PMI03-2012 Acute Inflammation Flashcards
What is acute inflammation?
The initial response taking place in the minutes and hours following injury
What is chronic inflammation?
Persistent inflammation taking place alongside attempts at healing
What are the functions of acute inflammation?
Carriage of fluid, proteins and cells from local blood vessels to damaged areas
Destruction of the causative agent driving the inflammation through the dilution of toxins and entry of leukocytes
Removal of damaged tissue from the site and initiation of repair
Initiation of repair through fibrin formation and transport of nutrients and drugs
What are the two events of the vascular phase?
Vasodilation and increased Vascular permeability
What process initiates acute inflammation?
vasodilation
What occurs during the vasodilation process?
Vasodilation results form the direct action of smooth muscle cells and endothelial cells
Due to tissue damage, histamine, prostaglandins, platelet activating factor and kinins are released
How does vasodilation affect the flow rate?
Decreases the flow rate, causing vascular congestion
This leads to heat, redness, swelling and pain at the site of injury
What are the effects of increased vascular permeability?
There are gaps between the endothelial cells opening, which results in the leakage of fluid and plasma proteins into the extra vascular space
How does increased vascular permeability arise?
Due to the release of histamine, leukotrienes, platelet activating factors and kinins
What is exudation?
The process by which there is net flow of fluid and plasma proteins from within the vessel into the EVS
What is the fluid exudate?
The fluid that collects in the EVS
What normally occurs in the EVS in terms of hydrostatic pressure?
There is increased hydrostatic pressure in the EVS at the venous end, which forces fluid back into the vessel and there is no net gain of fluid into the EVS
What occurs during acute inflammation to the EVS?
There is increased vascular permeability at the venous end, which leads to increased osmotic pressure at the EVS so there is a net flow of fluid in the EVS resulting in fluid exudate
What is margination?
At sites of inflammation, neutrophils are found towards the edges closer to the endothelial cells
How do the neutrophils attach to the endothelial cells in acute inflammation?
As neutrophils marginate, they are able to detect ligands on endothelial cells
There is a weak bond between the selectins of neutrophils and endothelial cells
A process of attachment and detachment occurs
As a result, neutrophils roll across the endothelial surface in a process called rolling
Rolling ends when the neutrophil becomes firmly attached to the endothelial cell, which is brought about by the expression of integrins on the neutrophils which bind to ICAM-1 on the endothelial cell
What group of receptors are important in the cellular events?
Selectins
P-selectin on endothelial cells
L-selectin on neutrophils
What are the selectins upregulated by?
The selectin receptors are upregulated by IL-1 and TNF, which are expressed as a result of tissue damage
What occurs after attachment of neutrophils to endothelial cells?
The neutrophil squeezes through the endothelial cell and into the fluid exudate
The neutrophils act as the cellular component of the fluid exudate
Once the neutrophils enter the fluid exudate, it migrates to the site where it is most needed by attraction by bacterial products, chemokine, C5a and leukotriene B4 in a process called chemotaxis
How do neutrophils act?
Attachment and phagocytosis
Production of reactive oxygen intermediates (respiratory bursts)
Production of inflammatory mediators
What is a respiratory burst?
A rapid release of reactive oxygen species by neutrophils and monocytes
These are released on contact with pathogens and are important in the degradation of internalised bacteria and fungi
What are cardinal signs of inflammation?
Heat, redness, swelling, pain and loss of function
What are the beneficial effects of acute inflammation?
Dilution of toxins Entry of antibodies Transport of drugs Fibrin formation Transport of nutrients
What are the adverse effects of acute inflammation?
Tissue damage
Swelling
Pyrexia (fever)
