Oral Histo 10th Lec

8/2/2019 Oral Histo 10th Lec

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Oral histology

Lecture 10How dentogingival junction is developed:

1. As the tooth is located inside the jaw before

it starts to appear , it is covered with

reduced enamel epithelium , (A)

2. This reduced enamel epithelium is joined

with oral epithelium, creating a canal , this

canal is lined by epithelium , thats why its is

called ( epithelium lined canal) , this is the canal through which the

tooth erupt without bleeding. (C)

3. The remaining part doesnt disappear, what remains after full eruption

is a part of reduce enamel epithelium located at enamel .

4. This makes what we call the junctional enamel epithelium of the

gingiva (G)

- junctional enamel epithelium

This is an unique epithelium because it is composed of exhausted cells ,

these are the reminisce of enamel organ so they served a long period of

time of function and finally instead of retiring them we asked them to work .

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These cells are unable to protect against the invasion of bacteria thats why

many people have gingivitis even though they clean their teeth very much!

Eruption is completed before root formation is completed,

- when the tooth emerges into the mouth the root of that tooth is not

completed , the tooth continues to erupt until the tooth makes contact with

the opposing tooth at that stage even the root is not completed yet .

- Lets imagine that our teeth compete their roots before eruption , what

happens ?!

They will not erupt , Our tooth erupt because of root development ,thats

why teeth cannot erupt by themselves , thats why when the tooth reaches

the oral mucosa , it needs about 1-1.5 for deciduous teeth to undergo root

completion, and 23 years for permanent teeth.

- At that stage ( Periods till root completion ) these teeth are verysensitive , if a child had a trauma at this stage during root formation , it is

very likely that the pulp of that tooth will undergo necrosis , and because of

this it will not complete the root , then we have to do root canal treatment

and doing it in such an apex is really difficult , it is also called

Apexsification

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- Radiograph for two central incisor , as you see they are fully erupted but

notice that the APCs are still open because the root is still forming .

Eruption of permanent molars

1. They are non-succors , so they dont have any tooth before them to

resolve their root and to replace them , they erupt by themselves

2. They erupt through alveolar bone , for that reason these teeth are

erupt when they are located inside bone .

3. bone loss occurs before the tooth continue to go up , finally the bone

covering the tooth is lost to allow the tooth to appear in the mouth .

4. Tooth organ epithelium ( reduced enamel epithelium ) makes contact

with oral mucosa causing stretching and thinning for oral mucosacreating a canal that is created by the rupture of oral epithelium .

5. Tooth emerges until clinical contact with the opposing tooth is made .

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Surrounding erupting teeth

The changes taking place above the tooth , we have to discuss the

changes for the surrounding the tooth

Formation begins with root formation

Formation for areas surrounding the tooth starts at the same time of

root formation and continues with it

From delicate fibers parallel to the surface of the tooth into well-

organized fibrous bundles

After the root complete its formation or start to develop the fibers

start to be organized in bundles

Blood vessels become more dominant

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The difference of permanent molar eruption and permanent premolar ,

canines and incisors , is that succor teeth have to get rid of something else

as they go , Even there is a difference between eruption if permanent

molars and deciduous teeth , deciduous teeth are erupting while the bone

is forming around them thats why it is easily , while permanent molar erupt


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We want formation , any process of active formation needs blood

supply

As root elongates more fibrous bundles appear

Fibers increase in density and number as the tooth erupts

Fibers attach and release and re-attach rapidly as the root elongates

( PDL remodeling)

The root is elongating , let's suppose we have a fiber here attach tothe root , if it remains attach to the tooth , it will drop down and break

then the tooth wont erupt , thats why it has to be detached and attach

again to a lower position . ( One of the important theories in tooth

eruption)

Alveolar bone increases in height accordingly ( As the root forms ).

After functional occlusion fibers gain their mature orientation.

Alveolar Process

The alveolar process develops during the eruption of teeth.

This is true for primary teeth but not for permanentteeth because

they develop inside the bone , so the bone is already present and

they have to create their path by resorbing the bone ,but in deciduous

teeth the bone surrounds the root , so the surrounding areas are

forming with the root formation

Grows at a rapid rate at the free border

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Proliferates at the alveolar

crest

No distinct boundary exists

between the body of the

maxilla or mandible and the

alveolar process

It is very difficult to say that this is the bone carrying the teeth and this

is the beginning of the body of the mandible because bone is

continues from the alveolar crest to the areas of mandible or maxilla

If teeth are lost the alveolar bone disappears

When we take the tooth out , the alveolar process start to disappear

gradually, thats why people who lose their teeth at young age , they

remain without teeth for a long period of time , if you come to this

person after a long period of time you will find a very very reabsorbed

alveolar bone .

** Tooth forms and the bone forms around it, thats why the tooth become

surrounded by bone , this bone surrounding or this space where the tooth is

located inside the bone is called Crypt . it increases is height to

accommodate root formation , alveolar bone is deposited appositionally

around the emerging crown , then this leads to the increase in height if the

alveolar bone .

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Look at the picture on the right

A

Deciduous tooth & permanent successor initially

share crypt

B

Bone subsequently forms to encase the


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At first when we have two teeth one

deciduous and one permanent they

share the same bony crypt but after the

eruption of deciduous tooth, after that the

permanent succor tooth develops its own bony surrounding

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Underlying erupting teeth

Occlusal movement provides an underlying space (fundic region).

The tooth is going up , it will leave a space that will immediately filled

by Fibers, thats why this spaces are Highly fibroblastic, they are a

very active fibers that give a Fine strands of fibers that calcify intobone trabeculae (ladder-like arrangement).

As the tooth moves up, bone trabeculae become denser and the

spaces left are filled with bone.

Mechanisms of tooth eruption

The details are not required , you just have to know that the mostacceptable theory is The Role Of PDL !

Conclusion "

Connective tissue surrounding the tooth contains the eruptive

elements - 2 views

- Force is produced by activity of fibroblasts contractility &

motility

- Vascular/hydrostatic pressure in & around the tooth is

responsible for eruption

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Role of PDL fibroblast motility/contractility

Cells exert tractional forces via contractility/motility through

This fibroblasts are attached of a network of collagen , and they have

connection with each other " Cell-to-cell contacts "

Colchicine is a drug that disturbs intracellular microtubules,

intracellular microtubules are the cells that are responsible for the

movement of the cells.

Colchicine retards eruption

Role of PDL vascular/hydrostatic pressure

Vascular pressure can change the position of a tooth in its socket

Tooth moves in synchrony of arterial pulse

At death, blood pressure is zero eruption ceases and stops

Changes is eruptive behavior upon

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- Administration of vasoactive drugs( drugs that are reated too

Blood Pressure )

- Interference with sympathetic vasomotor nerves , that are

responsible for vasoconstriction for blood vessels surrounding the

tooth.

- Stimulation of cervical sympathetic nerves

Other theories of tooth eruption, but they are not very supported

1. Growth of the root

2. Pulpal pressure

3. Detachment & reattachment of PDL fibers

4. Cell proliferation

5. Increased bone formation around the teeth

6. Endocrine

7. Vascular changes

8. Enzymatic degradation

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Theory of Root elongation

When root elongates it needs a space , there is no space because its

surrounding by bone as a result the tooth goes up but it is not very

acceptable

Theory of Pulpal Pressure

1. The area above the tooth which is the

eruption pathway is a degeneration zone,

so the blood pressure inside this area is

almost zero .

2. But the tissues inside the pulp are very

active thats why they are very much innervated so the blood

pressure is high.

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3. And because the pressure differences , the tooth moves up.

Theory of Periodontal ligament fibers

- Attachment release and re-attachment

of the PDL fibrous bundles as a result the tooth

moves up .

Functional Eruptive Phase

A. The last phase of tooth eruption , after the tooth makes contact with

the opposing tooth .

B. But its not the end of eruption , teeth continue to erupt until contact

and you have to imagine that the maxillary tooth is still have force

downward and the mandibular tooth still has a force upward.

C. Both are under force but they dont move because the two forces are

equal .

D. Loss of opposing tooth causes over eruption " Supra Eruption "

E. Continues as long as teeth area present , Once it is removed eruption

stops.

F. Compensation to : 1. Increase in alveolar process height

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2.Attrition/abrasion of incisal/occlusal surfaces

3.Loss of opposing tooth (over eruption)

G. If the tooth continues to erupt , cementum increases , so the toothmoves up slightly creating a space that is going to be filled with extra

layers of cementum . Thats why these supra erupted teeth always

have a thick cementun in the Root apexes and Frication areas.

Oral mucosais the lining of oral cavity

Functions of oral mucosa

Mechanical protection

Barrier against microorganisms & toxins

Immunological defense

Lubrication

Innervation

Touch

Proprioception

Taste

Pain

Structure of Mucosa

Epithelium (vs. epidermis of skin ( upper layer )

Stratified squamous

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Ectodermal in oral mucosa

Basal lamina (the structure that separate the the epithelium from the laminapropria )

Lamina Propria (vs. dermis of skin)

Dense connective tissue to retain and keep epithelium

Papillary Layer

Reticular layer

Ectomesenchyme

Submucosa (vs. subcutaneous tissue)

Loose connective tissue

Contains Glandular tissue

Adipose tissue

Large blood vessels and nerves

Types of oral mucosa

The oral mucosa may be classified into three

types :

Masticatory mucosa

Lining mucosa

Specialized mucosa

Masticatory mucosa :

Where there is high compression & friction

Rough, thicker and whiter in colour compared to lining mucosa

Keratinized or parakeratinized epithelium ( thats why its whiter )

Thick lamina propria bound down directly & tightly to underlying bone

Covering

Hard palate

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It requires for the mucosa to

be in contact with food and to

be supported by bone to be

classified as masticatory

The surface of the tongue contain

masticatory mucosa but because it

contain taste bud its classified as

specialized mucosa


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Oral surface of gingiva

Lining mucosa :

Not subject to high level of friction

Soft, mobile and distensible Thinner & redder in colour compared to masticatory mucosa

Non-keratinized epithelium

Loose lamina propria

Covering

Oral surface of cheeks, lips, alveolus , dentogingival region, floor ofthe mouth, ventral surface of tongueand soft palate

Specialized mucosa:

Keratinized epithelium

Covers

Dorsum of the tongue

Associated with taste sensation

Called Gustatory mucosa

Vermilion zone of the lip

Vermilion zone of lip : its a feature only found in humans and its the area betweenthe skin of the lip and the labial mucosa of the lip in other words its the area

where females apply lipstick.

Layers ( please open the book page 223 fig14.2 )

Stratum germinativum (stratum basale)

Stratum spinosum (prickle cell layer)

Stratum granulosum (granular layer) Stratum corneum (Keratinized or cornified layer)

The most mature cell are the cell on the surface and the less mature cellsare the cell on the base so all the time the process of maturation from the

base toward the surface and the maturation process is towardkritanization So mitotic figures are seen in the basal layer and kertinizedcell are seen in the surface layer

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The alveolus mucosa is in contact

with bone but not with food thats

why its classified as a lining

mucosa

Epithelium


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Once the cell have reached full maturation they are lost and a new layer isformed at the below this process is called turnover

Turnover is fastest in junctional & sulcular epithelia (5 days)

Masticatory mucosa has the slowest turnover

rate because these are tough cells

Stratum germinativum ( stratum basale ) :

Single cuboidal cell layer

Adjacent to lamina propria and separated from lamina

propria by a basement membrane If you remove the

basement membrane there will interaction with lamina

propria leading to something maybe tooth formation

The only layer where mitosis occurs so

you can see mitotic figures

Least differentiated cells

Non-keratinocytes

Stratum spinosum :

Several cells thick

Called spinosum because it has spines

These cells are connected with each other by

desmosomes so when we prepare the section the

cells shrink but the margin are still attached thats

why they look like spines

Round or ovoid cells

Larger & more mature than those of s. germinativum

Contain

Tonofilaments & involucrin

Phospholipid granules (Odland bodies) in upper part of stratum spinosum

Increased desmosomes (shrinkage during preparation gives the spiny

appearance)

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Junctional epithelia is theepithelium binding the gingiva

to enamel

Sulcular epithelia is the inner


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Stratum granulosum :

Called granulosum because it contain granules

Cells of further increase in maturation

Cells larger & flatter

Contain

Tonofilaments & tonofibrils that occupy the cytoplasm

Keratohyaline granules (contain profilaggrin) these granules are theprecursor of keratin

Non-keratinocytes

cell present in the epithelial but have different function than keratinization

10% of oral epithelium

Lack tonofilaments & desmosomes (except Merkel cells)

Appears as clear cells in routine H&E staining because they lack the cytokeratin

of keratinocytes Include

Melanocytes

Langerhans cells

Stratum corneum :

In kertinized epithelium:

Highly mature epithelial cells (squames)

The keratinzation process of the cell could be orthokeratinzation or

parakeratinzation

A. orthokeratinzation : All cellular organelles and nucleus are lost And a very

active build up of keratin in the cell

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Involucrin : is the primary molecule that leads to the

development and formation of the keratin


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B. parakeratinzation : In gingiva, nuclei may be retained

Cells are packed with Keratin

Kertain consists of

Tonofilaments surrounded by Filaggrin (matrix protein)

Desmosomes are weakened to allow forshedding (desquamation)

Involucrin is cross-linked to form a cornified envelopbeneath plasma membrane ( not very important info)

In non kertinized epithelium:

No keratin

Tonofilaments are less & under-developed

Lack keratohyaline granules

This layer is less distinct

stratum superficiale : The outer layers of non-

kertinized epithelium and consist of the two layer

startum corneum and stratum granulosum

stratum intermedium : The layers below and not the same layer in enamel

organ

Keratinization

A process by which cell develop and build up keratin inside them ( intracellular)

Regional distribution so u can find keratinized tissue in places and non

kertinized tissue in other according. To Adaptation to abrasion by food - rough

surface

Whiter than nonkeratinized mucosa becuase keratin has the property of absorbing

water and it swell And anything that absorb water reflect

light thats why it appears whiter in color and because theyare thicker and away from blood vessels

Ortho- vs. parakeratinization as we discussed earlier

Frictional keratosis : keratinization caused by friction

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90% of cells in oral

epithelium are

keratinocyte and 10%


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The buccal mucosa. Could be keratinized due to continuos ( chronic ) bitting of

the buccal mucosa and not very forceful bitting because some people have

different orientation of their molars so the buccal mucosa will be subjected to

friction and start to produce keratin

But if the stimulus ( bitting ) is acute and very forceful it will appear as an ulcerin the buccal mucosa

Look at this epithelium can u distinguish

between the upper two layers?? No thats

why its non-keratinized

Look at the cells they have a clear

cytoplasm because of the absence of

keratin

Melanocytes : (please open the book page 230 fig14.21)

Located in stratum germinativum ( stratum basale)

Not attached by desmosome to another cells

Pigment (melanin)-producing cells

Derived from neural crest cells

Long processes that extend through upper layers

Packed with granules (melanosomes) these are secreted to give the color of skin

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All humans have the same number of melanocyte but the pigmentation differs soa white person have a little amount of pigmentation and a dark person have a hugea mount of pigmentation

Racial variance is due to

A. Melanocyte size difference

B. Number of dendritic processes

C. Melanosomes: granule number or size

D. Melanin: degree of dipersion and rate of degradation

E. But the number of melanocytes are not related

Note: People with very active melanin degradation look whiter than people withslow melanin degradation

Langerhans cells ( please open the book

page230 fig 14.23 )

Dendritic cells ( they have dendrites )

Located in the layers above stratumgerminativum

Derived from bone marrow precursors

Antigen-presenting cells so they engulf any

antigen or any pathogen and present these antigen to lymphocyte

Involved in contact-hypersensitivity reactions, antitumour immunity & graft

rejection so if you put a skin graft and it got rejected, thats because of

antigen presenting cells

Contain Birbeck granules

Merkel cells

these are located in the stratum germinativum of masticatory mucosa, its

a non-masticatory mucosa.

they are absent in the lining epithelium non-keratinized epithelium

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If you see a non-keratinized mucosa,

with cells with a clear cytoplasm at

the base, then its a melanocyte. But

if you see a keratinized mucosa, with

cells with clear cytoplasm at the

base, they can be melanocytes and


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they are closely related to nerve

fibers, thats why they are thought to

act like mechanical receptors, they are

derived from neural crest cells,

they are associated with

desmosomes, so they are the only

non-keratinocytes that are attached to

the surrounding cells.

Q: Merkel cells present what kind of

mucosa?

A: Keratinized mucosa.

Lining Mucosa

Its very difficult to distinguish between different layers, compare it to a

masticatory mucosa, which is very easy to distinguish the keratinized layer

it can be de-attached and separated in preparation.

Now its very difficult to distinguish between the top layers; because the toplayer is similar to the layer below it and it doesnt look keratinized, because

keratin usually doesnt stain pink, it accept slight pink color. Thats why if

you see a distinct layer that has a different shade which usually separated

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from the underlying layer, then its a masticatory mucosa. If you dont see

that, so its a lining mucosa.

Lip

It has three surfaces:

i. Oral Surface:

Inside

Non-keratinized

Lamina Properia

contains Seromucous minor salivary glands

Sub-mucousa contains a muscle, which is Orbicularis Oris

ii.Vermilion Zone

Between (junction) oral mucosa & skin

The Area used in cosmetics in females

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Specialized keratinized mucosa different from both skin & oral

mucosa Human feature, because it isnt found in animals.Animals have direct junction between skin & oral mucosa

Responsible for esthetics

Lacks hair follicles or glandular tissue

Sebaceous glands (glands that secrete wax material) may be

present at angles of the mouth and they arent associated with

hair follicles (Fordyces spot)

Red in color (human characteristics), because of thin

epithelium, we have a material

called Eleidin (transparent), thats

why it reflects the color of blood

vessels so it appears red, rich

blood vessels near the surface

(because of long papillae)

Its an intermediate zone

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Junctional region with oral surface

Parakeratinized (we should see the nuclei of the cells), note: if

the nuclei is lost, its considered as Orthokeratinized

iii. Skin Surface

Which is outside

We can find on skin appendages: Sweat glands, Erector pili

muscles, Hair follicles, Sebaceous glands

We can find on subcutaneous layer: Orbicularis Oris muscle

Skin is always keratinized, except in newly born babies (palms

of hands & soles of feet)

Fordyces Spot

when a sebaceous gland isnt associated with hair follicles, its called

Fordyces spot.

Are ectopic sebaceous glands

We find them at the corner of the mouth, at

the vermilion zone, Buccal mucosa & soft

palate,

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It tend to be more in

people with dark skin color.

Soft Palate

The epithelium is pink in color and its not keratinized

The lamina Propria is highly vascularized

Submucousa contains muscles (Tensor Veli Palateni, Levator Veli

Palateni, Palatoglossus, palatopharyngeous.)

We have minor salivary glands as well (mucus), on the oral surface of

the soft palate

Cheeks

The epithelium is non-keratinized

Lamina Propria is prisoned

Submucousa contains: fat cells, minor salivary glands (seromucus)

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It is Impossible to find hair follicles in the mouth.

we have to know each structure that exists in each of these tissues.

Why?? For example: when you know that fat cells arent located in the soft

palate, and you see a swelling there (tumor), you immediately exclude

Lipomaand thats because fat cells arent present, but when you see a

swelling (tumor) in the cheek, you cant exclude Lipoma, because fat cells are

there.


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It contains a muscle which is: Buccinator muscle

Ventral surface of the tongue


We have lamina propria

We have a submucousa that contains

connective tissue & muscle fibers mixed

together, thats why its difficult to

separate the epithelium from the underlying muscle

Floor of the mouth


We have lamina propria

Submucousa contains: minor salivary glands & major salivary glands

(Sub-Lingual gland & Sub-Mandibular gland, both are supplied

parasympathetically by the facial nerve VII through chorda tympani)

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The membrane is loosely attached, because we want the tongue to

move; if its fixed you wont be able to move your tongue freely, and

for the tongue to move, the floor of the mouth has to be very soft

Alveolar mucosa

which is the mucousa covering the sides of the bone below the gums.

Non-keratinized epithelium, although its supported by bone, but its

not keratinized because its not in contact with food

Lamina Propria: contains Dermal papillae which are short and thick,

and we have numerous elastic fibers to give the elasticity for that

tissue. Why we need it elastic? Because when you move your mouth

while mastication, the labial vestibule moves up and down, so you

need some elasticity

Submucousa which is loose and may contain seromucous glands

We have periosteum & bone

Vestibular fornix and frena

Why do we find a line between Gingivae and Alveolar mucosa? Because

Gingivae are keratinized; so they well appear whiter in color, while Alveolar

mucosa isnt, and thats why the junction between keratinized and non-keratinized tissues always appears very distinct.

The lips here are attached to the bone by a fold of mucus membrane, which

is called labial frenum. We have one frenum in the upper lip and one in

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the lower lip, and for the buccal mucosa we

have buccal frenum, so if you open your

mouth you will find labial frena, and if you go

posteriorly opposing premolars you will find

one or two buccal frena.

So these are folds of mucus membrane, they

contain connective tissue and no muscles.

The knowledge of these frena is very important, because if a patient is

provided with a denture usually the margins of the denture will cover this

area, and if you dont pay attention to these frena, when the patient moves

his lips or cheek the denture will drop down, so you have to give a space

for these tissues.

Masticatory Mucosa

Located in the Gingiva & Hard

palate

In the picture below the top layer is

different and we can find a nuclei,

so this is a parakeratinized

masticatory epithelium

Attachment Of Cells epithelium to connective tissue

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Usually in epithelium via desmosomes

We have attachment between the epithelium to lamina propria

through the basal lamina, this is an example of a basal cell attached

to another basal cell, at first you have to think of a way to attach

these cells to the basement membrane, so we have to use a

hemidesmosome between a cell

and a basement membrane, if its

cell to cell then we use

desmosome

Anchoring fibrils rope like which are attached to collagen fibers

Gingiva

Gingiva and the area surrounding the tooth develops from the

junction between the oral epithelium and reduced enamel epithelium

Develops from coalescence of reduced enamel epithelium & oral

epithelium, we said that fusing of tissues surrounding the tooth before

eruption with the oral mucosa is important for the eruption/emergence

of the tooth, and we said all the reduced enamel epithelium, which is

composed of exhausted cells, they are all lost except the area thats

covering the cervical margin of enamel, which is called the junctional

epithelium

We can see free zones:

*The free gingiva: its not attached (marginal gingiva)

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*The attached gingiva: its attached to the alveolar bone

*Interdental gingiva: between the teeth

The junction between the free gingiva and the attached gingiva iscalled the freegingival groove, and the junction between the

attached gingiva and the alveolar mucosa is called the muco-

gingival junction

Muco-gingival junction can be seen easily (very distinct), because it

reflects a junction between a keratinized tissue and a non-keratinized

tissue

Because the free gingiva is free, there will be a space between the

gingiva and the tooth, and its called gingival sulcus, and this is a

problem by the way, because this sulcus can be filled with food

causing gingivitis, thats why we always need to clean our teeth. So it

has two surfaces, one from outside called Oral Surface, and one

opposing the sulcus between the tooth and the gingiva called

Sulcular Surface

The oral surface of free gingiva is smooth and keratinized, but the

sulcular surface isnt keratinized, why? Because the sulcular surface

isnt in friction with food

If you continue down the sulcular surface

of the gingiva, you will see a tissue

connected to the tooth, its thejunctional

epithelium, which is an epithelium attached

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to enamel, and we said its the remnant of the reduced enamel

epithelium, and they are very exhausted cells (very week cells), thats

way microorganisms can invade this tissue inducing gingivitis

Its very easy to see the keratinized layer in the oral surface, and it

doesnt contain nuclei, so its orthokeratinized(sometimes we can

find parakeratinization at the gingiva)

The surface of the attached gingiva is stippled (has dots, like the

surface of an orange), and this is a sign of a healthy gingiva. When a

gingiva is swollen as a result of inflammation, stippling is lost

Loss of stippling is a sign of gingivitis

No submucosa is present in the attached gingiva, for that reason, no

salivary glands or minor salivary glands can exist at the gingiva(impossible)

We have periosteum and bone because attached gingiva is attached

to bone

Junctional epithelium

Its the area that connects the tooth to the gingiva, and its attached to

provide protection against anything that comes and cause gingivitis. Thats

why we need an epithelium attached to enamel to prevent anything coming

down and reaching the deep surfaces.

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The cells are very different:

Desmosomes are fewer and they are exhausted cells (remnant of

enamel organ), thats why

they are week

High rate of turnover

High metabolic activity

Stratum Germinativum: is

attached by

hemidesmosomes to the

lamina propria

Notice that the top surface cells, they have the function of being attached to

enamel, thats why the surface cells are non-keratinized.

Interdental Gingiva(interdental papilla)

Its the area between two teeth; it has facial and lingual portions. Now

between the facial and the lingual portions we have an epithelium called:

Col epithelium, its located exactly below the contact areas, and tends to be

bigger in posterior teeth. Because Col epithelium is protected by the

contact area and its not in contact with food, its usually non-keratinized

and concave in shape.

What happens in gingival resection?

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When the gingivae recede, exposing more of the tooth, we lose the two

papillae, becoming one papilla.

Hard palate

Keratinized epithelium

The lamina propria is dense under the rogue area. The rogue area

are the ridges that are found under the anterior part of the palate (you

can touch it with your tongue, just behind the gingiva of the upper

incisors)

Submucosa contains fat cells in the anterior area, glands in theposterior area, and in the midline there is no submucosa (thats why if

you see a tumor at the anterior region of the palate, its very rare for

this tumor to be glandular and more common to be lipoma, and vice

versa)

No tumors at the midline because of the absence of the submucosa

Rogue have a very important function in mastication, when we eat we

press food between this area and the tongue, and it has an important

function in phonetics (speech)

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Rogue are attached firmly to the bone by the means of traction bands

(bundles of collagen from bony palate to the papillae of the lamina

propria) and they function in anchorage

Specialized gustatory mucosa

Located in the dorsum of the tongue and we have four different types:

*Filiform papillae: found on all areas of surface of the tongue

(dorsum of the tongue), they are the white hair-like projections,

central cores of lamina propria covered by Ortho or

parakeratinized epithelium, dont have taste buds

*Fungiform papillae: the red spots between the filiform papillae

(exists only on the anterior 2/3 of the tongue), mushroom-shaped,

vascular core of lamina propria covered by keratinized or non-

keratinized epithelium, have taste buds on the surface

supplied by the facial nerve VII

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*Circumvallate papillae: located anterior to the sulcus terminalis,

although they belong embryologically to the posterior 1/3 of the

tongue, it has trenches; at the side of these trenches you will find

taste buds, because of the that, saliva pass there inducing taste,

and if you want to taste something else, you have to expel fluids

existing in these trenches, so you have to have a mechanism of

secreting salivary gland(watery secretion) to wash out old taste

and make the area ready to receive new taste (these salivary

glands are called von ebner glands) have taste buds at their

sides supplied by glossopharyngeal nerve IX

*Foliate papillae: at the side of the posterior 1/3 of the tongue,

have one or two longitudinal clefts, tastes buds found within the

non-keratinized parts, its underlined by a lymphatic tissue (lingual

tonsils) at the base of the tongue. Now some people have irregular

lower posterior teeth, each time the tongue moves, foliate papillae

comes in contact with this irregularity, inducing the lymphatictissue below causing a condition known as foliate papillitis(not the

foliate thats inflamed, but the lymphatic tissue underlying it lingual

tonsils ) have taste buds supplied by glossopharyngeal

nerve IX

Please remember that chorda tympani of facial nerve VII is related to

fungiform papillae taste buds, glossopharyngeal nerve IX is related tocircumvallate & foliate papillae, vagus nerve X is related to taste buds

present on the epiglottis & the larynx.

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And remember that the epithelium is avascular, thats why for epithelium to

receive the nutrients, it has to depend on the underlying lamina propria, and

for this reason epithelium has to have rite ridges, because we want blood

vessels in the papillae to reach all the areas of the epithelium. If you

provide epithelium with vascularization (which is impossible) you will find

the junction is straight, but this epithelium has to be in intimate relation with

the lamina propria to receive blood from it.

The End

Done by:

Sundos Abu Zaid

Khalid Mortaja

Asil Elluazi

Documents

Oral Histo 10th Lec