Epidermis and Dermis Flashcards
What are the skin’s major regions?
- Epidermis
- Dermis
- Hypodermis
What is the epidermis?
A keratinized stratified squamous epithelium made up of 4 cell types and consists of 4 or 5 layers
What is the dermis?
Tough, leathery layer composed of fiberous connective tissue
What two tissues make up the epidermis?
Keratinized stratified squamous and nervous tissue
What are the 4 cells in the epidermis?
- Keratinocytes
- Melanocytes
- Langerhans’ cells
- Merkel cells
Keratinocytes
- Produce keratin
- Most epidermal cells are keratinocytes
Melanocytes
- Cells that create melanin
- Provides color to skin, hair, and eyes
- helps protect skin from UV rays
Langerhans’ Cells
- Epidermal macrophages that help activate the immune system
Merkel (nervous) Cells
- Present at epidermal-dermal junction
- Shaped like a spiky sphere, functions as a sensory receptor for touch
What are the 5 epidermal layers? (Deep-Superficial)
- Stratum basal
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Stratum Basal
- Deepest to epidermal layer firmly attached to the dermis.
- Consists of a single row of the youngest keratinocytes (cells undergo rapid division)
- Most vascularized layer
Stratum Spinosum
- Several cell layers (3-5) thick that consists of a weblike system of intermediate filaments.
- Span cytosol to attach to desmosomes
- Consists of prekeratin filaments
- Among keratinocytes are melanin granules and Langerhans’ cells
Stratum Granulosum
- 3-5 cell layers
- Keratinocyte appearance changes drastically
- Keratohyalin (keratin in upper layers) & lamellated granules (water proofing/glycolipid)
- Tight junctions for waterproof layer
- Cells flatten cause keratin replaces cytoplasm and organelles
Stratum Lucidum
- Only visible in thick skin
- Few layers of clear, flat, dead keratinocytes with indistinct boundaries
Stratum Corneum
Consists of 20-30 cell layers thick, it is protected by keratin and the thickened plasma membrane of cells
“Epi”
above
“derm”
skin
“hypo”
Below
Thick vs. Thin
Thick:
* has lucidum (sole of foot and palms of hands)
Thin:
*No lucidum (everywhere else)
List the steps for cell keratinization
- Rapid cell division (basal layer)
- Older layers get pushed up (as they are pushed up, they die)
- Cytoplasm is replaced by keratin
Some Tissue in Dermis (list 3-4)
- Adipose
- Fibrous connective tissue
- Blood
- Nervous
Cells within Dermis
- Fibroblasts
- Macrophages
- Mast cells
- White blood cells
What are the layers in the dermis?
- Papillary
- Reticular
Papillary
- Areolar connective tissue with collagen and elastic fibers.
- Epidermal ridge/ dermal papillae create fingerprint
Reticular
- Dense irregular tissue
- 80% of the thickness of dermis
Name the 4 different skin colors
- Melanin
- Carotene
- Hemoglobin
4.Cyanosis
Melanin
Provides protection from UV rays
Carotene
- Yellow-orange
- Pigment found in plants such as carrots
- Mostly seen in palms & soles where corneum is thickest
Hemoglobin
- Pinkish hue of fair skin
- High O2 circulation through dermal capillaries causing the epidermis to be nearly transparent
Cyanosis
- Blue
- Low O2 circulation
What are the 5 emotional/disease impacts on skin color?
- Redness/Erythema
- Pallor/Blanching
- Jaundice
- Bronzing
- Bruises
Redness/Erythema
- Reddened skin
- Embarrassment
Pallor/Blanching
- Paleness
- Low blood pressure, fear, anemia, etc.
Jaundice
- Yellow cast
- Liver disorder
Bronzing
- Bronze or metallic
- Addison’s disease, hypofunction of adrenal cortex
Bruises
- Reveals where blood escaped from circulation and clotted beneath the skin
Which epidermal cell is a macrophage, arises from bone marrow and serves an immune function?
Langerhans’ cells
Cells of the stratum spinosum have many interlocking desmosomes that will remain between the cells as they migrate to the stratum corneum. These cell junctions serve the body by …
Preventing mechanical stress or trauma from damaging the epidermis
A needle would pass through the epidermal layers of the forearm in which order?
Corneum, granulosum, spinosum, and Basale
What types of fibers make up the matrix?
Collagen, elastic, and reticular
Dermicidin
- Acid mantle
- Kills bacteria on the skin
Why does the epidermis and the dermis undulate?
to significantly increase the surface area of contact between the two layers, allowing for better exchange of nutrients, fluids, and signals between them
In terms of both function and benefit, why are surface keratinocytes dead?
The stratum corneum is so far removed from the underlying blood supply in the dermis that diffusion of nutrients is insufficient to keep the ells alive.
Why does sunburned skin peel in sheets?
When skin peels as a result of sunburn damage, the deeper layers of the stratum corneum, which still maintain their desmosome connections, detach. The desmosomes hold the cells together within the layers.
