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Oral Biology > Oral Mucosa > Flashcards

Oral Mucosa Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What’s a mucous membrane?

A
  • Moist lining of body cavities that communicate with the exterior
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2
Q

What’s Oral mucosa?

A
  • Mucous membrane lining of the oral cavity
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3
Q

What are the functions of the Oral Mucosa?

A
  1. Protection against compressive and shearing forces
  2. Barrier against microorganisms and toxins
  3. Humoral and cell mediated immunological defences
  4. Minor gland secretions provide lubrication, buffering and antibody secretions
  5. Sensations of touch, proprioception, pain and taste
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4
Q

What are the types of Oral Mucosa?

A
  1. Masticatory Oral Mucosa
    - Areas with high compression
    - Hard palate and gingiva
    - Keratinised epithelium
    - Thick Lamina Propria
  2. Lining Oral Mucosa
    - Subject to less compression and friction
    - Lips/cheeks/alveolar mucosa/soft palate/ ventral surface of the tongue/ Floor of the mouth
    - Mobile and distensible
    - Non-keratinised epithelium
    - Loose Lamina Propria
  3. Specialised Oral Mucosae
    - Dorsal surface of the tongue/ Lingual tonsils/ gingival attachment to teeth/ vermillion border
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5
Q

What are the components to Oral Mucosa?

A
  1. Epithelium
  2. Lamina Propria
  3. Submucosa
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6
Q

Oral Epithelium: What are the regions of Keratinised Epithelium?

A
  1. Stratum Germinativum (stratum basale)
  2. Stratum Spinosum (Prickle cell layer)
  3. Stratum Granulosum (Granular layer)
  4. Stratum Corneum (Keratinised or cornified layer)
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7
Q

Oral Epithelium: What are the regions of Non-Keratinised Epithelium?

A
  1. Stratum Germinativum (Stratum basale)
  2. Stratum Spinosum (Prickle cell layer)
  3. Stratum Intermedium (Intermediate layer)
  4. Stratum Superficiale
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8
Q

Stratum Germinativum: What are its key features?

A
  • Proginator cells of Keratinocytes
  • Single cell layer
  • Adjacent to the Lamina Propria and separated by a BASAL LAMINA
  • Cuboidal cells
  • Mitosis only occurs in this layer
  • Least differentiated cells within the oral epithelium
  • Stem cells are though to be within the epithelial ridges that project into the underlying lamina propria
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9
Q

What influence do maturing Stratium Germinativum cells have on the nearby cells?

A
  • Maturing cells produce growth inhibitors that restrict further cell division by negative feedback
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10
Q

Stratum Spinosum: What are it’s key features?

A
  • Round or Ovoid cells
  • Several layers thick
  • Show the 1st stages of maturation
  • Larger and rounder than the cells of Stratum Germinativum
  • Transition is characterised by the appearance of new Cytokeratin types
  • 1st appearance of Involcurin (precursor protein of the cornified envelope eventually found in the cornified layer)
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11
Q

How do the upper layers of the Stratum Spinosum differ?

A
  • Cells appear small and possess Odland bodies (intracellular membrane coating granules rich in phospholipids)
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12
Q

Where do the Odland bodies originate?

A
  • Golgi Apparatus
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13
Q

What’s a defining feature of Stratum Spinosum cells?

A
  • Desmosomes and Spines
  • Increased number of desmosomes
  • Slight shrinkage that occurs in most histological preparations causes the cells to separate at all points where desmosomes do not anchor together

= GIVES SPINY APPEARANCE

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14
Q

What does the term Parabasal layer refer to?

A
  • Refers to the deepest layer of cells of the Stratum Spinosum that lie next to the Stratum Germinativum
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15
Q

Stratum Granulosum: What are it’s key features?

A
  • Show further increase in maturation
  • Many organelles are reduced or lost (cytoplasm occupied by tonofilaments and tonofibrils)
  • Larger and flatter cells
  • Contain large number of Keratohyaline granules
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16
Q

What do Keratohyaline granules contain?

A
  • Precursor to filaggrin

= Profilaggrin

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17
Q

What’s special about the membrane coating granules?

A
  • They’re discharged into the extracellular space
  • Associated with the development of a barrier in the epithelium that limits the movement of substances between the cells
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18
Q

Stratum Corneum: What are its key features?

A
  • Final stage in maturation of keratinsied epithelium
  • Epithelial cells have lost all organelles (inc. nuclei & keratohyaline granules)
  • Cells filled with closely packed tonofilaments surrounded by the matrix protein filaggrin = COLLECTIVELY CALLED KERATIN
  • Can be termed Epithelial squames (these cells can shed)
  • The shedding is called DESQUAMTION and is facilitated by desmosomes weakening/disappearing
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19
Q

What feature does Stratum Corneum provide?

A
  • Mechanical protective function to the mucosa

- Varies in thickness (up to 20 cells)

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20
Q

What is Parakeratinised Epithelium?

A
  • Stratum Corneum cells with retained nuclei (albeit small + shrunken)
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21
Q

What is Ortho-keratin Epithelium?

A
  • Stratum Corneum cells without the nuclei
22
Q

What is Non-keratinised Epithelium?

A
  • 10% of cells in the oral epithelium are non-keratinocytes
  • Melanocytes/Langerhans cells/ Merkel cells
  • Lack tonofilaments and desmosomes
  • Will appear unstained when staining for Cytokeratins
23
Q

What are Cytokeratins?

A
  • A class of intermediate filaments specific to epithelial cells (cytoskeleton)
  • 20 Cytokeratin types (CK 1-20)

Products of 2 gene families which occur in pairs:

  • Neutral/basic type II = 1-8
  • Acidic type I = 9-20
24
Q

What are simple Cytokeratins?

A
  • Only expressed in simple epithelia

- CK 7, 8, 18

25
Q

What are Stratification Cytokeratins?

A
  • Pairs CK 5-14, 4-13, 1-10
26
Q

What are the functions of Cytokeratins?

A
  • Components of the cytoskeleton and cell contacts (desmosomes and hemidesmosomes)
  • Some are important in maintaining the metabolic integrity of the cell
  • CK14 related to innervation of the superficial mucosa through signal transduction
27
Q

What’s the basic distribution of Cytokeratins?

A
  • CK 5 & 14 are restricted to the basal and parabasal layers
  • CK 14 can be expressed in surpabasal layers
  • CK 1 & 10 OR 2 & 11 are expressed in the suprabasal layers of the masticatory mucosa (associated with terminal differentiation an keratinisation
  • Keratin layer is negative (no cytokeratins)
  • CK 4 & 13 are present in the supreabasal layer in the lining mucosa
28
Q

What are CK 16 and 6 associated with?

A
  • Rapid turnover epithelia
29
Q

What is CK 19 associated with?

A
  • Marker for basal keratinocytes in lining mucosa
30
Q

What Cytokeratins does the ventral surface of the tongue express?

A
  • CK 5, 6, 14
31
Q

What Cytokeratins does the soft palate lining express?

A
  • CK 7, 8, 18, 19
32
Q

What are the clinical considerations related to Cytokeratin expression?

A
  • Their expression can be alter in states of inflammation
  • Can be used in diagnostic histopathology
  • Dysplastic changes revealed by CK alterations
33
Q

Non-keratinocytes within Epithelium: What are Melanocytes and what are their functions?

A
  • Melanin producing cells (responsible for skin pigmentation)
  • Located in Stratum Germinativum
  • Derived from Neural Crest cells - present in skin after 8 weeks intrauterine life
  • Melanin is produced using tyrosinase
  • Difference in the degree of pigmentation is a result of a combination of size of the cells and the degree of branching - NOT THE ABSOLUTE NUMBER
34
Q

What is the pigment contained in?

A
  • Small granules called MELANOSOMES
35
Q

How do Keratinocytes take up melanin?

A
  • Each Melanocyte can contact up to 40 keratinocytes
  • Keratinocytes release mediators important for melanocyte function
  • Keratinocytes take up melanin by actively phagocytosing the melanocytes dendritic tips
36
Q

What’s Peutz Jeghers Syndrome?

A
  • Mucoctaneous pigmentation (resembling freckling, appears in infancy)
  • Buccal mucosa and lips are mainly affected
  • Autosomal dominant
37
Q

What’s Hyperkeratosis associated with?

A
  • Melanic pigmentation
  • Smoking can cause melanocyte activation/reaction to the constant irritation
  • Melanin incontience: melanin present in the subepithelial macrophages having leaked out of melanocytes and basal cells
38
Q

What are Langerhans cells and what’s their function?

A
  • Dendritic, Antigen Presenting Cells (APC’S)
  • Located above the basal layer
  • Derivative of bone marrow precursors - leaving blood stream and enter Lamina Propria before penetrating Stratum Germinativum
  • Important role in contact hypersensitivity reaction of the skin
  • Role in anti-tumour immunity
  • Role in graft rejection
39
Q

What are Merkel cells and what’s their function?

A
  • Found in Stratum Germinativum
  • Closely apposed to nerve fibres
  • Contain CK8/18 & 20
40
Q

What’s the Lamina Propria?

A
  • Connect tissue underlying the oral epithelium
41
Q

How many layers does the Lamina Propria have?

A

x2

  • Superficial papillary layer (loose thin collagen fibres)
  • Deep reticular layer (thick parallel collagen bundles)
42
Q

Are fibroblasts present in the lamina propria?

A
  • Yes
  • Typical of those found in loose CT
  • Constantly producing and secreting extracellular fibres and ground substance
43
Q

What the composition of Lamina Propria’s Extracellular matrix?

A
  • Collagen (90% type I, 8% type III)
  • Non-fibrillar collagen
  • Elastin
  • Oxytalan
  • Proteglycans & Glycoproteins hydrated gel consistency
44
Q

What are the other cells present in the Lamina Propria?

A

Macrophages:

  • Seen in their fixed, inactive state (known as Histocytes)
  • Difficult to distinguish from Fibroblasts (have a smaller+darker nuclei)
  • Also Antigen Presenting Cells (APC’S)

Mast Cells

  • Mononuclear, spherical/elliptical in shape
  • Contain histamine+heparin intracellular granules
  • Role in vascular homeostasis
  • Type I hypersensitivity
45
Q

What’s the Epithelial CT Interface?

A
  • A thin layer called the basal lamina (basement membrane

- Consists of fibril and ground substance complex

46
Q

What are the Basal Lamina’s two zones?

A
  1. Lamina Lucida (20-40nm thick), immediately
    under the epithelium
  2. Lamina Densa (Deep to the Lamina Lucida)
47
Q

What’s the origin of the basal lamina components?

A
  • Synthesised by the Epithelial cells
48
Q

What’s the Lamina Lucida made of?

A
  • Predominantly Laminin (glycoprotein)

- Cements Collagen type IV between Lamina Densa and the Epithelial cells

49
Q

What’s the Lamina Densa made of?

A
  • Type IV Collagen coated with heparan sulphate
  • Thick collagen fibres attach to the lamina densa to link the basal lamina to the CT
  • Fibronectin is found and may bind fibroblasts and proteoglycans to the LD
50
Q

What’s the role of Basal Lamina?

A
  • Provides mechanical adhesion between the epithelium and the CT
  • Molecular barrier
  • Role in response to tissue injury

Oral Biology (33 decks)

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