OCB02-2023 Structure & function of the oral mucosa

Question 1

What are the anterior and posterior boundaries of the oral mucosa?

Answer 1

Anterior boundary is the mammalian border of the lips

Posteriorly it ends at the palatoglossal fold

Question 2

What does the oral mucosa comprise of?

Answer 2

Upper and lower labial mucosa
Upper and lower labial sulcus
Free and attached gingiva
Buccal sulcus
Buccal mucosa
Hard palate
Soft palate
Dorsum of the tongue
Ventral surface of the tongue 
Floor of the mouth

Question 3

What is oral mucosa?

Answer 3

The mucous membrane lining the inside of the mouth

It consists of stratified squamous epithelium and lamina propria

Question 4

What epithelium is oral epithelium?

Answer 4

stratified squamous epithelium

Question 5

What are the main components of oral mucosa?

Answer 5

Oral epithelium

Lamina propria

Question 6

What is the boundary between mucosa and submucosa called in the gut?

Answer 6

muscularis mucosa

Question 7

What boundary is blurred in oral cavity?

Answer 7

The boundary between submucosa and mucosa

Question 8

How do you know when you are in submucosa in the oral cavity?

Answer 8

Fat and skeletal muscle is present in submucosa

Question 9

What does the lamina propria contain?

Answer 9

Fibrous tissue and blood vessels

Question 10

What are the downward projections in epithelium called?

Answer 10

Rete processes

Question 11

What are upward projections in epithelium called?

Answer 11

Connective tissue papillae

Question 12

What are the 3 types of mucosa?

Answer 12

Masticatory
Lining
Specialised

Question 13

Where is masticatory mucosa present?

Answer 13

Hard palate and gingiva

Question 14

Where is lining mucosa present?

Answer 14

Buccal mucosa
Buccal sulcus
Labial mucosa
Ventral tongue
Floor of mouth

Question 15

Where is specialised mucosa present?

Answer 15

Dorsal tongue

Question 16

Where is the thickest epithelium present?

Answer 16

Buccal mucosa

Question 17

Where is the lamina propria thickest?

Answer 17

Hard palate

Question 18

What is the structure of mucosa in the floor of the mouth like?

Answer 18

Epithelium is thin and lacks rete processes

Lamina propria is thin

Question 19

Why is the lamina propria thin in the floor of the mouth?

Answer 19

Due to the presence of salivary glands

Question 20

How is masticatory mucosa adapted to withstand shear forces?

Answer 20

The pattern of rete processes are longer so form a greater area of surface contact with the underlying lamina propria

Question 21

What is mucoperiosteum?

Answer 21

In the gingiva and parts of hard palate, the oral mucosa lies continuous with the periosteum without any intervening submucosa

Question 22

What is a major difference between lining and masticatory mucosa?

Answer 22

There is a sub mucosal layer in lining mucosa that consists of fat, skeletal muscle and minor salivary glands
There is no definite submucosal layer in masticatory mucosa, the lamina propria continues to the periosteum of the alveolar ridges or hard palate

Question 23

Why is raising a mucosal flap in the gingiva or hard palate difficult?

Answer 23

The lamina propria is tightly bound to the underlying bone

Question 24

Why is the term ‘mucoperiosteum’ used?

Answer 24

There is no definite submucosal layer in masticatory mucosa

Question 25

Is masticatory mucosa keratinised or non-keratinised?

Answer 25

keratinised

Question 26

What are the 4 layers of masticatory mucosa?

Answer 26

``` Stratum basale (basal layer) Stratum spinosum (prickle cell layer) Stratum granulosum (granular layer) Stratum corner (keratinised layer) ```

Question 27

What are the two functional populations of the oral epithelium?

Answer 27

Progenitor population | Maturing population

Question 28

Where does proliferation occur in oral epithelium?

Answer 28

In the basal cell layer and immediate supra basal

Question 29

Where does maturation occur in the oral epithelium?

Answer 29

From the prickle cell layer upwards towards the surface

Question 30

What does the basal compartment consist of?

Answer 30

Stem cells and amplifying cells

Question 31

What happens when the stem cell divides in the basal compartment?

Answer 31

As the stem cell divides, one cell remains as a stem cell and the other forms a transit amplifying cell that matures up the layers of epithelium

Question 32

What is a mitotic abnormality within epithelium?

Answer 32

Mitotic figures found in the prickle cell layer

Question 33

What is bullous pemphigoid antigen?

Answer 33

Helps anchor the basal cell to the underlying basal lamina

Question 34

What is the basal lamina?

Answer 34

The interface between the oral epithelium and lamina propria

Question 35

What is pemphigoid?

Answer 35

A blistering disease characterised by autoantibodies to the bulls pemphigoid antigen

Question 36

How are basal cells attached to the basal zone?

Answer 36

Via hemidesmosomes

Question 37

What is mucus membrane pemphigoid?

Answer 37

Patient's immune system manufactures antibodies against bullous pemphigoid antigen and so weakening the adhesion between the epithelium with lamina propria There is a lack of function of the antigen so there is a split form basal cells to the lamina propria Causes blistering

Question 38

What occurs when patients develop antibodies to desmoglein?

Answer 38

There is a breakdown of desmosomes in the prickle cell layer, resulting in breakdown of inter-cellular cohesion Gaps appear in the prickly cell layer resulting in blisters

Question 39

What is the difference between intra-epithelial blisters and pemphigoid?

Answer 39

Pemphigoid occurs sub-epithelially so intraepithelial blisters are more fragile and breakdown more easily

Question 40

How do cells differ when they progress from the prickle cell layer to stratum granulosum?

Answer 40

Cells become flattened Nuceli elongate Lose a lot of nuclei

Question 41

What are the purpose of keratohyalin granules in stratum granulosum?

Answer 41

They release filagrin precursors which aggregates keratin resulting in flattening of keratinocytes

Question 42

What is the purpose of the cornified layer?

Answer 42

Provides structural integrity | Waterproof

Question 43

How does structure change as the basal layer progresses to the cornfield layer?

Answer 43

Becomes terminally differentiated Loses organelles like nuclei Nuclei become less pronounced

Question 44

In a histological stain, what do white and pink areas represent?

Answer 44

White- hyperkeratinisation | Pink- parakeratinisation

Question 45

Is lining mucosa keratinised or non-keratinised?

Answer 45

Non-keratinised

Question 46

Why is there no stratum granulosum in lining mucosa? What is this layer called instead?

Answer 46

It is non-keratinised epithelium | Stratum intermedium

Question 47

Why is there no cornified layer in lining mucosa? What is this layer called instead?

Answer 47

No keratin | The superficial layer

Question 48

How does the function of lining mucosa differ from masticatory without cornfield envelope and keratin?

Answer 48

More flexible and less waterproof

Question 49

What is the vermillion zone?

Answer 49

The border between oral mucosa and skin on the lip

Question 50

What structures does the lower lip lack?

Answer 50

Skin adnexae | Salivary glands

Question 51

Where is specialised mucosa found?

Answer 51

Dorsally on the tongue, specifically in the region of the taste buds on lingual papillae

Question 52

What are the non-keratinocytes present within the oral epithelium?

Answer 52

Melanocytes Langerhan cells Merkel cells Lymphocytes

Question 53

What is present at the base of the tongue?

Answer 53

Crypts that extend down as invaginations into the surface of the mucosa

Question 54

What is the epithelium lining crypts called?

Answer 54

Reticulated crypt epithelium

Question 55

What are characteristics of the epithelium lining crypts?

Answer 55

More loosely capped, non-keratinised and contains lymphocytes

Question 56

Why does the epithelium of crypts need to be loose?

Answer 56

To allows for antigens to pass through the epithelium