Skin

Question 1

What are the 2 main layers of the skin?

Answer 1

Epidermis and dermis

Question 2

Describe the structure of the epidermis? (epithelium type, cell type, layers etc.)

Answer 2

Stratified squamous epithelium 
Major cell type = keratinocytes
4 main layers:
1. stratum basale 
2. stratum spinosum
3. stratum granulosum 
4. stratum corneum

Question 3

What are keratins? Where are they found?

Answer 3

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)

Question 4

What is the basement membrane composed of?

Answer 4

Laminin 332
Collagen IV
Collagen VII

Question 5

Describe the structure of the stratum spinosum.

Answer 5

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

Question 6

Describe the structure of the stratum granulosum.

Answer 6

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

Question 7

Describe the structure of the stratum corneum.

Answer 7

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

Question 8

What is an adherens junction, what is its role?

Answer 8

cadherin receptor linked to actin cytoskeleton

provides mechanical strength + integrity

Question 9

What is a desmosome, what is its role?

Answer 9

cadherin receptor linked to keratin cytoskeleton

provides mechanical strength + integrity

Question 10

What is a tight junction, what is its role?

Answer 10

Claudin and occludin sealing an intercellular space

prevents the movement of molecules between the cells

Question 11

What is a gap junction, what is its role?

Answer 11

Intercellular pore made up of connexins

allow nutrients to reach from the basal layer up to the epidermis

Question 12

Name the 3 layers of the dermis.

Answer 12

Papillary
Reticular
Adipose

Question 13

What is the most abundant cell type in the dermis and what does it synthesise?

Answer 13

Fibroblast

Synthesises: collagen, elastin and proteoglycans (all make up ECM)

Question 14

Describe the structure of the papillary layer.

Answer 14

Directly beneath epidermis and BM
contains many capillaries
fine, randomly oriented collagen (type III collagen)
elastic and flexible

Question 15

Describe the structure of the reticular layer.

Answer 15

Large, more aligned and densely packed with collagen fibres

Provides mechanical strength

Question 16

What are the two different types of hair follicles?

Answer 16

Vellus: body hair (fine + non pigmented)
Terminal: scalp and secondary sexual hair

Question 17

Which cells control hair growth?

Answer 17

Dermal papilla fibroblasts

Question 18

Where are hair follicle stem cells located and what do they express?

Answer 18

Located in the bulge region

express keratin 15

Question 19

What are the hair follicle stem cells responsible for in normal and wounded conditions?

Answer 19

Normal: produce hair follicle structures
Wounded: sebaceous glands and epidermis

Question 20

What are the 3 different phases of the hair cycle and how long does 1 hair cycle take?

Answer 20

Phases:

1. Anagen: active
2. Catagen: regressive
3. Telogen: resting (then reenters anagen)

1 hair cycle lasts ~3 months

Question 21

What is the eccrine sweat gland responsible for and what are the 2 main components?

Answer 21

Thermoregulation
components:
1. excretory ducts
2. secretory coil

Question 22

What is an apocrine gland?

Answer 22

sweat gland associated with hair (axilla + pubic region)

secretions are odourless –> broken down by bacteria and this releases volatile fatty acids

Question 23

What is a melanocyte? Where is it found? What does it produce?

Answer 23

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

Question 24

What is a Langherhan cell and where is it found?

Answer 24

dendritic cell and an antigen presenting cell (1st line of defence)
found in basal and spinous layers

Question 25

Where are Merkel cells found and what are they responsible for?

Answer 25

found in stratum basale
responsible for sensory perception (light touch + pressure)
have properties of epidermal cells

Question 26

Where are Mast cells found and what are they responsible for?

Answer 26

found in the dermis

stimulate an immune response - secrete histamine

Question 27

What is the difference between a superficial, partial thickness and full thickness wound?

Answer 27

Superficial: epidermis
Partial thickness: epidermis + dermis
Full thickness: epidermis, dermis + hypodermis

Question 28

What are the 3 main stages of normal wound healing?

Answer 28

1. Inflammation (minutes -> days): recruitment of neutrophils and macrophages; phagocytes also come in
2. Proliferation (days): keratinocytes and fibroblasts will increase proliferation for regeneration and repair
3. Maturation (weeks -> months): remodelling and restructuring tissue

Question 29

What are the main complications with wound healing?

Answer 29

Infection
Chronic (not healed after 6 weeks)
Scarring