Skin Flashcards
What is the role of the epidermis?
Replace damaged cells and protect from UV radiation
What happens in the Stratum basale?
Keratinocytes dividing and push older cells up
Melanocytes contain melanin which absorbs UV radiation
What happens in the Stratum spinosum?
Anchors cells together by interlocking cytoplasmic processes - prickle cells
What happens in the Stratum granulosum?
Enzyme induced destruction of cells
Lipid rich secretion acts as water sealant
Keratin = further meshing
What happens in the Stratum corneum?
Dead cells which are flattened and filled with densly packed keratin (corneocytes)
Corneocytes are shed from the skin
What is the function of the dermis?
Strength and elasticity
(collagen, fibroblasts, elastin)
Contains specialised structures
What is the function of the hypodermis?
Cushions and insulates tissue below
What are the functions of the skin?
Production of vitamin D
Sensory organ for touch, pain and temperature
Controls body temperature
Barrier to protect tissue and organs
How does vitamun D raise plasma calcium levels?
Stimulates intestinal epithelium to produce more carrier proteins for Ca.
What are the names of the sensory receptors in the skin?
Machanoreceptors - pressure/touch
Thermoreceptors - temp
Nociceptors - pain
How does the skin control temperature?
Vasodilation and vasoconstriction of capillaries
Sweat glands secrete water and salt when >37 degrees in the body
Mitochondria oxidise brown fat to produce heat
What does the skin act as a barrier to protect from?
Bacteria and toxins
Dehydration
UV radiation
Mechanical damage and trauma
What are the four phases of skin healing?
Haemostatis
Inflammatory phase
Proliferative phase
Maturation phase
Describe Haemostasis
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
Describe the inflammatory stage:
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
Describe the proliferative stage
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
Describe the maturation stage
Collagen re-aligned to improve strength and pull wound inwards
Extra blood vessels closed
Scar formed (can take 2 years)
Which intrinsic patient factors affect the healing process?
Patient nutrition Skin perfusion Age Weight Co-morbidities and Medication Smoking
Which extrinsic wound factors affect the healing process?
Moist wound Wound temperature at 37 degrees Tissue oxygenation pH Infection delays wound healing Clean wound surface
