Skin Structure & Function Flashcards
1
Q
What is the Epidermis, and what are its properties?
A
- Outermost layer of skin
- Avascular - lack of blood vessels
- Acts as a protective barrier
- Contains 4 main types of cells; Keratinocytes, Melanocytes, Langerhans and Merkel
- Has 5 layers; Stratum corneum, Stratum lucidum, Stratum Granulosum, Stratum spinosum, Stratum basal.
2
Q
What are Melanocytes, and what are their properties?
A
- Cells which produce Melanin, a protective skin darkening pigment
- Protects against UV radiation
- Located in the Stratum basal layer 4. Stimulates keratinocyte production, thickening the epidermis
3
Q
What are Langerhans, and what are their properties?
A
- Dendritic cells located in the stratum spinosum
- Alerts immune system of harmful substances
- Highly specialised macrophages, take part in destruction of pathogens
- Part of hypersensitivity and allergic reactions
4
Q
What are the five layers of the epidermis?
A
- Stratum Corneum
- Stratum Lucidum
- Stratum Granulosum
- Stratum Spinosum
- Stratum Basal
5
Q
What are Keratinocytes, and what are their properties?
A
- Cells which produce keratin
- Forms a protective barrier resistant to physical and chemical damage
- Held together by desmosomes
6
Q
What are properties of the Stratum basal layer?
A
- Comprised mostly of keratinocytes
- Also include melanocytes and merkel cells
- Stem cells mitose to produce keratinocytes here, replacing corneocytes which have shed (in the stratum corneum layer)
- The cells are attached to the dermo-epidermal junction by hemi desmosomes
7
Q
What are properties of the Stratum Spinosum layer?
A
- Cells from the basal layer migrate upwards to this layer and change shape to polygonal.
- Develop keratin filaments (tonofilaments)
- Some tonofilaments project out of the cell desmosomes
- These filaments fill with others and form intercelluar bridges to add resilience.
8
Q
What are Desmosomes?
A
- Bridges between cells
- Provide robust barrier against trauma, particularly shearing forces
3 Loss of adhesion could result in blistering diseases,
9
Q
What are properties of the Stratum Granulosum?
A
- Cells migrate up to this level and begin to flatten out from their polygonal shapes
- Cells begin to lose nuclei and organelles, undergoing programmed cell death
- Granules of keratohyalin organise keratin into thick bundles, increasing strength
10
Q
What is filaggrin and why is it important?
A
- it is a filament associated protein which binds to keratinocytes
- They are important as they retain the water within keratinocytes
11
Q
What are properties of the Stratum Lucidum?
A
- visible on soles, palmes, fingertips and anywhere with thick skin.
- thin layer of dead keratinocytes.
12
Q
What are properties of the Stratum Corneum?
A
- Uppermost layer, filled with Keratin and filaggrin
- Cells change shape to hexagonal, and become cornified.
13
Q
What is Desquamation?
A
- Essentially the shedding of the skin
- Includes breaking the desomosome links between corneocytes
- Can only function well in the presence of a well-hydrated Stratum corneum
- Desquamation is abnormal in the absence of hydration, leading to thick and dry skin.
14
Q
What are properties of the dermis?
A
- Cells - composed of mainly fibroplasts, but also contains lymphocytes, langerhans, macrophages and mast cells
- Fibres - 70% collagen, the protein which gives toughness and strength. Also contains Elastin, which makes the skin pliable
15
Q
What are the layers of the Dermis?
A
- Papillary
- Reticular