Structure And Function Of Skin

Question 1

What are stem cells?

Answer 1

Undifferentiated cells, can self-renew plus create new cells that will differentiate into specific cell types

Question 2

What are fibroblasts?

Answer 2

Connective tissue cells that synthesis collagen through self renewal

Question 3

What are the three main layers of the skin and what are their overall functions?

Answer 3

Epidermis
- permeability barrier
- UV protection
- vit D synthesis
Epidermis and dermis
- wound repair 
- pathogen barrier
Epi, dermis and hypodermis
- thermoregulation, sensation and physical appearance
Other facts:
-Extensor surfaces are exposed in feral position and are optimised for UV and physical protection
- thick skin is present on sole and palms and is optimised for grip and resist abrasion

Question 4

What is the structure and function of the epidermis layers?

Answer 4

Structure
- stratified squamous epithelium, made of keratinocytes mostly, which produce keratin, which is a fibrous, structural protein.
Layers:
Stratum Corneum: corny corpses
Stratum lucidum: thick skin only, locked losing
Stratum granulosum: grainy, greasy
Stratum spinosum : spiny, sticky, strength and surveillance
Stratum basale: birth and busy
Function:
- UV protection, Physical protection vit D synthesis

Question 5

Describe the st. Corneum

Answer 5

Flat, dead, keratin filled keratinocytes
- physical and UV protection
Surrounded by extra cellular lipid matrix
- permeability and water loss barrier
Provides grip
Made up of corneocytes - dead keratinocytes.

Question 6

Describe st lucidum

Answer 6

Locked, losing
Only in thick skin
Very flat keratinocytes, already dead and disintegrating

Question 7

Describe st granulosum

Answer 7

Grainy, greasy
Keratinocytes producing granules
- keratohylin granules - cause cell degradation and nucleus disintegration
Lamellar granules - secrete lipid for water loss barrier - greasy

Question 8

Describe st spinosum

Answer 8

Spiny, sticky, strength and surveillance
Keratinocytes producing keratin
Firmly connected by desmosomes
Contain langerhans cells for immune response

Question 9

Describe st basale

Answer 9

Keratinocytes constantly dividing from stem cells
Single layer in basement membrane
Merkel cells for touch sensation
Melanocytes make and distribute melanin

Question 10

Describe the structure and function of the dermis

Answer 10

Papillary layer:
- comprised of dermal papillae, the bumpy bits
- fibroblasts for synthesis of ct
- immune cells
Reticular layer:
- collagen fibres, strength and structure
- elastin fibres , elasticity and stretch
- gags, bind water for movement, shock absorption and compressibility
Other components:
- blood vessels from and to hypodermis
- lympathic vessels from dermal papillae
- nerves
- hair follicles, sebaceous and sweat glands, nails

Question 11

Describe hypodermis structure and functions

Answer 11

• Superficial fascia, loose connective tissue and adipose tissue, nerves, vessels, lympathics
• Functions as an energy reservoir, thermal regulation, cushioning, skin movement and physical appearance
• Also helps in wound repair and regeneration as it supplies blood, and lympathics for nutrients and immunity

Question 12

What are the structures in skin that protect against UV?

Answer 12

• Corneocytes provide a physical barrier
• Melanocytes make and distribute melanin which acts as a protective cap to the keratinocytes in the st basale
• epidermal thickening in UV exposure

Question 13

Describe how the skin layers are involved in thermoregulation

Answer 13

Epidermis: direct heat transfer at surface from blood vessels - constriction and dilation
Dermis: evaporative heat loss through sweat glands
Hypodermis; heat conservation, insulation and goose bumps via hair follicles

Question 14

what are the skin’s functions in wound repair?

Answer 14

• Stem cells increase in divisions -n.b. epidermal invaginations
• dermal immune cells: tissue repair and healing
• fibroblasts increase in activity: tissue renewal and scars
• vascular network and fibroblasts

Question 15

what can Uv radiation cause for the skin?

Answer 15

> skin ageing features
leathery skin - thickened epidermis, elastin clumping
damage of collagen and elastin fibres
immunosuppression
decrease in antioxidants and increase in oxidative damage
decrease folate stores and DNA damage
skin cancer

Question 16

describe what happens during a first degree/ superficial burn. Symptoms and its effect of homeostasis

Answer 16

> damage restricted to epidermis
symptoms
- redness -> increased blood flow in response to injury
- inflammatory reaction -> oedema (swelling) associated with increased blood flow, then loss of fluid from blood vessels into the extravascular space
- pain -> associated with stimulation of free nerve endings
effects homeostasis via dehydrations

Question 17

describe what happens during a deep partial burn. Symptoms and its effect of homeostasis

Answer 17

> both dermis and epidermis are affected
symptoms:
- redness, odema, pain
- blistering: loss of epithelium with fluid accumulations between layers of skin
causes dehydration, hypothermic initially, hyperthermic later

Question 18

describe what happens during a full thickness burn. Symptoms and its effect of homeostasis

Answer 18

> damage is through to the hypodermis
symptoms:
- white or charred, leathery skin- fat in the adipose tissue is burnt
- significant oedema and increase fluid loss -> blood and lymph vessels lost , therefore nothing ot take away fluid so it just leaks out
- little senstation, nerve endings burnt away
- infection, no barrier to external env. and no immune cells or immune system to monitor conditions
- disfigurement and tissue loss
causes sign. dehydration, hypotension, tachycardia ( increased HR due to los bp and pain), hypothermia.