Histology Flashcards
Where is inflammatory infiltrate seen in acute dermatitis?
In the upper dermis
Describe inflammatory infiltrate in acute dermatitis
Groups of purple cells which will be lymphocytes, seen in the upper dermis
Where is the main abnormality in acute dermatitis and what is seen?
Main abnormality is in the epidermis where bubble-like structures will be seen. These represent fluid collections and would clinically be seen as tiny blisters
Spongiosis
Fluid accumulation between the keratinocytes in the epidermis
True or false: spongiosis is the typical histological pattern seen in acute dermatitis
True
Epidermis in psoriasis
Thickened epidermis and lots of keratin in the keratin layer which is loosely packed, with the accumulation of inflammatory cells, particularly neutrophils
Where are nuclei normally broken down?
Granular layer
Parakeratosis
Retention of nuclei
In which condition is parakeratosis present and why?
Psoriasis due to rapid and abnormal differentiation of keratinocytes
Describe rete pegs in psoriasis
They are thicker and longer and often joined together
Histology of bullous pemphigoid
Epidermis splits up off the dermis at the dermo-epithelial junction so the whole of the epidermis forms the roof of the blister. If split is higher up then the roof is thinner and blister bursts more easily
Inflammatory cells within the blister – mostly eosinophils
Toxic dermal necrolysis is drug induced - true or false?
True
What type of cell dies in toxic dermal necrolysis?
Keratinocyte
Mortality rate with toxic dermal necrolysis?
25-40%
What does toxic dermal necrolysis result in?
Epidermal detachment from dermo-epidermal junction
What can skin failure lead to?
Loss of thermoregulation, increased risk of infection, failure of homeostatic function
Things required for healthy skin
Intact physical barrier
Functioning immune system
Functional vasculature
Functioning venous return and lymphatic system
Means of temperature regulation
Normal sensory nerve function to warn us about injury
Adequate nutrition
Means of temperature regulation in healthy skin
Capillary dilation/constriction, functioning sweat glands
What is a wound?
Any break in the skin
What does the method of wound healing depend on?
Size and type of wound
How do most surgical wounds heal?
Primary intention
Primary intention healing
Edges approximated by stitches leading to rapid healing
How can primary intention healing be compromised?
Haematoma, infection, poor suture technique, dehiscence
What type of wounds is secondary intention healing used for?
Larger wounds that are too tight to stitch or where direct closure would cause significant distortion of surrounding tissues
3 stages of secondary intention healing
1 = inflammation 2 = proliferation 3 = tissue remodelling
What happens in inflammation stage of secondary intention healing?
Platelets form an initial clot and release inflammatory mediators.
Leucocytes debride the wound bed by phagocytosing bacteria and scavenging cellular debris
Inflammation gradually decreases and keratinocyte proliferation and new tissue formation becomes predominant
What happens in proliferation stage of secondary intention healing?
Cells proliferate to re-epithelialise the wound surface
Granulation tissue formation is stimulated
Fibroblasts lay down matrix and contract the wound (fibroplasia)
Endothelial cells develop new blood vessels (angiogenesis)
What happens in tissue remodelling stage of secondary intention healing?
New tissue is converted into mature scar tissue over a period of months
Fibroblasts lay down collagen to improve the tensile strength of the scar and restore the dermal matrix
Superficial burns are erythematous/non-erythermatous, wet/dry and non-painful/painful
Superficial burns are erythematous, wet and painful
What colour are deep burns?
White or black and charred
Are deep burns wet or dry?
Dry
Are deep burns painful?
No, they are numb
Where do the burns extend in:
- First degree?
- Second degree/partial thickness?
- Third degree/full thickness?
First degree = epidermis only
Second degree/partial thickness = epidermis and dermis
Third degree/full thickness = beyond dermis
What are chronic wounds?
Wounds present >6 weeks
What do chronic wounds often exhibit?
Surface slough
What is surface slough?
A mixture of dead cells, polymorphs and bacteria. It is a yellow/green colour
Effect of slough on healing of wounds
Inhibitory effect on healing ability of wound
How can slough be removed?
Chemically, with physical debridement or larval therapy
Where do chronic wounds tend to heal from?
The edges - increased risk of infection
Factors that contribute to delayed healing of wounds
Infection Poor arterial supply Impaired venous return Repeated trauma/friction Poor nutritional state Underlying systemic disease
Factors leading to breakdown of skin: erosion and ulceration (relating to pressure sores)
Prolonged pressure over a bony area
Lack of blood flow
Friction from bedding/clothing
Irritation from sweat/blood/urine/faeces
Stages of development of pressure sores
- Skin is unbroken but shows a pink or reddened area. May look like a mild sunburn. Skin may be tender, itchy or painful
- Skin is red, swollen and painful. Blisters (broken or intact) may be present. Upper layers of skin begin to die
- Sore has broken through the skin and wound extends down to deeper layers of the skin tissue. Crater-like ulcers are present. Wound is prone to infection
- Sore extends past the skin and into fat, muscle and bone tissue. Blackened, dead tissue called eschar may be seen in deep opened wounds
