Chapter 1- Epidermis Flashcards
Name the four distinct cell types within the epidermis
- Keratinocytes 2. Melanocytes 3. Langerhans cells 4. Merkel cells
Keratinocytes compose what percentage of epidermal cells?
85%
Melanocytes compose what percentage of epidermal cells?
5%
Langerhans cells compose what percentage of epidermal cells?
3 to 8%
Merkel cells compose what percentage of epithelial cells?
2%
The epidermis is divided into 5 layers. Name them from inner to outer
- basal layer (Stratum basale) 2. spinous layer (stratum spinosum) 3. granular layer (stratum granulosum) 4. clear layer (stratum lucidum) 5. horny layer (stratum corneum)
The epidermis of cats and dogs in haired skin is how many nucleated cell layers (not counting the horny layer)?
2 to 3
The haired epidermis of cats and dogs is how thick? (range)
0.1 to 0.5 mm
Where is the thickest epidermis found and how thick does it measure there?
footpads and nasal planum- 1.5 mm
The footpad epidermis is smooth in dogs or cats? Papillated and irregular in dogs or cats?
Cats- smooth; Dogs- papillated and irregular
Projections of the epidermis into the underlying dermis are called____ ______.
rete ridges
What are rete ridges?
projections of the epidermis into the underlying dermis
Where are rete ridges NOT found?
they are NOT found in the normal hair bearing skin of cats and dogs
Where are rete ridges found?
foot pad, nasal planum epidermis, scrotum
Name the cell types that compose the stratum basale
single row of columnar to cuboidal cells
Where do the columnar and cuboidal cells of the stratum basale rest upon? (what structure)
basement membrane
Basement membrane separates what two layers?
dermis from the epidermis
The columnar and cuboidal cells of the stratum basale are mostly what distinct cell type?
keratinocytes
The keratinocytes in the basal layer are constantly reproducing and pushing in which direction to replenish epidermal cells?
upward
There is morphologic and functional heterogenicity in what kind of keratinocytes (a layer)
basal keratinocytes
Describe the different functions of the different populations of basal keratinocytes
- anchor the epidermis 2. serve as a proliferative and reparative (stem cell) function
Keratinocyte differentiation is AKA
keratinization
Define keratinization
A genetically programmed complex series of metabolic events and morphologic changes
Cells of the stratum basale contain which keratin filaments?
K5 and K14
K5 and K14 keratin filaments attach to neighboring cells through _______ and to the basement membrane zone at _______
desmosomes; hemidesmosomes
The major cell adhesion junction of epithelial tissues is called ______.
desmosomes
Desmosomes provide the anchor for intermediate filaments connecting ___ to ______; They also anchor ________cells together
nuclear envelope to the cell membrane; adjacent cells together
This major cell adhesion junction stabilizes the structure of the _____.
epidermis
The molecular components of the desmosome belong to what 3 major gene families?
- plakins 2. armadillo proteins 3. desmosomal cadherins
Plakins, armadillo proteins, and desmosomal cadherins are a common target for what?
many diseases
What are hemidesmosomes?
Junctional complexes distributed along the inner aspect of basal keratinocytes
What is the major role of hemidesmosomes?
epidermal-dermal adhesion
Various inherited defects in the hemidesmosome-anchoring filament components are known to produce what 3 diseases?
- epidermolysis bullosa 2. pemphigoid 3. bullous systemic lupus erythematosus
What are integrins?
A large family of cell surface adhesive receptors
Integrins are important in what type of interactions?
cell-cell and cell-matrix interactions
Can integrins also act as signal transducers?
Yes
Each integrin consists of a heterodimer of which two subunits?
alpha and beta
Are the alpha and beta subunits of integrins covalently or noncovalently associated?
noncovalently
In the epidermis, integrin expression is normally confined to which layer?
basal
Which integrin subunits are most abundant in the epidermis?
alpha 2, alpha 3, beta 1, alpha 6, beta 4
Structural Target: Intermediate Filaments
Molecular Target: K5/K14
Congenital Disease:
Acquired Disease:
Congenital Disease: Epidermolysis bullosa simplex
Acquired Disease: Ocular cicatricial pemphigoid
Structural Target: Desmosomes
Molecular Target: Desmoglein 1, desmoglein 3
Acquired DIsease:
Pemphigus vulgaris, pemphigus foliaceous
Structural Target: Desmosomes
Molecular Target: Plakoglobin, desmoplakins
Congenital Disease:
Acquired Disease:
Congenital Disease: Ectodermal dysplasia, skin fragility
Acquired Disease: Paraneoplastic pemphigus
Structural Target: Hemidesmosome transmembrane molecules
Molecular Target: alpha6Beta4 Integrin
Congenital Disease:
Acquired Disease:
Congenital Disease: Junctional epidermolysis bullosa
Acquired Disease: Bullous pemphigoid, mucous membrane pemphigoid
Structural Target: Hemidesmosome
Molecular Target: BPAG1e (BP230), collagen XVII (BP180, BAPG2, LAD01)
Congenital Disease:
Acquired Disease:
Congenital Disease: Epidermolysis bullosa (humans, collagen XVII)
Acquired: Bullous pemphigoid, mucousmembrane pemphigoid, linear IgA bullous disease
Structural Target: Lamina densa (BMZ)
Molecular Target: Laminin
Congenital Disease:
Acquired Disease:
Congenital Disease: Junctional epidermolysis bullosa
Acquired Disease: Mucous membrane pemphigoid, acquired junctional epidermolysis bullosa
Structural Target: Anchoring fibrils (BMZ)
Molecular Target: Type VII collagen
Congenital Disease:
Acquired Disease:
Congenital Disease: Dystrophic epidermolysis bullosa
Acquired Disease: Epidermolysis bullosa acquisita, type 1 bullous systemic lupus erythematosus
