Topic 3

Question 1

What are the essential functions of the skin?

Answer 1

• retention of moisture
• barrier against harmful substances
• protection from microbes
• sensory activity
• production of vitamins
• regulation of body temperature

Question 2

What is the epidermis?

Answer 2

outer layer of the skin and acts as the body’s major barrier against external stresses.

Question 3

What are the layers of the skin, bottom to top?

Answer 3

• Dermis, Stratum basale, Stratum Spinosum, Stratum Granulosum, Stratum Lucidum, Stratum Corneum

Question 4

What are keratinocytes?

Answer 4

main cell type of epidermis

Question 5

What does the stratum basale consist of?

Answer 5

Cuboidal-shaped keratinocytes

Question 6

What does the stratum spinosum consist of?

Answer 6

Interconnected cells to form a stable network

Question 7

What does the Stratum Granulosum consist of?

Answer 7

Characterised by cells with the granular cytoplasm

Question 8

What does the stratum lucidum consist of?

Answer 8

a layer of dead, flat transparent cells. Only found in palms and soles

Question 9

What does the Stratum Corneum consist of?

Answer 9

layers of hexagonal shaped, non-viable cells called corneocytes. A highly insoluble kertatin shell provides the natural water-retaining barrier of the skin.

Question 10

What are melanocytes?

Answer 10

dendritic cells that produce melanosomes. Lelanosomes are pigment-producing granules that are transferred to keratinoctyes. Melanin granules form a protective cap over the nucleus of the keratinocyte protecting it from photo damages.

Question 11

What are merkel cells?

Answer 11

closely associated with cutaneous nerves and seem to be involved in touch sensation

Question 12

What are langerhans cells?

Answer 12

serve an immunologic role in the skin. These antigen presenting cells take up foreign invaders and process them.

Question 13

What is the dermis composed of?

Answer 13

1 - the papillary
2 - reticular dermis

Question 14

What are the cellular components of the dermis?

Answer 14

fibroblasts - produce collagen - which has great tensile strength and forms the major consistuent of the dermis
elastin - makes up only a small proportion of the bulk

Question 15

What is embedded in the fibrous tissue of the dermis?

Answer 15

• dermal vasculature
• lymph vessels
• nerve cells and fibres
• sweat glands
• hair roots
• striated muscles

Question 16

What are acute wounds?

Answer 16

due to mechanical stress, exposure to corrosive chemicals, heat, light and electrical shock.
period of 8-12 weeks

Question 17

What are chronic wounds?

Answer 17

due to diseases, inflammation and infections. They require a healing time that exceeds 12 weeks and often persist in a pathologival condition of inflammation.

Question 18

What are the 4 stages of wound healing?

Answer 18

1 - Homeostasis
2 - Inflammation
3 - Proliferation
4 - Remodeling

Question 19

What occurs during Homeostasis?

Answer 19

immediate response of the body to the injury.
Injured blood vessels are constricted
a fibrin clot is produced to stop bleeding
fibrin clot provides scaffold for inflammatory cells and initiates the subsequent inflammatory mechanism

Question 20

What occurs during Inflammation?

Answer 20

Begins with the release of cytokines and arrival of neutrophils to the wound site.
Neutophils removes foreign particles, dead cells and bacteria
Monocytes aare recruited and transform to activated macrophages to mediate inflammation, immune reponse, cell proliferation and tissue regeneration.

Question 21

What occurs during proliferation?

Answer 21

Cells at the wound edge release cytokines and growth factors to stimulate proliferation and migration of endothelial cells
(angiogenesis - formation of new blood vessels)
fibroblasts proliferate and invade the fibrin clot to form contactile granulation tissue
they mature into myofibroblasts and contract the wound to enable closure, they produce and deposit ECM proteins to form a scar.

Question 22

What occurs ar remodelling?

Answer 22

an acellular scar tissue is formed with the maturation of ECM proteins and increased organisation of collagen fibrils
disorganised collagen becomes lamellar and a mature scar tissue is formed.

Question 23

What is the integer?

Answer 23

it is a bioactive layer
top layer - meshed silicon membrane
is the middle - collagen glycosaminoglycan
pore volume fraction 98%
average pore diameter of 30-120um

Question 24

What is the meshed silicon membrane?

Answer 24

• control water vapour loss
• provides a flexible adherent covering
• designed to be used in conjunction with negative pressure wound therapy

Question 25

What is collagen glycosaminoglycan biodegradable matrix?

Answer 25

- provides a scaffold for cellular invasion and capillary region - scaffold is eventually remodeled as the patients cells rebuild the damaged site

Question 26

What is apligraf?

Answer 26

allogeneic epidermal keratinocytes and fibroblasts suspended in a bovine collagen matrix and organized into a skin-like structure.

Question 27

Advantages of engineered skin

Answer 27

- no requirement of donor skin grafts - reduced short and long term complications - rapid regeneration of the injured skin

Question 28

Limitations of engineered skin

Answer 28

- time consuming process. cells usually require two or three weeks of cell culture before they are ready for grafting - no differentiated structure such as sweat and sebaceous glands and hair follicle are formed because only two cell types, fibroblasts and keratinocytes are used - high cost

Question 29

What is an ideal wound dressing?

Answer 29

- provide or maintain moist environment to enable cell migration across the wound surface - remove excess of wound exudate to relieve tissue macreation and reduce pain and swelling - allow gas exchange, particulary oxygen which is required for the different phases of wound healing - provide thermal insulation to main constant temperature - provide protection against bacteria to reduce the risk of infections

Question 30

What are passive dressings?

Answer 30

include gauze, plasters or natural/synthetic fibres. They are dry and used as promiary or secondary dressings for protecting the wound against contaminations.

Question 31

What are interactive dressings?

Answer 31

available in the forms of films, foam etc, used as a barrier against penetration of bacteria to the wound environment

Question 32

Interactive - what are semi permeable films?

Answer 32

- made of transparent and adherent polyurethane films which permits tranmission of water vapour, o2 and co2 from the wound - inspection of wound closure is also possible without removal of wound dressing because of transparent films

Question 33

Interactive - what are semi permeable foams?

Answer 33

- composed of hydrophobic and hydrophilic foams. - hydrophobic layer is the outer surface, protection from liquid but allow gaseous exchange and water vapour - hydrophilic layer absorbs and retains exudates - absorb varying quantities of wound drainage depending upon the wound thickness

Question 34

Interactive - hydrogels?

Answer 34

- dressings insoluble hydrophilic materials made from synthetic polymers - high water content (70-90%) - temperature of cutaneous wounds is decreased by hydrogels providing soothing anf cooling effect - recommended for dry chronic wounds, necrotic wounds, pressure ulcers and burn wound

Question 35

Interactive - hydrocolloids?

Answer 35

- consist of 2 layers, inner colloidal layers and outer water - impermeable layer - they form gels when in contact with the wound exudate and provide a moist environment. - recommended for lightly to moderately exuding wounds, minor burn wounds

Question 36

What are are bioactive dressings?

Answer 36

produced from natural material such as collagen, hyaluronic acid, chitosan, alginate and elastin -those dressings sometimes incorporated growth factors and antimicrobial agents to promote the wound healing process

Question 37

How is collagen important in healing?

Answer 37

collagen is the principle structural component of ECM and most abundant protein collagen fibres facilitate cell migration to the wound site

Question 38

How does hyaluronic acid help during healing?

Answer 38

involved in different phases; activation of inflammatory response, keratinocyte migration and proliferation and scar formation