Inflammation and wound healing Flashcards
What is a wound?
A wound is a breakdown in the protective function of the skin (loss of continuity of epithelium)
What are the five components of inflammation?
Redness Swelling Pain Heat Loss of function
what is the aim of inflammation?
To expel foreign body/infection if present
Structural and functional repair
Describe briefly what causes each clinical feature of inflammation?
Redness: small blood vessel dilation
Swelling: Fluid in extracellular matrix
Pain: stretching of skin due to oedema, mediators such as bradykinin and serotonin stimulate pain receptors.
Heat: increase in blood flow to the area due to vasodilation and fever
LOSS of function: movement inhibited by pain and swelling immobilises area.
What are possible outcomes of inflammation?
Resolution
Scar
Abscess via liquefactive necrosis = transformation of tissue into liquid viscous mass
Chronic inflammation
What effect does vasodilation have on vessels?
It increases their permeability and allows emigration of plasma components and cells.
List 6 vasoactive mediators
Histamine Prostaglandin C3a C5a Bradykinin Cytokines
Name 2 vasoactive mediators
Serotonin - found in platelets
Histamine - abundant in granules in mast cells
What does bradykinin achieve?
Vasodilation
Pain
What do arachidonic acid metabolites produce?
Leukotrienes
Prostaglandins
Thromboxane A2
What is the main function of nitric oxide?
Vasodilation
Outline the process of cell infiltration to an inflammatory site
Rolling adhesion
Tight Binding
Diapedesis
Migration
What is found on the surface of endothelial cells which the WBC/leukocytes bind to?
P and E selectin
What do monocytes differentiate/mature into as they move from the bloodstream into tissue?
Macrophages
Which cell is key in activating an adaptive response?
Dendritic cell
what are the 3 phases of wound healing?
Inflammation
Proliferation
Remodelling/maturation
describe the inflammatory phase of wound healing
Platelets initiate Haemostasis to limit blood loss and allow blood clotting
Wound site become red, warm and swollen. This is due to increased vasodilation which also increases the permeability of blood vessels so that plasma contents and cells may migrate easily.
Chemokines, cytokines and growth factors stimulate the migration of neutrophils to arrive at the injury site first. Macrophages also arrive at the injury site. They also send out signals for more cells to migrate.
Bacteria and debris is removed by neutrophils and macrophages via phagocytosis. Neutrophils have a short half-life and die quick to form pus. Macrophages remove them too.???
How long doe she inflammatory phase last?
24-48 hours
describe the proliferative stage of wound healing
Epidermal Growth factors stimulate epithelial cells to loosen their desmosome adhesions to allow keratinocytes to migrate to the wound site. The cells cover the site in a single layer of keratinocytes to cover granulation tissue.
Once granulation tissue is covered, keratinocytes proliferate to produce more epithelial cells. Granulation tissue is formed and it consists of type III collagen.
PD Growth factors attract fibroblasts to the site and they synthesise the ECM and produce MMPs.
Endothelial cells undergo angiogenesis to repair blood vessels and deliver oxygen to cells to allow wounds to heal.
describe the remodelling stage of wound healing
Granulation tissue is replaced with mature scar tissue.
Collagen is organised into thick, parallel bundles and cross linked to form a mature scar.
Tissue collagen is replaced with type I collagen.
What ever of tissue strength is restored?
70-80% of tissue strength is restored to pre-injury strength
What are local factors that may effect wound healing?
Oxygenation
Infection
Vascular supply
Foreign body
What are systemic factors that may effect wound healing?
Age Obesity Alcohol and Smoking Mediations e.g. Corticosteroids Diseases e.g. diabetes
What are interleukin 1, 6 and TNF alpha involved in ?
Inflammation
