Acute Inflammation 1 Flashcards
What is the definition of acute inflammation?
A dynamic homeostatic mechanism which involves a series of protective changes occurring in living tissue as a response to injury.
What is a cutaneous abscess?
A localised collection of pus in the skin.
What are the cardinal signs of inflammation?
Rubor - redness Calor - heat Tumour - swelling Dolor - pain Loss of function
Give possible aetiologies for acute inflammation.
Microorganisms (bacteria, fungi, viruses, parasites)
Trauma (injury to tissue - all injuries, even sterile)
Chemical (upset pH, bile and urine (irritation if in wrong place)
Heat (sunburn), cold (frostbite), ionising radiation
Dead tissue (cell necrosis irritates adjacent tissue)
Hypersensitivity
Where does acute inflammation take place?
It is localised to affected tissue and takes place in the microcirculation.
What is the microcirculation?
Capillary beds (fed by arterioles/drained by venues) Extracellular 'space', lymphatic channels + drainage
What kind of forces control flow (fluid flux) across the membrane?
Hydrostatic and colloid osmotic pressures and compartments and physical constants.
What is hydrostatic pressure?
The pressure exerted by blood on the blood vessel walls, so as blood moves through the capillary fluid leaks out the pores and the ‘blood pressure’ decreases as it moves from the arterioles to the venules.
What is colloid osmotic pressure?
A form of pressure exerted by the proteins in blood (mostly albumin) that pulls water from the ISF into the plasma.
(Plasma proteins can’t cross capillary walls so water moves from ISF to plasma by osmosis)
What happens to blood vessels in acute inflammation?
There are changes in vessel radium which affect flow
Changes in permeability of vessel wall affecting exudation
Movement of neutrophils from vessel to extravascular space
What are the immediate local changes in vessel radius and blood flow straight after injury?
- transient arteriolar constriction (protective)
- local arteriolar dilation (active hyperaemia)
- relaxation of vessel smooth muscle
What does increased arteriolar radius cause?
Increased tissue blood flow, resulting in redness and heat. A minute increase in radius will result in a massive increase in flow.
What is the increased permeability of the local blood vessels largely due to?
Locally produced chemical mediators.
What are the effects of increased permeability of vessel walls?
Net movement of plasma from capillaries to extravascular space (exudation)
What is an exudate?
The substance that exudated (leaked) out of the capillary into the extravascular space.
It is rich in protein, plasma and includes immunoglobulins and fibrinogen.
