Skin

Question 1

What is the role of the epidermis?

Answer 1

Replace damaged cells and protect from UV radiation

Question 2

What happens in the Stratum basale?

Answer 2

Keratinocytes dividing and push older cells up

Melanocytes contain melanin which absorbs UV radiation

Question 3

What happens in the Stratum spinosum?

Answer 3

Anchors cells together by interlocking cytoplasmic processes - prickle cells

Question 4

What happens in the Stratum granulosum?

Answer 4

Enzyme induced destruction of cells
Lipid rich secretion acts as water sealant
Keratin = further meshing

Question 5

What happens in the Stratum corneum?

Answer 5

Dead cells which are flattened and filled with densly packed keratin (corneocytes)
Corneocytes are shed from the skin

Question 6

What is the function of the dermis?

Answer 6

Strength and elasticity
(collagen, fibroblasts, elastin)
Contains specialised structures

Question 7

What is the function of the hypodermis?

Answer 7

Cushions and insulates tissue below

Question 8

What are the functions of the skin?

Answer 8

Production of vitamin D
Sensory organ for touch, pain and temperature
Controls body temperature
Barrier to protect tissue and organs

Question 9

How does vitamun D raise plasma calcium levels?

Answer 9

Stimulates intestinal epithelium to produce more carrier proteins for Ca.

Question 10

What are the names of the sensory receptors in the skin?

Answer 10

Machanoreceptors - pressure/touch
Thermoreceptors - temp
Nociceptors - pain

Question 11

How does the skin control temperature?

Answer 11

Vasodilation and vasoconstriction of capillaries
Sweat glands secrete water and salt when >37 degrees in the body
Mitochondria oxidise brown fat to produce heat

Question 12

What does the skin act as a barrier to protect from?

Answer 12

Bacteria and toxins
Dehydration
UV radiation
Mechanical damage and trauma

Question 13

What are the four phases of skin healing?

Answer 13

Haemostatis
Inflammatory phase
Proliferative phase
Maturation phase

Question 14

Describe Haemostasis

Answer 14

Stop bleeding
Platelets recognise exposed collagen and releas TA2 causing platelet aggregation with collagen in vessel wall - temporary plug
Activated platelets release serotonin reducing blood supply around the wound
Damaged tissue releases thromboplastin which combines with calcium to form insoluble fibrin - clot forms

Question 15

Describe the inflammatory stage:

Answer 15

Langerhans have released inflammatory mediators:
Bradykinin = pain
Leukotrines = blood flow at wound causing warmness
Increase in vascular permeability - redness and WBC to the wound causes inflammation
WBC = Neutrophils - digest bacteria and particles
Monocytes move towards and mature into macrophages which continue

Question 16

Describe the proliferative stage

Answer 16

Macrophage role
Low oxygen - release angiogenic growth factors - devlop new blood vessels - bring oxygen and nutrients
Releases chemicals to attract granulation tissue - produces new connective tissue
Fibroblasts activates - produce collagen network
Myofibroblasts (specislised fibroblasts) contract edges of the wound
Epithelial cells move over the top - stop due to contact inhibition

Question 17

Describe the maturation stage

Answer 17

Collagen re-aligned to improve strength and pull wound inwards
Extra blood vessels closed
Scar formed (can take 2 years)

Question 18

Which intrinsic patient factors affect the healing process?

Answer 18

Patient nutrition
Skin perfusion
Age
Weight
Co-morbidities and Medication
Smoking

Question 19

Which extrinsic wound factors affect the healing process?

Answer 19

Moist wound
Wound temperature at 37 degrees
Tissue oxygenation
pH
Infection delays wound healing
Clean wound surface