Dr. Ali Tahir
 Moist
lining of GIT, Nasal passages &
body cavities that communicate with the
exterior
 The mucous membrane of oral cavity is
called “Oral Mucosa”
 Located anatomically between skin & GIT
mucosa & shows some properties of both
 Because of its various functions, it is
considered an organ
Dr. Ali Tahir, M.Phil (Part I)

Protection
• From mechanical forces & abrasion while chewing
food & from micro-organisms resident in the oral
cavity

Sensation
• Temperature, Touch, Pain, Taste
• Receptors for Satisfaction of thirst, Swallowing,
gagging, salivation

Secretion
• Major secretion is saliva
• Major & minor salivary glands
• Sebaceous glands are frequently present (upper lip
& buccal mucosa) sometimes called Fordyce’s spots
but their secretions are insignificant
• May be an accident of embryologic development
Dr. Ali Tahir, M.Phil (Part I)
Two parts
1. Outer vestibule (bounded by lips &
cheeks)
2. Oral cavity proper (separated from
vestibule by teeth & gingiva)
• Superiorly bound by hard & soft palate
• Inferiorly by floor of mouth & tongue
• Posteriorly by pillars of fauces
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
 Lining Mucosa
• Constitutes the large part (60%)
• Soft, pliable
 Masticatory mucosa
• 25%
• Firm, immobile
• Gingiva & hard palate
 Specialized mucosa
• Dorsum of tongue, in the form of papillae
• Unique to oral cavity
• 15%
Dr. Ali Tahir, M.Phil (Part I)
 Oral
mucosa is more deeply coloured
compared to skin
 B/c of
• Concentrated & dilated blood vessels
• Thickness of epithelium
• Degree of keratinization
• Amount of melanin
 Inflamed
mucosa is more red b/c of
dilation of blood vessels
Dr. Ali Tahir, M.Phil (Part I)
 Two
main components
• Stratified Squamous Epithelium (oral
Epithelium)
• Lamina Propria
 Interface
b/w these two is irregular
consisting of C.T papillae & rete
ridges/pegs
 Basal lamina separates the two
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
Keratinized Epithelium
Hard palate gingiva & tongue
 Basal cell layer
 Prickle cell layer
 Granular cell layer
 Keratinized layer
Non-keratinized Epithelium
Buccal mucosa, floor of mouth, ventral surface of tongue
 Basal cell layer
 Prickle cell layer
 Intermediate cell layer
 Superficial cell layer
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
A
layer of loose fatty or glandular
connective tissue may be present
between the oral mucosa & underlying
bone/muscle
 This layer contains blood vessels,
nerves & minor salivary glands
 Composition of submucosa determines
the flexibility of the attachment of oral
mucosa to underlying stuructures
 Eg, in gingiva & hard palate, oral
mucosa is directly attached to
periosteum & no submucosa is present.
This is called mucoperiostium & is firm
and inelastic
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
 In
several regions, nodules of lymphoid
tissue consisting of crypts formed by
invaginations of the epithelium into the
lamina propria are present
 Mostly present in posterior parts of oral
cavity
• Lingual tonsils
• Palatine tonsils
• Pharyngeal tonsils
 Together
form Waldeyer’s ring
 Small nodules may also be present in
soft palate, ventral surface of tongue &
floor of mouthDr. Ali Tahir, M.Phil (Part I)
 Consist
of tightly packed cells called
keratinocytes
 Maintains its structural integrity by a
continuous process of cell renewal
 Two types of cell population
• Progenitor cells
• Maturing cells
 Cells
produced by mitosis in the deeper
layers (basal & parabasal layers) migrate
to the surface layers
Dr. Ali Tahir, M.Phil (Part I)
 Dividing
cells are present in clusters at
the bottom of epithelial ridges
 Progenitor population consists of two
groups
• Stem cells (slow cell cycle)
 Produce basal cells & retain proliferative potential of
tissue
• Amplifying cells
 Increase the no. of cells available for maturation
 After
division, each daughter cell
recycles in the progenitor population or
enters the maturing population
 Time required to replace all the cells in
the epithelium is called Turnover time
Dr. Ali Tahir, M.Phil (Part I)
 Wide
range of estimates have been made
 52-75 days for skin
 4-14 days for gut
 41-57 days for gingiva
 25 days for cheek
 Non-keratinized epithelium turns over
faster than the keratinized
Dr. Ali Tahir, M.Phil (Part I)
 Cancer
chemotherapy drugs block
the life cycle of cancer cells as well
as normal host cells
 Cells with short turnover time are
most affected. These include
• Blood cells precursors in bone marrow
• Intestinal epithelium
• Oral epithelium
 Leads
to formation of oral ulcers
 In addition, inflammation also affects
rate of mitosis
Dr. Ali Tahir, M.Phil (Part I)
 Epidermal
growth factor
 Keratinocyte growth factor
 Interleukin-1
 Transforming growth factor α and ß
Dr. Ali Tahir, M.Phil (Part I)
 Present
on masticatory mucosa (hard
palate, gingiva, parts of dorsal surface of
tongue)
 Inflexible, tough, abrasion resistant,
tightly bound to lamina propria
 Process of maturation is called
keratinization or cornification
Dr. Ali Tahir, M.Phil (Part I)
Basal cell layer (stratum basale)
Cuboidal or columnar cells containing
bundles of tonofibrils. Site of most cell
divisions
 Prickle cell layer (stratum spinosum)
Larger, ovoid cells with conspicous tonofibril
bundles, upper part of layer contains
membrane-coating granules
 Granular cell layer (Stratum granulosum)
Flattened cells, keratohyaline granules
associated with tonofibrils
 Keratinized (stratum corneum)
Extremely flattened & dehydrated cells with
loss of all organells, cells filled with fibrillar
material. If pyknotic nuclie retained, called
Dr. Ali Tahir, M.Phil (Part I)
para-keratinized

Basal cell layer (stratum basale)
Cuboidal/columnar cells containing separate
tonofilaments
 Prickle cell layer (stratum spinosum)
Larger ovoid cells containing dispersed
tonofilaments, membrane coated granules in
upper part of layer
 Intermediate layer (stratum
intermedium)
Slightly flattened cells containing dispersed
tonofilaments & glycogen
 Superficial layer (stratum superficiale)
Slightly flattened cells, dispersed
tonofilaments, glycogen, fewer organelle,
nuclie

Dr. Ali Tahir, M.Phil (Part I)
 Cells
of basal layer are least
differentiated cells
 Contain organelles & certain structures
such as tonofilaments & desmosomes
 Tonofilaments are fibrous proteins &
belong to the class of intermediate
filaments
 Aggregate to form bundles called
tonofibrils
 Chemically represent cytokeratins which
are chracteristic constituents of epithelial
cells
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
 Represent a large family of
 Classified according to the
weight & charge. E.g..
proteins
molecular
• Low molecular weight (40kDa) found in glandular &
simple epithelia
• Intermediate molecular weight found in stratified
epithelia
• High molecular weight (67kDa) in keratinized
stratified epithelia
 Keratinzed epithelium has
• Type1, 5, 6, 10, 14, 16
 Non-keratinized epithelium
• Type 4, 5, 13, 14, 19
Dr. Ali Tahir, M.Phil (Part I)
has
 Cohesion
b/w cells is provided by
protein-carbohydrate complexes
produced by epithelial cells themselves
 In addition, modifications of adjacent cell
membranes of cells called desmosomes
provide attachment into which
tonofilaments insert
 Adherence b/w epith & C.T is provided
by hemidesmosomes which attach the
cells to basal lamina
Dr. Ali Tahir, M.Phil (Part I)
 Two other types of connections are
• Gap junctions
• Tight junctions
 Gap junction:
• Membranes of adjacent cells run closely together
separated by a small gap
• Small interconnections are present
• Gap junctions allow electric/chemical
communication
 Tight junction
• Adjacent cell membranes are tightly apposed
Dr. Ali Tahir, M.Phil (Part I)
 Also called lamellate granules
 Are small memrane bound structures
about
250nm in size containing glycolipid,
originate from golgi complex
 Appear in the upper part of prickle layer
 They are elongated in keratinized & circular
in non-keratinized epithelium
 In the upper part of stratum
granulosum/intermedium, these granules
appear to fuse with superficial cell
membrane to discharge their contents into
intercellular space
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
 Cells
in the superficial part of granular
layer develop a thickening on the intracullular aspect of their membrane
 It contributes in resistance of keratinized
layer to chemical solvents
 One of the major constituent of this
thickening is a protein called involucrin
Dr. Ali Tahir, M.Phil (Part I)
 Found in keratinized epithelium
 Contains keratohyalin granules, which
are
basophilic granules under light microscope
 These are irregular in shape
 0.5-1nm in size
 Synthesized by ribosomes
 Intimately associated with tonofibrils
 Facilitate aggregation & formation of crosslinks b/w cytokeratin filaments
 Proteins making bulk of these granules are
called Loricrin
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
As the cells of granular layer reach the
junction with the keratinized layer, a sudden
change occurs
 All organelles are lost, including nuclie &
keratohyalin granules
 Cells dehydrate & assume the shape of
hexagonal disks
 These are called squames
 Squames are lost within days, a process
called desquamation & replaced by cells
from underlying layers
 Limit the colonization of pathogenic microorganisms
 Keratin layer in oral cavity may be upto 20
layers of squames

Dr. Ali Tahir, M.Phil (Part I)
A
slight increase in size occurs in
intermediate cell layer
 Accumulation of glycogen in cells of
surface layer
 Occasionally keratohyalin granules are
seen but these aren’t associated with
tonofilaments
 These granules may remain upto the
surface layer
Dr. Ali Tahir, M.Phil (Part I)
 Cells
in the superficial layer are slightly
more flattened
 Contain dispersed tonofilaments, retain
nuclie & do not dehydrate
 Thus are tolerant to compression &
distension
Dr. Ali Tahir, M.Phil (Part I)
 Some
variation of anatomical locations
of keratinized & non-keratinized
epithelium may occur
 Hyperkeratosis of keratinized oral
epithelium is physiological to chronic
irritation
 Hyperkeratosis of non-keratinized
epithelium can be associated with
abnormal cellular changes that can
lead to cancer
 Inflammation of gingiva can lead to loss
of keratinization or parakeratinization
 These changes are usually reversible
when irritant is removed
Dr. Ali Tahir, M.Phil (Part I)
 Oral
epithelium is largely impermeable
& lacks absorptive capacity
 Epithelium at the floor of the mouth,
however, is thin & more permeable
comparatively (Nitroglycerin to relieve
angina pain)
 Oral epithelium thus limits the
absorption of toxins from microorganisms except in dentogingival
junction
Dr. Ali Tahir, M.Phil (Part I)

Melanocytes
• Present in basal layer
• Lack desmosomes & tonofilaments
• Dendritic, synthesis of melanin pigment granules
(melanosomes)

Merkel Cells
• Present in basal layer
• Non-dendritic, tactile sensation

Langerhans cells
• Dendritic
• Present in parabasal layer
• Antigen trapping & processing

Lymphocytes
• Variable location
• Inflammatory response
• B or T cells
Dr. Ali Tahir, M.Phil (Part I)

Two types of pigmentation is seen in oral
mucosa
• Endogenous
• Exogenous
Endogenous pigments in oral mucosa are
melanin & hemoglobin
 Melanocytes are derived from neural crest
ectoderm
 Enter the epithelium at 11th week of
gestation
 Melanosomes are injected into adjacent
keratinocytes by long dendritic processes
that often pass through several layers of
epithelium
 Groups of melanosomes can be seen under
Dr. Ali Tahir, M.Phil
(Part I)
light microscope,
called
melanin granules

Dr. Ali Tahir, M.Phil (Part I)
 Light
& dark individuals have the same
number of melanocytes, the difference
results from the activity of melanocytes
 In persons with heavy melanin
pigmentaion, melanophages are seen in
the connective tissue
 In oral mucosa, melanin pigmentation is
most commonly seen in gingiva, buccal
mucosa, hard palate & tongue & is more
in dark skinned individuals
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
 Oral
melanotic macule
• Increased production of melanin pigment
without proliferation of melanocytes
 Nevus
(Mole)
• Benign proliferation of melanocytes
 Melanoma
• Malignant tumour of melanocytes
• Melanoma of oral cavity is aggressive
Dr. Ali Tahir, M.Phil (Part I)
 Exogenous
• Caused by foreign material introduced locally or
systemically
• One of the most common oral exogenous
pigment is amalgum
• Gives rise to bluish-gray patch called amalgum
tattoo
• Systemic administration of metals such as lead &
bismuth can cause gingival margin pigmentation
(called Burton’s line)
Dr. Ali Tahir, M.Phil (Part I)
Stratum distendum is another name for
 Submucosa of lining oral epithelium
 Prickle layer of non-keratinized
epithelium
 Superficial layer of Non-keratinized
epithelium
 Granular layer of keratinized epithelium
Dr. Ali Tahir, M.Phil (Part I)
The superficial cells of granular layer of
keratinized oral epithelium have intracellular thickenings to resist chemical
solvents containing which proteins?
1. Cytokeratins
2. Glycoproteins
3. Involucrin
4. Filaggrin
Dr. Ali Tahir, M.Phil (Part I)
 Blood
flow in oral mucosa is the greatest
in which region
1. Soft palate
2. Floor of mouth
3. Gingiva
4. tongue
Dr. Ali Tahir, M.Phil (Part I)
 In
1.
2.
3.
4.
infants, Suckling Pad refers to
A thickened vermillion zone
A thickened intermediate zone
A thickened labial mucosa
A thickened muco-cutaneous junction
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)
Dr. Ali Tahir, M.Phil (Part I)