Skin Flashcards
What are the 2 main layers of the skin?
Epidermis and dermis
Describe the structure of the epidermis? (epithelium type, cell type, layers etc.)
Stratified squamous epithelium Major cell type = keratinocytes 4 main layers: 1. stratum basale 2. stratum spinosum 3. stratum granulosum 4. stratum corneum
What are keratins? Where are they found?
Produced by keratinocytes
intermediate filament
most abundant protein in the stratum corneum, hair and nails
exists as acidic and basic pairs (e.g. K5/K14)
What is the basement membrane composed of?
Laminin 332
Collagen IV
Collagen VII
Describe the structure of the stratum spinosum.
3-4 cell layers thick
numerous desmosomes give cells a spiny appearance
detachment from basement membrane triggers terminal differentiation –> stop proliferating + secrete proteins that will help form the impermeable layer
Describe the structure of the stratum granulosum.
2-3 cell layers thick
characterised by large granules of keratohyalin
- filaggrin, involucrin, loricrin are insoluble proteins that will eventually become part of the external barrier
Describe the structure of the stratum corneum.
main part of protective barrier - dense and insoluble
thick cornified envelope
cross-linked by transglutaminase
cells in cornified layer are dead
intercellular lipids (ceramides) maintain moisture
What is an adherens junction, what is its role?
cadherin receptor linked to actin cytoskeleton
provides mechanical strength + integrity
What is a desmosome, what is its role?
cadherin receptor linked to keratin cytoskeleton
provides mechanical strength + integrity
What is a tight junction, what is its role?
Claudin and occludin sealing an intercellular space
prevents the movement of molecules between the cells
What is a gap junction, what is its role?
Intercellular pore made up of connexins
allow nutrients to reach from the basal layer up to the epidermis
Name the 3 layers of the dermis.
Papillary
Reticular
Adipose
What is the most abundant cell type in the dermis and what does it synthesise?
Fibroblast
Synthesises: collagen, elastin and proteoglycans (all make up ECM)
Describe the structure of the papillary layer.
Directly beneath epidermis and BM
contains many capillaries
fine, randomly oriented collagen (type III collagen)
elastic and flexible
Describe the structure of the reticular layer.
Large, more aligned and densely packed with collagen fibres
Provides mechanical strength
What are the two different types of hair follicles?
Vellus: body hair (fine + non pigmented)
Terminal: scalp and secondary sexual hair
Which cells control hair growth?
Dermal papilla fibroblasts
Where are hair follicle stem cells located and what do they express?
Located in the bulge region
express keratin 15
What are the hair follicle stem cells responsible for in normal and wounded conditions?
Normal: produce hair follicle structures
Wounded: sebaceous glands and epidermis
What are the 3 different phases of the hair cycle and how long does 1 hair cycle take?
Phases:
- Anagen: active
- Catagen: regressive
- Telogen: resting (then reenters anagen)
1 hair cycle lasts ~3 months
What is the eccrine sweat gland responsible for and what are the 2 main components?
Thermoregulation
components:
1. excretory ducts
2. secretory coil
What is an apocrine gland?
sweat gland associated with hair (axilla + pubic region)
secretions are odourless –> broken down by bacteria and this releases volatile fatty acids
What is a melanocyte? Where is it found? What does it produce?
dendritic cell that protects against UV
found in epidermis on BM and hair matrix
produces melanin on melanosomes; 2 types:
1. eumelanin - brown
2. pheomelanin - red
What is a Langherhan cell and where is it found?
dendritic cell and an antigen presenting cell (1st line of defence)
found in basal and spinous layers
Where are Merkel cells found and what are they responsible for?
found in stratum basale
responsible for sensory perception (light touch + pressure)
have properties of epidermal cells
Where are Mast cells found and what are they responsible for?
found in the dermis
stimulate an immune response - secrete histamine
What is the difference between a superficial, partial thickness and full thickness wound?
Superficial: epidermis
Partial thickness: epidermis + dermis
Full thickness: epidermis, dermis + hypodermis
What are the 3 main stages of normal wound healing?
- Inflammation (minutes -> days): recruitment of neutrophils and macrophages; phagocytes also come in
- Proliferation (days): keratinocytes and fibroblasts will increase proliferation for regeneration and repair
- Maturation (weeks -> months): remodelling and restructuring tissue
What are the main complications with wound healing?
Infection
Chronic (not healed after 6 weeks)
Scarring
