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What is the primary role of the oral mucosa in relation to microorganisms?
Which statement best describes the origin of the palatal and gingival epithelium?
Which of the following is NOT a function of the oral mucosa?
During which day of gestation does the primitive oral cavity begin to form?
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Which type of receptors in the oral mucosa are involved in reflex actions like swallowing?
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What component of saliva is essential for maintaining moist surfaces in the oral cavity?
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Which of the following types of epithelium is found in different regions of the oral cavity?
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Which cellular component provides a barrier against abrasions in the oral mucosa?
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What differentiates masticatory mucosa from lining mucosa?
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Which statement is true regarding Fordyce granules?
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Which type of mucosa is most abundant in the oral cavity?
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What is a major characteristic of non-keratinised mucosa?
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Which of the following structures is NOT an appendage found in mucosa?
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Which area of the oral cavity does the lining mucosa NOT cover?
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What is the primary role of minor salivary glands in the submucosa?
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What distinguishes the lining mucosa from masticatory mucosa?
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What component separates the epithelium from the underlying connective tissue in the oral mucosa?
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Which layer of the lamina propria is located between the rete ridges?
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Which cells are NOT typically found in the lamina propria?
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What is necessary for the metabolic needs of the avascular epithelium when the submucosa is absent?
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Which type of collagen is NOT found within the fibers of the lamina propria?
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Which structure is primarily associated with supporting the epithelium in the oral mucosa?
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Which type of mucosa is characterized as keratinised and masticatory?
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Which of the following components is NOT part of the ground substance in the lamina propria?
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Which type of mucosa is mostly absent of sensory function?
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What is the primary cellular composition of the transient inflammatory cells found in the oral mucosa?
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Among the following, which layer is directly above the lamina propria in oral mucosa?
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What component is especially prominent in the masticatory mucosa compared to lining mucosa?
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Which structure serves as an interface between the epithelium and the connective tissue in oral mucosa?
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What type of collagen primarily constitutes the lamina densa?
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What does the lamina lucida primarily consist of?
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What autoimmune condition could involve antibodies targeting the components of the mucosal desmosomes?
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Which component of the connective tissue is primarily responsible for the structural integrity of the lamina propria?
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Which statement accurately describes the rete ridges in the masticatory mucosa?
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What characterizes the vermilion zone of the lip?
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Which epithelium type has the fastest turnover rate?
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What changes occur in the oral mucosa with age?
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Which statement accurately reflects the condition of sebaceous glands in the elderly?
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What is the function of the intermediate zone in infants?
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How is the cell-mediated immunity affected with age?
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What describes the connective tissue changes observed in the elderly oral mucosa?
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What notable feature is seen in the dorsum of the tongue with age?
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Study Notes
Oral Mucosa
- Moist lining of the GI tract, nasal passages and other body cavities communicating with the external environment.
- Continuous with the skin (lips area) and with the rest of the gut (pharynx).
- Located between the skin and gastrointestinal (GI) tract.
- Shares similar components with skin and GI lining: a covering epithelium and underlying connective tissue.
Development of Oral Mucosa
- Primitive oral cavity (stomodeum) fuses to foregut after the rupture of the buccopharyngeal membrane (26 days of gestation).
- Structures that develop from branchial arches (tongue, epiglottis, pharynx) are covered by epithelium derived from endoderm.
- Palatal, buccal, gingival epithelium and epithelium covering the floor of the mouth and lips are ectodermal origin.
Functions of Oral Mucosa
-
Protection:
- Withstand compression, stretching, shearing, abrasion & bacterial influences.
- Barrier to microorganisms, toxins and various antigens.
- Immunological defense mechanisms: humoral and cell mediated.
-
Sensation:
- Temperature, pressure, pain, taste.
- Reflex receptors for swallowing, gagging.
-
Secretion:
- Maintenance of moist surface, buffering, secretion of antibodies.
- Major salivary glands produce saliva.
- Minor salivary glands are present in the submucosa except gingiva and anterior part of the hard palate.
-
Thermal regulation:
- In animals like dogs, panting helps regulate body temperature.
Differences Between Oral Mucosa and Skin
-
Oral mucosa:
- Absence of skin appendages but has salivary glands.
- Sometimes ectopic sebaceous glands (Fordyce’s granules).
- Smoother with less wrinkles.
- Deeply colored.
-
Skin:
- Hair follicles, sebaceous glands, sweat glands.
Fordyce Granules
- Common soft tissue variation seen in the oral cavity.
- Ectopic sebaceous glands.
- Characterized by yellowish-white papular lesions scattered throughout the oral mucous membrane.
- More common in the buccal mucosa.
Similarities Between Oral Mucosa and Skin
- Both have:
- Covering epithelium
- Underlying connective tissue
Organization of Oral Cavity
-
Outer vestibule:
- Bounded by lips & cheeks.
-
Oral cavity proper:
- Separated from vestibule by alveolus bearing teeth and gingiva.
- Superior: Hard and soft palate.
- Inferior: Floor of mouth & tongue base.
- Posterior: Fauces & tonsils.
Regional Variation of Oral Mucosa
-
Lining mucosa (60%):
- Mobile and distensible.
- Non-keratinized mucosa.
- Found in the whole mouth except gingiva, hard palate, and dorsum of the tongue.
-
Masticatory mucosa (25%):
- Attached to bone (muco-periosteum).
- Resists high levels of friction & compression.
- Keratinized type of mucosa.
- Found in gingiva, hard palate, and dorsum of the tongue.
-
Specialized mucosa (15%):
- Found in the dorsal surface of the tongue.
Lining Mucosa
- Composed of non-keratinized stratified squamous epithelium.
- Found in areas of the oral cavity where there is less wear and tear.
- Thinner and more flexible than masticatory mucosa.
Masticatory Mucosa
- Composed of keratinized stratified squamous epithelium.
- Found in areas of the oral cavity that are subject to more wear and tear, such as the hard palate and gingiva.
- Provides a protective barrier against abrasion and injury.
Composition of Oral Mucosa
-
Overlying epithelium:
- Epidermis in skin.
-
Basement membrane:
- Between epithelium & lamina propria.
-
Underlying connective tissue (lamina propria):
- Dermis in skin.
- Supports and nourishes the epithelium.
Epithelium-Connective Tissue Interface
- Epithelium projections into underlying connective tissue: rete ridges.
- Larger interface with stronger binding.
- Interface for metabolic exchange (epithelium has no blood vessels).
- More numerous, longer, and thinner in masticatory mucosa than lining mucosa.
Basement Membrane
- Composed of two zones:
- Lamina lucida: immediately underneath the epithelium.
- Lamina densa: finely granular or filamentous material of type IV collagen.
Clinical Considerations
- Auto-immune diseases: antibodies directed against any element of the desmosomes, hemidesmosomes, basement membrane.
- Split between epithelium & underlying connective tissue - sloughing of epithelium.
Lamina Propria
- Connective tissue supporting the epithelium.
- Two layers:
- Papillary LP between rete ridges.
- Reticular (net-like) LP.
- Cells: fibroblasts, macrophages, mast cells, inflammatory cells.
- Fibers: collagen (type I & III, IV & VII in basal lamina), elastic fibres.
- Ground substance.
Vascular Supply of Mucosa
- Deep plexus of vessels in submucosa or deep reticular layer.
- Secondary plexus in LP when submucosa is absent.
- Necessary for metabolic needs of the avascular epithelium.
Regional Variations in Mucosal Structure
-
Non-keratinized/ Lining/ Alveolar Mucosa:
- Labial mucosa inside lips.
- Cheek.
- Soft palate.
- Floor of mouth and ventral surface of the tongue.
-
Keratinized/ Masticatory Mucosa:
- Hard palate.
- Gingiva.
- Dorsum of the tongue.
Vermilion Zone
- Lacks appendages of skin.
- Sebaceous glands at the angles of the mouth.
- Lacks mucous glands, needs constant moistening with saliva.
- Keratinized translucent epithelium.
- Long and narrow connective tissue papillae with capillary loops.
- Junction between vermillion zone and labial mucosa is INTERMEDIATE ZONE - no granular layer, thick parakeratinised layer.
- Forms suckling pads in infants.
Turnover Times of Oral Epithelium
- Skin: 52-75 days.
- Gingiva: 41-57 days.
- Cheek: 25 days.
- Junctional epithelium: 5-6 days.
- Non-keratinized epithelium turns over faster than keratinized epithelium.
Age Changes of Oral Mucosa
- Mucosal surface is smoother, dryer, atrophic, and friable due to cumulative effect of systemic diseases and medication.
- Histologically: epithelium is thinner, smooth epithelium-connective tissue interface, flattening of epithelial ridges, lamina propria shows decreased cellularity and increased amount of cross-linked collagen.
- Dorsum of the tongue: glossy appearance, reduced number of filiform papillae, more prominent fungiform papillae.
- Declined cell-mediated immunity.
- Development of varicosities.
- Sebaceous glands of the lips and cheeks are more prominent, minor salivary glands show atrophic signs.
- Dryness of mouth, burning sensation, abnormal taste.
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Description
This quiz explores the structure, development, and essential functions of the oral mucosa, including its role as a barrier and its developmental origins. Delve into the protective mechanisms and the evolution of this critical lining in the gastrointestinal tract.
