1 - Epidermis and Derm Terms Flashcards
Describe the Epidermis? What is its function?
Derived from ectoderm, outermost layer of the skin, barrier function.
What are the layers of the epidermis from superficial to deep?
- Stratum corneum
- Stratum granulosum (granular layer)
- Stratum spinosum
- Stratum Basale
Describe the basay layer (stratum basale) of the epidermis?
Deepest layer, attached to the basement membrane, contains keratinocyte stem cells.
Also contains transient amplifying cells (TA) which are kind of like stem cells but divide a bunch and then become spinous cells.
Describe the stratum spinosum (spinous layer) of the epidermis?
Second deepest layer, composed of differentiating keratinocytes.
In most parts of the body it makes up most of the epidermis.
Synthesizes keratin.
*Spiney looking because of desmosome junctions*
What are the five types of junctions of the epidermis?
- Tight junctions: connection with actin
- Adherens junctions
- Desmosomes: contain keratins
- Focal adhesions
- Hemodesmosomes: one part of the desmosome
Describe the structure of keratin intermediate filaments?
They help connect cells
Describe the assembly of intermediate filaments?
Two rod domans of keratin form a heterodimer.
Two heterodimers form a tetramere.
Tetrameres lines up to form a protofilament, and several protofilaments becasue the intermediate filament.
What are the two types of granules in the stratum granulosum (granular layer)?
Keratohyalin granules and Lamellar granules (Odland bodies)
What are the keratohyalin granules in the stratum granulosum (granular layer)?
Filaggrin, involucrin, loricrin
What are the lamellar granules (odland bodies) in the stratum granulosum (granular layer)?
Tend to be made of fat.
Ceramides, cholesterol, fatty acids, hydrolytic enzymes
What are the characteristics of the stratum cornuem (cornified layer)? Where is it the thickest and thinnest?
Composed of corneocytes: lack nucleus and organelles (dead), held together by corneodesmosomes.
Primary barrier of the epidermis with variable thickness:
- No corneum in the ora, genital, and ocular mucosa
- Thinnest on the face and genetals
- Thickest on the palms and soles
What is keratinization?
The process of keratinocyte migration and maturation.
Average time is 28 days:
- stratum basale to stratum corneum > 14 days
- stratum corneum to shedding > 14 days
Describe the “bricks and mortar” concept of how keratinocytes turn into corneocytes?
The keratohyalin granules will form the cornified envelope (“bricks”) of the corneocyte for strength and shape.
The lamellar granules serve as the lipid envelope (mortar) around the corneocytes.
What is pemphigus vulgaris?
Acquired disease of the epidermis.
Autoimmune bullous disease involved auto-antibodies to desmosomal proteins (desmoglein 1 and 3). (desmosomes connect keratinocytes).
Results in intraepidermal blistering; just within the epidermis.
What are clinical features of pemphigus vulgaris?
- Flaccid, easily ruptured bullae
- Oral and mucosal lesions
- Nikolsky’s sign positive: rubbing on the skin by the blister causing it to shear off (pictured) due to loss of tight desmosomes holding it togehter
What is the treament for pemphigus vulgaris?
- Prednisone
- Azathioprine
- Mycophenolate mofetil
- Rituximab
What is Ichthyosis vulgaris? How common is it?
Autosomal dominant genetic condition
Mutations in profilaggrin gene that result in in a defective fillaggrin protein (this is what normally helps form the cornified later)
Affects 1 in 250