25. Oral Mucosa Flashcards
The oral mucosa forms a continuum with … and …
gingiva
tooth attachment tissues
Oral mucosa lines …
the whole oral cavity
How does the oral mucosa develop in the oral cavity?
- lining of the oral cavity (oral epithelium) and external lining of body (epidermis) are both derived from embryonic ectoderm and form a continuum
- similar but different morph features - ectodermal appendages
- similar but diff genetic regulation of development, differentiation and maintenance
Define ‘oral vestibule’
slit-like space between lips/cheeks and alveolar bone/teeth
Prominent frena can affect …
stability of dentures
A large labial frenulum with attachment site near the alvrolar crest can cause …
a midline diastema between the maxillary central incisors
- the gap
Functions of oral mucosa
- mechanical protection (masticatory forces - compression, stretching, shearing, abrasion)
- barrier to microorganisms and toxins
- immunological defence (immediate and adaptive)
- lubrication and buffering (saliva from minor glands)
- sensation (touch, pain, taste, proprioreception)
Define ‘functional adaptation’ in relation to oral mucosa
- different parts of oral mucosa must adapt morphologically to perform specific functions
List regional variations of oral mucosa and their adaptations
- epithelial thickness
- degree of keratinisation
- interface with connective tissue
- composition of connective tissue
- presence or absence of a submucosa
Perentage distribution of mucosa types
- lining mucosa - 60%
- masticatory - 25%
- specialised - 15%
Compare the layers of oral mucosa to the layers in skin
- oral epithelium vs epidermis
- lamina propria vs dermis
- submucosa vs hypodermis
Explain composition of oral epithelium/epidermis
- stratified squamous epithelium
- epithelial ridges (rete or pegs)
- keratinocytes (cell layers, express keratin proteins)
Components of lamina propria/dermis
- papillae
- fibroblasts, macrophages, lymphocytes, collagen (I, III), elastic fibres
- blood vessels and nerves
Composition of submucosa/hypodermis
- loose connective tissue
- fibroblasts
- larger blood vessels/nerves
- fat deposits
- salivary glands
Where is submucosa found?
- cheeks
- lips
- lateral palate
Basic tissue architecture of oral mucosa and skin is similar but …
- no hair follicles
- no sweat glands
Compare the submucosa and the mucoperiosteum
- submucosa provides mobility and acts as a cushion (e.g in lining mucosa)
- in mucoperiosteum, lamina propria is more fibrous and directly joined with periosteum of bone - e.g masticatory mucosa (middle of hard palate, gingiva)
List layers of the stratified epithelium of oral mucosa from outside in
- keratinised layer/stratum corneum
- granular layer (stratum granulosum)
- prickle (Suprabasal) cell layer
- basal cell layer (stratum basale)
Explain keratinised layer of stratified squamous epithelium
- very flat cells
- around 20 cell layers
- cornified (dead)
- no cell organelles including nucleus
- filaggrin binds to keratin filaments together (keratin)
- crosslinking of involucrin, cornified envelope - barrier, cell shedding (desquamation)
Explain granular layer of stratified squamous epithelium
- larger, flatter cells
- several layers
- maturating
- loss of cell organelles and cytoplasm filled with keratohyaline granules (contains profilaggrin and lipids)
Explain Prickle (suprabasal) cell layer/stratum spinosum of stratified squamous epithelium
- round ‘spiny’ cells (increase in desmosomes)
- several layers
- differentiating
- only parabasal cells can proliferate
- expresses keratins 1 and 10 (loricrin and involucrin)
Explain basal cell layer/stratum basale of stratified squamous epithelium
- cuboidal cells
- proliferating
- single cell layer
- basal lamina attached to lamina propria
- contains stem cells and transmit-amplifying cells (regeneration)
- expresses keratins 5 (type II Basic) and 14 (Type 1, Acidic)
3 types of keratinisation
- orthokeratinised
- parakeratinised
- nonkeratinised
What does orthokeratinised mean?
- cornified layer (dead cells)
- no cell nuclei
- hard palate, tongue
What does parakeratinised mean?
- cornified layer (dead cells)
- cell nuclei present
- gingiva
What does nonkeratinised mean?
- superficial layer (live cells)
- no keratohyalin granules
- lining mucosa
Regeneration cycle of stratified squamous epithelium
- skin - 27 days
- oral mucosa 9-14 days
- 2-3 times faster in oral
List other cells/’clear cells’ in oral mucosa
- melanocytes
- Merkel cells
- Langerhams cells
- Lymphocytes
What do melanocytes do?
- basal
- produce melanin pigment and transfer it to keratinocytes via dendritic processes
Role of Merkel cells
- basal
- sensory receptor cells - sense light touch
Role of Langerhans cells
- suprabasal
- dendritic cells
- antigen processing and presenting
Role of lymphocytes
- in inflammatory response
- often associated with Langerhans cells
Define ‘incisive papilla’
- prominence overlying nasopalatine foramen
- important in denture fitting
Define ‘palatine raphe’
- midline epithelial ridge
- directly attached to bone
Define ‘palatine rugae’
unique epithelial folds for food transport to pharynx