OCB02-2023 Flashcards
What are the anterior and posterior boundaries of the oral mucosa?
Anterior = vermillion border
Posterior = anterior pillar of fauces (palatoglossal arch)
What areas are covered by oral mucosae?
Upper and lower labial mucosa and sulci
Buccal sulci and mucosa
Free and attached gingiva
Hard and soft palate
Dorsal and ventral surface of tongue
Floor of mouth
What are the two main parts of the oral mucosa?
Epithelium
Lamina propria (corium)
How do you know where the submucosa of the oral mucosa is histologically?
Fat and skeletal muscle (and possibly minor salivary glands) present
What is the boundary between the mucosa and submucosa in the alimentary tract?
Muscularis mucosae
What are rete pegs?
Extensions of epithelium into lamina propria
What are connective tissue papillae?
Extensions of lamina propria between rete pegs
What is another term for masticatory mucosa?
Oral mucoperiosteum
What does the lining mucosa cover?
Buccal mucosa and sulci
Labial mucosa and sulci
Ventral tongue
Floor of mouth
Soft palate
Where can you find specialised mucosa in the mouth?
Dorsal aspect of anterior 2/3 of tongue and parts of lateral margin of tongue
Where is the epithelium of the oral mucosa thickest?
Buccal mucosa
Where are the rete pegs of the oral mucosa longest and most slender?
Hard palate
Where is the lamina propria thickest in the oral mucosa?
Hard palate
Why is the lamina propria thinner at the floor of the mouth?
Salivary glands
Which type of oral mucosa has no definite submucosa?
Masticatory mucosa/oral mucoperiosteum
Describe masticatory mucosa.
Covers hard palate and attached gingiva
No definite submucosa
Lamina propria continuous with periosteum of underlying bone (tightly bound)
What are the layers of epithelium in masticatory mucosa?
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum corneum
Describe the stratum basale of the masticatory mucosa.
Stem cells and transit amplifying cells
Single layer of short columnar/cuboidal, hyperchromatic cells
Attached to underlying lamina propria at basal lamina via hemidesmosomes
What stain can be used to view the basal lamina/basement membrane zone?
PAS (periodic acid- Schiff) stain
Also electron microscopy
Describe how the basement membrane zone.
Hemidesmosomes concentrate tonofilaments of basal cells and some traverse the membrane to attach to the basal lamina
Beneath basal lamina are anchoring fibrils of type VII collagen that loop between collagen fibrils of the lamina propria
Most proteins of BL made by epithelial cells
Bullous pemphigoid antigen helps anchor basal cell to BL
How does the basal lamina appear under electron microscopy?
2 layers = lamina lucida (superficial) and lamina densa (deep)
What is the function of the bullous pemphigoid antigen?
Helps anchor basal cells to basal lamina
What is mucous membrane pemphigoid?
Autoimmune condition with antibodies targeting bullous pemphigoid antigen of the basal lamina
Weakens adhesion between epithelium and lamina propria
Formation of vesicles, bullae and blisters
Describe the stratum spinosum of masticatory mucosa.
Larger cells than basal layer
Polygonal, pale-staining cells with large nuclei with nucleoli
Cells linked by desmosomes
In keratinised masticatory mucosa, which layer of the epithelium is thickest?
Stratum spinosum
Describe a desmosome.
Intercellular adhesion (attach adjacent cells together)
Formed of cadherins which are formed by desmoglein and desmocollin
What makes up a cadherin?
Desmoglein and desmocollin
What is pemphigus?
Autoimmune disease with antibodies targeting desmoglein of desmosomes
Breakdown of intercellular adhesion and cells pull away from each other (acantholysis)
Formation of blisters
What is acantholysis?
Loss of intercellular connections (desmosomes)
The blisters in which disease break more easily and why: pemphigoid or pemphigus?
Pemphigus
Blisters are more superficial
Describe the stratum granulosum of masticatory mucosa?
Keratohyaline (basophilic) granules in cytoplasm
Cells become flattened, nuclei become enlarged and elongated
Start to lose nuclei and organelles
What is keratohyaline the precursor for?
Filaggrin
Describe the stratum corneum of masticatory mucosa?
Stains bright orange-pink with H&E
Indistinguishable cells, flattened, tightly-packed with few organelles
What are the different forms of stratum corneum in the oral mucosa?
Parakeratinised = nuclei preserved
Orthokeratinised = nuclei lost
What is the function of filaggrin?
As the cells progress from the granular to cornified layer, filaggrin forms a tight complex with loricrin and involucrin
Envelopes bundles of keratin tonofilaments and merge with cell membrane of maturing cells to create the “cornified envelope”
For structural integrity and waterproofing
What colour does hyperkeratosis look?
White
Under normal circumstances, is the lining mucosa keratinised?
No (normally non-keratinised stratified squamous epithelium)
What are the layers of the lining mucosa epithelium?
Stratum basale
Stratum intermedium (no granules)
Stratum superficiale (no keratin)
Why is lining mucosa more flexible and less waterproof than masticatory mucosa?
No keratin or cornified envelope
Where may sebaceous glands be found in the oral cavity?
Lamina propria of buccal mucosa or labial mucosa
What are Fordyce spots/granules?
Benign yellowish small plaques formed by coalescing of sebaceous glands of buccal or labial mucosa
Why are the vermillion border and lips red?
Thin epithelium with many dilated blood vessels
What separates the base of the tongue from the oral tongue?
Sulcus terminalis
What is found anterior to the sulcus terminalis?
Circumvallate papillae in an inverted V-shape
Which papillae are most abundant on the tongue?
Filiform papillae
Which papillae are the least abundant on the tongue?
Foliate papillae
Describe filiform papillae.
Thread-like projections covered with keratinised stratified squamous epithelium
Usually parakeratinised
Each is supported on a fibrous tissue core (lamina propria)
Interspersed between zones of non-keratising stratified squamous epithelium
Aid in mastication
May have secondary papillae branching off
Describe fungiform papillae.
Round, smooth-looking, almost mushroom-like
Appear red due to highly vascularised lamina propria and thinner epithelium (than filiform)
Numerous tastebuds at surface
Describe circumvallate papillae.
Non-keratinising stratified squamous epithelium
Surrounded by a trench which has numerous tastebuds located along its wall
Many serous minor salivary glands (glands of Von Ebner) in submucosa essential for taste
What are the glands of Von Ebner?
Minor exocrine serous salivary glands found in submucosa adjacent to trenches of circumvallate and foliate papillae
Secrete lingual lipase
Innervated by glossopharyngeal nerve (C.IX)
Describe a tastebud briefly.
Rounded, modified nerve structures with pores opening onto the surface of the tongue
Stain with S-100
What non-keratinocyte cells are found in the oral epithelium?
Melanocytes
Langerhans cells
Merkel cells
Describe a melanocyte.
Stellate cells with clear cytoplasm found in basal layer of epithelium
Produce melanin
Describe a Langerhans cell.
Cells with clear cytoplasm and lobulated nuclei
Clearest in upper prickle cell layer
Dendritic function
Why does the base of the tongue have a nodular surface?
Lymphoid tisse
What epithelium covers the base of the tongue?
Non-keratinised, stratified squamous epithelium (oropharyngeal mucosa)
What are crypts?
Invaginations in surface of mucosa, lined by reticulated crypt epithelium (not stratified, loosely packed) to allow antigen passage
Packed with lymphoid tissue arranged as follicles
