Oral Histology - Oral Mucosa

Mucous membrane

describes the moist lining of the GI tract, nasal passages, other body cavities that communicate with the exterior

In the oral cavity, the mucous membrane is often called the

oral mucous membrane or oral mucosa

At the ____, the oral mucosa is continuous with the skin

lips

At the _____, the oral mucosa is continuous with the mucosa lining the rest of the gut

pharynx

The oral mucosa is located anatomically between _____ and _____________ _______ and shows some properties of each

skin, gastrointestinal mucosa

The skin, oral mucosa, and intestinal lining consist of two separate tissue components:

covering epithelium and underlying connective tissue

Functions of the oral mucosa

- protection

- sensation

- secretion

- thermal regulation

protective functions of oral mucosa

- barrier for mechanical trauma and microbiological insults

- normal biting and chewing activities expose soft tissue to mechanical forces and surface abrasions

- there are a number of adaptations of the epithelium and CT to withstand insults

- epithelium of the oral mucosa is a major barrier to the toxic effect of microorganisms on tissues

- epithelial homeostasis

epithelial homeostasis

- cell production in the deeper layers will be balanced by loss of cells from the surface

- rate at which cells leave the surface represents a defense mechanism by rapidly clearing the substrate to which many microorganisms adhere

- this way they are unable to produce toxic effects or invade

mechanical forces include the actions of

- compression

- stretching

- shearing

surface abrasions may be described as

hard particles in the diet

sensation function of oral mucosa

- temperature (heat, cold)

- touch, pain

- taste buds

- thirst

- reflexes

reflexes include

- swallowing

- gagging

- retching

- salivating

secretion function of oral mucosa

- saliva produced by salivary glands contributes to the maintenance of a moist surface

- distant from the mucosa, secretions pass through long ducts

- minor salivary glands are associated with the oral mucosa

- sebaceous glands frequently present in the oral mucosa but secretions are mostly insignificant

thermal regulation function of oral mucosa

- practically no role

- no obvious specializations of blood vessels for controlling heat transfer

- important in animals via panting

Types of Oral Epithelium

- ortho-keratinization

- parakeratinization

- non-keratinization

ortho-keratinization

- shows narrow, darkly staining granular layer in gingiva

- gingiva, hard palate, some areas of dorsal tongue

parakeratinization

- in gingiva, shows keratin squames that have retained pyknotic nuclei

- granular layer containing only a few scattered granules

non-keratinization

- in buccal mucosa, shows no clear distinction between cell strata

- nuclei are apparent in the surface layers

- note thickness and epithelial ridge patterns, patterns of maturation

- no granular layer

keratinization of non-keratinized buccal epithelium may result from

irritation by tobacco use

keratinization of normal hard palate

This image depicts

Hyperkaratosis in the hard palate may occur as a result of

irritation by smoking

basal cell layer of keratinized epithelium

- cuboidal or columnar cells containing bundles of tonofibrils and other cell organelles

- site of most cell divisions

prickle/spinosum cell layer of keratinized epithelium

- larger ovoid cells containing conspicuous tonofibril bundles

- membrane coating granules appear in upper part of this layer

granular cell layer of keratinized epithelium

- flattened cells containing conspicuous keratohyaline granules associated with tonofibrils

- membrane coating granules fuse with cell membrane in upper part

- internal membrane thickening occurs

keratinized cell layer of keratinized epithelium

- extremely flattened and dehydrated cells in which all organelles have been lost

- cell filled only with packed fibrillar material

- when pyknotic nuclei are retained

- parakeratinization occurs

basal cell layer of nonkeratinized epithelium

- cuboidal or columnar cells containing separate tonofilaments and other cell organelles

- site of most cell divisions

prickle/spinosum layer of nonkeratinized epithelium

- larger ovoid cells containing dispersed tonofilaments

- membrane coating granules appear in upper part of layer

- filaments become numerous

intermediate cell layer of nonkeratinized epithelium

slightly flattened cells containing many dispersed tonofilaments and glycogen

superficial cell layer of nonkeratinized epithelium

- slightly flattened cells with dispersed filaments and glycogen

- fewer organelles present, but nuclei persist

2 parts of the oral cavity

- outer vestibule

- oral cavity proper

outer vestibule is bounded by

lips and cheeks

oral cavity proper includes

superior zone: hard and soft palates

inferior border: floor of the mouth and base of the tongue

posteriorly the oral cavity proper is bounded by

pillars of the fauces and tonsils

the oral mucosa shows considerable __________ __________ in different regions of the oral cavity, but 3 main types can be identified according to their primary function: __________, ________, ___________ mucosa

structural variation, masticatory, lining, specialized

the larger part of the oral mucosa is represented with _______ mucosa, amounting to ___% of the total area

lining, 60

masticatory mucosa takes up around ___% of the oral mucosa

25

specialized mucosa occupies smaller areas, totaling around ___% of the oral mucosa

15

the oral mucosa varies considerably in ___________ and ________

firmness, texture

the lining mucosa of the lips and cheeks is

soft and pliable

the gingiva and hard palate are covered by a layer that is

firm and immobile

the differences in firmness and texture are clinically important for

- giving local injections of anesthetics

- taking biopsies of oral mucosa

fluid can be introduced easily into the ________ _______ mucosa

loose lining

injection into the __________ mucosa is difficult and painful

masticatory

the lining mucosa ______ when incised and may require suturing

gapes

masticatory mucosa (does/does not) gape

does not

the accumulation of fluid with inflammation is obvious and painful in

masticatory mucosa

in lining mucosa, fluid ___________ and ___________ may not be as painful

disperses, inflammation

lining mucosa (60%) covers

- floor of mouth

- ventral tongue

- alveolar mucosa

- cheeks

- lips

- soft palate

because the lining mucosa does not function in mastication, it has

minimal attrition

masticatory mucosa (25%) covers

- free, attached, interdental gingiva

- hard palate

masticatory mucosa is the ________ mucosa that comes in contact with food during ______________

primary, mastication

gingiva has ___% parakeratinized, ___% ortho-keratinized, and ___% nonkeratinized regions

75, 15, 10

specialized mucosa (15%) covers

- dorsal side of tongue

- mostly keratinized epithelial papillae

the oral mucosa can be distinguished from skin due to its

- moist surface

- absence of most appendages like hair follicles, sweat glands, and nails

there are __________ glands near the ______ salivary glands

sebaceous, minor

sebaceous glands are present in the ___________ of the lip and ________ _______ and occasionally in the alveolar mucosa, tonsillar pillar, and dorsum of the tongue

vermillion, buccal mucosa

sebaceous glands produce a _______ secretion called _______, the function of which is unclear

fatty, sebum

some claim that sebum may ___________ the surface of mucosa so it can slide easily against the teeth

lubricate

clinically, sebaceous glands appear as clusters of _____________ spots called _________ granules

pale-yellowish, Fordyce's

healthy gingiva show surface ________, small indentations on the mucosal surface

stippling

in some, a slight whitish ridge occurs along the buccal mucosa in the occlusal plane of the teeth, known as the ______ _______, a keratinized region that may represent the effect of abrasion from rough tooth restorations or cheek biting

linea alba

the two main tissue components of the oral mucosa are

stratified squamous oral epithelium and connective tissue layer called the lamina propria

there is a basal lamina on the interface between _______ and ________

epithelium, connective tissue

in many regions, a layer of ________ _______ or _________ connective tissue separates the oral mucosa from underlying bone or muscle

loose fatty, glandular

the composition of glandular connective tissue determines the flexibility of the attachment of ________ _______ to _________ ______

oral mucosa, underlying structures

The interface between epithelium and connective tissue is usually irregular and upward projections called the ___________ _________ _________ which interdigitate with _________ _______/____

connective tissue papillae, epithelial ridges/pegs

in regions like the gingiva or parts of the hard palate, oral mucosa is attached _______ to the periosteum of underlying bone with no intervening ________________

directly, mucoperiosteum

with no intervening submucosa present, it provides a

firm, inelastic attachment

minor salivary glands are situated in the _______ of the mucosa, while sebaceous glands lie in the ________ _______

submucosa, lamina propria

in several regions of the oral cavity, there are ________ of lymphoid tissue that consist of _______ formed by invaginations of the epithelium into the lamina propria. These areas are infiltrated extensively by lymphocytes and plasma cells and mount immunologic reactions

nodules, crypts

the largest accumulations of lymphoid tissue are found in the __________ part of the oral cavity where they form the Waldeyer's ring

posterior

the Waldeyer's ring consists of

- lingual tonsils

- palatine tonsils

- pharyngeal tonsils

small lymphoid nodules also may occur sometimes in the mucosa of the ________ _______, ______ surface of the tongue, and ________ of the mouth

soft palate, ventral, floor

The progenitor cells are situated in the ______ ______ in thin epithelia and in the ______ two to three cell layers in thicker epithelia

basal layer, lower

The larger portion of the progenitor compartment is composed of dividing cells, the function of which is to

increase the number of cells available for subsequent maturation

Turnover time for skin

52 to 75 days

Turnover time for gut

4 to 14 days

Turnover time for gingiva

41to 57 days

Turnover time in the cheek

25 days

Regional differences in the patterns of epithelial maturation appear to be associated with ________ ________ _______; for example, non-keratinized buccal epithelium turns over ______ than keratinized gingival epithelium

different turnover rates, faster

Various cytokines (such as epidermal growth factor, keratinocyte growth factor, interleukin-1, and transforming growth factors α and β) and Vit D are known to __________ ____________ and ___________ of oral mucosa, skin, and many other tissues

regulate proliferation, differentiation

Because cancer chemotherapeutic drugs block mitotic division, a significant number of patients taking them develop ______ ______ and thus experience pain and difficulty in eating, drinking, and maintaining oral hygiene

oral ulcers

Keratinized

inflexible, tough, resistant to abrasion, and tightly bound to the lamina propria

keratinization is also called

cornification

the basal layer (stratum basale) is made of ______/______ cells adjacent to the basal lamina

cuboidal/columnar

above the basal layer in keratinized cells, there are several rows of

larger elliptical or spherical cells known as the prickle cell layer or stratum spinosum

basal and prickle cell layers constitute ___ to ___ thickness of the epithelium

1/2-2/3

the stratum granulosum consists of

larger, flattened cells containing small basophilic granules

basophilic granules are also called

keratohyalin granules

squames (do/do not) contain nuclei

do not

the surface layer of flat squamous cells is called

stratum corneum

the stratum corneum is sometimes called

cornified layer, horny layer

orthokeratinization

pattern of maturation of cells

parakeratinization

variation of keratinization

n parakeratinized epithelium, the surface layer stains for keratin, but _________ ________ are retained in many or all of the squames

shrunken (or pyknotic) nuclei

parakeratinization (is/is not) a normal event in oral epithelium and (does/does not) imply disease

is, does not

in the epidermis, parakeratinization (may be/may not be) associated with diseases like psoriasis

may

clear cells represent a variety of cell types including

melanocytes, Langerhans cells, Merkel cells, inflammatory cells

clear cells make up __% of the cell population of the oral epithelium

10