oral mucosa 1

What is oral mucosa?

consists of epithelium and connective tissue (lamina propria) and it is the lining of the oral cavity

Between which two body tissues is the oral mucosa considered a transitional zone?

Between the skin and the gastrointestinal tract (GIT).

Why is oral mucosa called a transitional tissue?

Because it has structural and functional characteristics of both the skin and the GIT.

In what way is oral mucosa similar to the gastrointestinal tract?

It is bathed in fluid and has a high rate of cell turnover.

In what way is oral mucosa similar to the skin?

It has a stratified epithelium, which is keratinized in many areas.

What is the function of keratinization in oral mucosa?

It protects the tissue and limits diffusion across the mucosa.

What are the major layers of oral mucosa?

1. Epithelium

2. Lamina propria

3. Submucosa (where present)

Which layer lies directly beneath the epithelium?

lamina propria, which contains blood vessels and connective tissue fibers?

What lies beneath the submucosa in attached areas?

the periosteum covering the bone.

Which layer provides the protective surface of the oral cavity?

epithelium

what are some features of the oral mucosa?

• moist

• salivary glands

• no hair follicles

• less firm

• more smooth

• deeply colored

what are some features of the skin?

• not moist

• sebaceous

• contains hair follicle

• more firm

• less smooth

• less color

what are the general features of epithelial tissue?

1. cells rests on basement membrane & have a free surface

2. cells adhere to each other in one layer or more.

3. cells are avascular but have nerve fibers.

4. cells cover surfaces, line cavities and form glands.

5. basal surface contact the basement membrane while free surface interface with external environment or space within the body.

what are the 2 main components of the oral mucosa?

1. stratified squamous epithelium (oral epithelium)

2. underlying connective tissue layer (lamina propria)

what is the rete-pegs?

downward projections of oral epithelium that interdigitate with connective tissue papilla

what are the connective tissue papillae?

upward projections of connective tissue that interlock with rete pegs.

what are the functions of the oral epithelium?

1. protection

2. sensation

3. secretion

protective function of oral epithelium

• Separates deeper tissues from the oral environment.

• Resists masticatory forces.

• Acts as a barrier against microorganisms and toxins.

sensation function of oral epithelium

it detects temperature, touch, pain, taste, and thirst.

• mouth receptors respond to temperature, touch, pain taste and thirst

• tongue has tastebuds

• reflexes (swallowing, salivation and gagging) are initiated by receptors in the oral cavity

What is the major secretion associated with oral mucosa?

Saliva from major and minor salivary glands.

Why is saliva important?

it keeps the oral mucosa moist and lubricated.

how is the oral mucosa classified?

1. outer vestibule

2. oral cavity proper

What bounds the vestibule?

lips and cheeks.

What forms the roof of the oral cavity proper?

Hard and soft palate.

What forms the floor of the oral cavity?

Floor of the mouth and tongue.

How is oral mucosa classified?

• 25% Masticatory mucosa

• 60% Lining mucosa

• 15% Specialized mucosa

what does the masticatory mucosa consist of?

composing 25% of the oral mucosa, it is the part that is subjected to the force of mastication and pressure. its parts are:

1. gingiva

2. hard palate

What type of epithelium covers masticatory mucosa?

Keratinized or parakeratinized stratified squamous epithelium.

what is the lining mucosa?

consisting of 60% of the oral mucosa, it is present in areas which are not subjected to high force but it must remain mobile and distensible.

Where is lining mucosa found?

• Buccal mucosa

• Labial mucosa

• Alveolar mucosa

• Floor of the mouth

• Ventral tongue

• Soft palate

What type of epithelium covers lining mucosa?

Non-keratinized stratified squamous epithelium.

Where is specialized mucosa located?

On the dorsal surface of the tongue.

what is the specialized mucosa?

mucosa covering the dorsal surface of the tongue. it contains different types of taste buds, papillae and lingual tonsils and lymph tissues

What is the embryological origin of oral epithelium?

Ectoderm

What are the four layers of keratinized epithelium?

• Basal

• Spinous (Prickle)

• Granular

• Cornified

What are the four layers of non-keratinized epithelium?

• Basal

• Spinous

• Intermediate

• Superficial

Which layers are absent in non-keratinized epithelium?

Granular and cornified layers.

Where is keratinized epithelium found?

Gingiva and hard palate, as they are areas subjected to masticatory forces

What are keratin-producing cells called?

Keratinocytes (keratocytes).

what is the basal layer?

a single row of columnar or cuboidal cells that are closely attached to each other and are arranged on the basement membrane

what do the basal layer cells possess?

all the usual organelles & tonofilaments

what are tonofilaments?

cytokeratin protein filaments synthesized by ribosomes.

which layer is responsible for mitosis?

basal layer, since it consists of two cells: progenitor and maturative cells

What are progenitor cells?

Cells that remain in the basal layer and continue dividing.

What are maturative cells?

Cells that migrate toward the epithelial surface.

what is the spinous cell layer?

also known as the prickle cell layer, it consists of several rows of polyhedral cells of different shapes and sizes. it has numerous well developed organelles. it has a wide inter cellular space compared to non keratinized epithelium. there is no sudden change appearance of cells and there is a gradual decrease in synthetic activity throughout this layer

Which two layers make up more than half of the epithelial thickness?

Basal and spinous layers.

Why is it called the prickle layer?

Because intercellular bridges give the cells a prickly appearance.

Which epithelial layer has the greatest protein synthesis?

Spinous layer.

What are Odland bodies?

Membrane-coating granules (keratinosomes) derived from the Golgi apparatus that are present in the upper part of spinous layer

What is the function of Odland bodies?

• Form a permeability barrier.

• Thicken the cell membrane.

what is the granular layer?

it is several rows of flattened epithelial cells. many of its organelles are reduced, and the cytoplasm is occupied by tonofilaments and tonofibrilis

what do the cells of granular layer contain?

a large number of small granules known as keratohyalin granules, which contribute to keratin formation.

what do Odlands body do in the granular cell layer?

discharge into inter-cellular space which act as barrier & increase the thickness of epith.

what is the cornified layer?

present in the keratinized epithelium as the final stage of maturation.

what happens to the cells in the cornified layer?

• Lose nuclei and organelles.

• Become filled with keratin.

What is desquamation?

Shedding of superficial keratinized cells.

Why are desmosomes weak in the cornified layer?

To allow desquamation.

What is the main function of the cornified layer?

Mechanical and chemical protection.

how does the nonkeratinized epithelium differ from the keratinized epithelium?

It lacks granular and cornified layers.

What are the outer layers of non-keratinized epithelium?

Intermediate and superficial layers.

What accumulates in cells of the intermediate layer?

Glycogen

How are intercellular spaces in non-keratinized epithelium?

Very small because cells are tightly packed.

Do superficial cells of non-keratinized epithelium retain nuclei?

Yes, they retain nuclei and a few organelles.

Does the intermediate layer contain Odland bodies?

Yes, but they differ in size, shape, and location from those in keratinized epithelium.