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Objectives:
At the end of this subject students should know thoroughly:
1- The definition & function of oral mucous membrane.
2- The classification of oral mucous membrane.
3- The histological structure of the mucous membrane.
4- The differences between the two different types of the oral
epithelium.
5- Keratinocytes and non keratinocytes.
6- The macro &micro-anatomy of the gingiva.
7- The macro &micro-anatomy of the hard palate.
8- The different types of lining mucosa.
9- The specialized mucosa and the different types of the
papillae.
10- Dento-gingival junction (Histology and Histogenesis)
Mucous membrane
Hard
palate
Dorsal
surface of
the tongue
Check
mucosa
Ventral surface
of the tongue
Floor of
mouth
Gingiva
Alveolar mucosa
Vestibular
fornix
Labial mucosa
Definition
-It is that membrane which lines a body cavity
that communicates to outside and coated with
serous and or mucous secretion.
- Its epithelial cells have a high rate of turnover.
- It possesses a stratified epithelium which is
keratinized in many places and prevents or limits
diffusion across it in both directions.
Functions of oral mucosa
1- Protective
It protects the underlying structures from mechanical,
chemical and thermal effects of food taken.
It acts as a biological barrier against bacteria and invasion of
their toxins.
2- Sensory
It has multi nerves that respond to temperature, touch and
pain as well as to taste sensation.
Certain receptors in the oral mucosa initiate reflexes such as
swallowing, gagging, salivation and water satisfaction.
3- Thermal regulation
In animals through the evaporation of water from the
surface mucosa .
Human oral mucosa plays a minor role in this respect.
4- Secretory
Salivary secretion keeps it always moist and provides
it with additional protective means.
Classification of oral mucous
membrane
1-Keratenized mucosa ( Masticatory mucosa)
(A) Gingiva
(B) Hard palate
2- Non-keratenized mucosa (Lining mucosa)
(A) Firmly attached
I- Soft
palate
II-lip
III-check
(B) Loosely attached
IV-ventral
S tongue
3- Specialized mucosa
Dorsal surface of the tongue
I- Floor of
mouth
II-Vestibule
III-alveolar
mucosa
Histological structure:
The human oral mucosa consists of:
Epithelium. & Lamina propria, a connective
tissue supporting layer.
Both of these two layers are separated by a
basement membrane and attached either directly
to the underlying structures or through a
submucous layer.
1- The oral epithelium:
It is stratified squamous epithelium keratinized
in certain areas and non-keratinized in others.
Keratenized epithelium
Non-keratenized epithelium
A-The keratinized epithelium:
Found in gingiva and mucosa of hard palate, which are
subjected directly to the mechanical effect of food during
mastication.
The cells are arranged in four different layers:
Basal (stratum basale)
Spinous (stratum spinosum)
Granular (stratum granulosum)
Cornified (stratum cornium).
These cells are called
Keratinocytes.
Stratum
spinosum
Stratum basale
These cells have the following criteria:
a- Always attached to each other by one or more type of
cellular junctions.
b- The cytoplasm of these cells is stained with ordinary stain
as H & E.
c- Their cytoplasm contains characteristic tonofilaments.
*The cells of the basal and
spinous layer are named stratum
germinativum or progenitor cells.
*Daughter cells pass towards the
surface and during the process of
maturation, take on the
appearance characteristic of the
various layers.
a. Basal Cell layer (stratum Basal).
-It consists of a single layer of high cuboidal cells
rest on the basement membrane.
-Protoplasmic process projecting from their basal
end towards the C.T.
By the E. M.
- The cytoplasm contains tonofibrils forming desmosomes
and hemi -desmosomes which attach the cells to one another
and to the Basal lamina.
- The desmosomes consist of thickening of adjacent cell
membrane a pair of attachment plaques and intervening extra
cellular structure and tonofilaments.
- The hemidesmosomes consist of a single attachment plaque.
Thickening of one cell membrane extracellular structure that
attach the epithelium to the Basal lamina and tonofilaments.
The desmosomes
1- Thickening of the adjacent
cell membrane.
2- A pair of attachment plaque.
3- Tonofilaments.
4- Extracellular structure.
The hemi-desmosomes and basal lamina
Both layers derived
from the basal cell
layer
b-The spinous cell layer (Stratum Spinosum).
- Above the basal cell layer.
- Formed of several layers of polyhedral cells joined by long
intercellular Bridges which gives the cells a prickly
appearance.
-They are small in size with
wide intercellular spaces.
By the E.M.
The prickle cells are the most active in protein synthesis so
they contain: 1- Nuclei show widely spread chromatin.
2. Well developed Golgi apparatus.
3. Rough endoplasmic Reticulum with its Ribosomes.
4. Numerous Mitochondria.
There is a progressive decrease in synthetic activity through
the layer directed to the surface.
Low synthetic activity
High synthetic activity
Odland Bodies or Keratinosome :
- They are membrane coating granules.
- Present in the superficial layer of the prickle cells.
- It has an internal Lamellated structure.
- It may originate from the Golgi system.
They are present also in the lower granular cell layers.
Odland body
Role of Odland bodies
-These structures are responsible for the thickening of the
cell membrane which occurs during Keratinization.
-In the more superficial layers of the stratum spinosum the
granules come to lie close to the cell membrane.
c-The granular cell layer
Lies above the prickle cell layer and is made up of several
rows.
- Cells are Flat with degenerated and Pyknotic nuclei and
many organelles are reduced
- They synthesis protein also but with diminished rate.
-Cells contain basophilic granules called Keratohyaline
granules.
-These granules are 0.5-1.0 μm in length and form the
matrix in which the tonofilaments are embedded.
-The Odland Bodies are increased and discharged into the
intercellular spaces.
-This is associated with the development of a barrier in the
epithelium that limits the movement of substances between
the cells.
-The tonofilaments are increased and associated with the
Keratohyaline granules.
d-The cornified layer:
- Made up of keratinized squamae which are larger and
Flatter than the granular cells.
-These cells are characterized by loss of all organelles
-They are filled entirely with
closely backed tonofilaments.
-These cells finally will
desquamate.
-This layer provides the mechanical
and chemical protective function to
the mucosa.
2- Non keratinized epithelium
Stratum
superficial
Stratum
intermedium
Odland body
Stratum basal
Non-keratenized epithelium
Non-keratinized oral epithelium:
The epithelium is thicker than the keratinized
one
- It doesn’t produce cornified surface layer.
- It has no stratum granulosum nor stratum
cornium.
- It has 3 cell layers.
1. Stratum Basal (Basal cell layer ).
Similar to that of the Keratinized
type.
2. Stratum Intermedium
-Formed of large polyhedral cells
with short intercellular Bridges and
small intercellular spaces.
-The cells do not have prickly
appearance.
-There are Odland bodies with
different size and location than that in
the Keratinized epithelium.
3. Superficial cell layer. (Stratum
Superficial).
-It consists of nucleated flat cells
which ultimately desquamate as the
cornified layer.
-There is accumulation of glycogen
and occasionally Kerato hyaline
granules appear more regular and not
associated with tonofilaments.
-Function of keratohyaline granules appear
to be associated with thickening of the cell
membrane.
-These granules may contribute to the
internal thickening of the cell
membrane.
Keratinocytes
and non-keratinocytes
Keratinocytes are those cells of keratinized and
non keratinized epithelium.
Non Keratinocytes are: Melanocyte, Langerhans
cell, Merkel ‘s cell and Inflammatory cells.
Criteria of Keratinocytes
a- Always attached to each other by one or more type of
cellular junctions.
b- The cytoplasm of these cells is stained with ordinary stain
as H & E.
c- Their cytoplasm contains characteristic tonofilaments.
Criteria of Non Keratinocytes
a- They do not attach to each other or to the epithelial cells
except Merkel’s cells.
b- The cytoplasm of these cells does not stain by H & E.
c- Their cytoplasm does not contain tonofilaments except
Merkel’s cells.
1- Pigment cell
(Melanocyte, blast)
2- Langerhan’s cell
3- Merkel’s cell
Shape
Small body with long
slender and branched
process present in
Similar in shape.
the Inter cellular
Contain granules
spaces of epith.
(langerhan’s granules)
contain melanin
granules
(melanosomes)
Location
Basal and parabasal
layers
High level cell and may Basally in
be found at lower
epithelium
levels.
Stain by Not stained so called
H&E
( Clear dentritic cell )
Not stained so called
( Clear dentritic cell )
Special
stain
Gold chloride
DOPA reaction ( for
tyrosinase enzyme)
They do
not have
long processes.
Contain small
membrane bounded
granules
Not stained so
called
( Clear but not
dentritic cell )
Origin
Neural crest cells
Bone marrow
Neural crest cells
Cell
No tonofilaments.
junction No desmosomes.
No tonofilaments.
No desmosomes.
-Little tonofilaments.
-Little desmosomes.
-Nerve cell seen to be
associated with the cell
with synapse-like cleft.
Function
They may be
Responding to touch.
described as
1-Neural element.
2- Degenerated
melanocyte.
3- Intra epithelial
Macrophage.
4- Regulatory cells
(control epith. Cell
division and
differentiation)
5- Uptake and
processing of antigen
in contact allergic
reaction
Pigmentation.
If melanosomes
engulfed by
epithelial cell
called
(Melanophore) or
by C.T. cell
(Melanophage).
4- Inflammatory cells
They are transient cells
IILamina propria.
The lamina propria is divided into 2 layers,
1- A superficial layer: loose connective tissue called the
papillary layer which is formed of tall numerous papilla
directly under the basement membrane and collagen
fibers arranged in a loose network with fine argerophelic
Fibers.
Papillary layer
2-The deeper layer is made of dense and closely
packed collagen fibers which are arranged in laminae,
and this layer is called the Reticular layer.
The papillary layer may be absent while the Reticular
layer is always present.
No line of demarcation is present between the two
layers.
Papillary layer
Reticular layer