foliate papillae are
located in the furrows
along the posterior sides
of the tongue
• They may be lined with
taste buds
• They are not prominent in
human beings
60

61. Papillae are mainly
concerned with different
taste sensations :
Vallate papillae : Bitter
Fungiform papillae :
Sweet and salty
Foliate papillae : Sour
61

62. Taste bud :
♦ Present in
1) All tongue papillae except
filiform.
2) Soft palate.
3) Posterior surface of
epiglottis.
• They are intraepithelial
structure, barrel or ovoid
with rounded base resting
on B.M & end with narrow
opening toward the
epithelial surface & called
taste pore. Flattened small
epithelial cells surround
the taste pore.
62

63. Histology of the taste bud:
• Each taste bud is composed of
about 3 modified epithelial cell
type.
• Outer supporting
(sustentacullar) cells arranged
like layers of onion & are in
contact with neighboring
epithelial cells.
• Inner supporting
(sustentacular) cells, they are
shorter & rode shape cells.
63

64. 64
• Taste cells (Neuroepithelial
cells) they are 11-12 in
number & present between
the inner supporting cells.
• These cells are slender with
dark stained nucleus &
apically stiff bristle-like
process extends to the space
beneath taste pore.
• Nerve plexus present in C.T.
below the taste bud, some
fibers enter it & end in contact
with the taste cells.

65. Lingual tonsil:
- Present as small rounded or
oval elevations due to
aggregation of lymphatic
nodules in underlying C.T
known as lingual follicles.
Histologically
- Lingual follicles covered by St
Sq Epith (non-keratinized)
which extended down in many
sites to form lingual crypt. The
lymphatic tissue surrounds
the crypt & composed of
germinal centers & lymphatic
tissue fills the spaces
between these centers. 65

66. 66
- Ducts from underlying
Weber mucous salivary
gland open into the bottom
of lingual crypt.
- Lingual tonsil forms a part of
the lymphatic ring between
mouth & nose from one side
& pharynx on the other side.

67. AGE CHANGES IN ORAL MUCOSA
• Oral mucosa of an elderly patient has a smoother and
dryer surface than younger patient, due to dry therapy or
any systemic diseases.
• Epithelium appears thinner histologically.
• Flattening of epithelial ridges.
• Reduction in no. of filiform papillae.
• Langerhan’s cells become fewer with age, leading to
decrease in cell mediated immunity.

68. 68
• Decrease in cellularity occurs in lamina propria
with increase in collagen.
• Sebaceous (Fordyce’s spots) glands of lips and
cheeks increase with age.
• Elderly post menopausal women, have
symptoms such as dryness of mouth, burning
sensations and abnormal taste.

69. CLINICAL CONSIDERATIONS
69
• The oral mucosa can change according to
various factors, including smoking, age &
disease.
• Over 7% of the total number of cancers
diagnosed in the United States are located in the
oral & oropharyngeal areas.
• The process of keratinization can be altered in
cancerous & precancerous lesions such as
leukoplakia.

70. 70
• Thinning of the epithelium occurs in relation to
prosthetic devices covering the surface of the
mucosa.
• Changes in salivary flow- due to age, radiation or
disease- disrupt the normal maturation &
differentiation of the epithelial cell layers.
• The healing capacity of the oral mucosa is greater
than that of the skin. Orthognathic surgery to move
segments of the mandible & maxilla can be performed
using an intraoral approach to take advantage of
these characteristics.

71. CONCLUSION
71
Oral mucous membrane maintains the integrity of the oral
cavity in health & disease. Knowledge regarding the
mucosa aids in detecting any changes from normalcy
which would pave the way for diagnosing various disorders
which affect the mucosa & thus, providing treatment for the
same. Also as public health dentists, educating people
regarding the detection of changes in the mucosa would
help in early diagnosis & hence focus on prevention
ensured.

72. 72
REFERENCES
• S.N. Bhaskar. Orban’s, oral histology and embryology.
11th Edition, Mosby: 1998; p – 345-385
• Neville BW, Damm DD, Allen CM, Bouquot JE. Oral
and maxillofacial pathology, 2nd edition. Philadelphia :
W.B. Saunders ; 2002.
• Richard Tencate, Oral histology development,
structure and function. 5th edition, 1998 : p 345-385.
• Carranza F.A., Michael G. Newman. Clinical
peridontology 8, 9,10th edition