Acute Inflammation Flashcards
What is acute inflammation?
Response of living tissue to injury, innate, immediate and early, short duration
(Initiated to limit tissue damage)
Put simply what happens during acute inflammation?
There are vascular and cellular reactions controlled by chemical mediators whose primary function is to protect the tissue, but there can be complications
Name some causes of acute inflammation?
Infections (bacterial, viral, parasitic) and microbial toxins
Hypersensitive reactions
Physical and Chemicals agents (thermal injury=burns/frostbite, radiation)
Tissue necrosis
Foreign bodies
Trauma (blunt and penetration)
What are the clinical features of acute inflammation?
Rubor (redness) Tumor (swelling) Dolor (pain) Calor (heat) Loss of function
What are the 3 changes in tissue that occur during acute inflammation?
- changes in blood flow (vascular phase)
- exudate of fluid into tissue
- infiltration of inflammatory cells (cellular phase)
(*there are inflammatory mediators of each step)
What are the changes in blood flow that happen during an acute inflammatory response? (4)
- transient vasoconstriction of arterioles
- vasodilation of arterioles (and capillaries)=calor and rubor
- increased permeability of blood vessels=exudate of protein rich fluid into tissues + slowing of circulation (tumor)
- stasis (increased viscosity of blood)
Name a chemical mediator involved in the immediate response during an acute inflammation
Histamine
What role does histamine play in an acute inflammatory response?
- causes vascular (arteriolar) dilation
- causes transient increase in vascular permeability (venular leakage) - histamine causes endothelial cells to contract and pull apart
- causes pain
serotonin has vascular effects similar to histamine
What is histamine?
Chemical mediator-vasoactive amines (another one of which is serotonin)
Stored in granules in mast cells/basophils/platelets -(where serotonin is also stored)
Released in response to many stimuli ie physical damage, immune reactions and complement components
Name some other chemical mediators like histamine involved in the first stages of acute inflammation
Serotonin
Prostaglandins
Leukotrienes
Brandykinins
Why is abundant fluid in the tissue a good thing, what is the function of it?
Excess fluid drains from the tissues into the lymphatic taking with it micro-organisms and antigens which are thus presented to the immune system within the lymph nodes
What are the 3 main types of defensive proteins in the exudate during an acute inflammatory response?
Opsonins
Complement
Antibodies
What do opsonins do?
Coat foreign materials and make them easy to phagocytose
What do complement proteins do?
Assemble locally to produce a bacteria-perforation structure
What do antibodies do?
Bind to the surface of micro-organism and also act as opsonins
Why is the tissue fluid in inflammation called an exudate?
Because it is protein rich
In acute inflammation is there a net flow of fluid in or out of the blood vessels? Why?
Out of vessels
Because arteriolar dilation leads to increase in hydrostatic pressure and increased permeability of vessel walls leads to loss of proteins into interstitium
What is the difference between a transudate and an exudate and what is the significance of this in terms of inflammation?
Transudate- fluid loss due to hydrostatic pressure imbalance only, tissue fluid has low protein content
Exudate- fluid loss in inflammation- tissue fluid has a high protein content
Knowing this we can tell the difference between oedema caused by inflammation (exudate) or something else ie cardiac failure(transudate)
What are the mechanisms of vascular leakage in acute inflammation? What chemical mediators cause these changes?
- Endothelial contraction- histamine, leukotrienes
- Cytoskeleton reorganisation- cytokines IL-1 and TNF
- Direct injury (toxic burns, chemicals)
- Leukocyte dependent injury-toxic oxygen species and enzymes from leucocytes
- Increased transcytosis (process by which fluid moves through cells)- channels across endothelial cytoplasm- VEGF
What are the chemical mediators that induce vascular leakage in acute inflammation?
Histamine (mast cells/basophils/platelets)
Serotonin (mast cells/platelets)
Brandykinin (from plasma precursor)
Complement components- C3a, C4a, C5a (from plasma precursor)
What is the primary type of cells found in acute inflammation?
Neutrophil (presence indicates the invasion of bacteria/parasites/tissue injury)
What are the 6 stages a neutrophil dealing with acute inflammation must complete?
Chemotaxis Activation Margination Diapedesis Recognition-attachment Phagocytosis
What is chemotaxis in acute inflammation?
The process by which a neutrophil is summoned to a place of injury in response to a chemotaxin (bacterial product, injured tissues, substances produced by leucocytes and spilled blood-clotted)
Movement along concentration gradients of chemoattractant
Give an example of a bacterial chemotaxin
Endotoxin
Lipopolysaccharide from the outer membrane of gram negative bacteria
What produces leukotrienes?
Leucocytes
What is ‘activation’ of neutrophils in acute inflammation?
Reorganisation of the cell’s cytoskeleton as a result of Na+ and Ca2+ influx (+swelling)
Cell produces pseudopod.
Cell becomes sticker
What is ‘margination’ of neutrophils in acute inflammation?
Process by which leucocytes stick to the endothelial lining, (caused by stasis- slow blood flow)
Become trapped when their receptors bind to adhesion molecules (integrins-adhesion/selectins-for rolling along)
What is ‘diapedesis’ in acute inflammatory responses?
-crawling through the membrane- do not use the endothelial gaps .
Leucocytes produce collagenase which digests the basement membranes
(Also called emigration)
What is ‘recognition-attachment’ of leucocytes in an acute inflammatory response?
Recognising the bacterium and attaching to it- made easier by opsonins (ie IgG antibodies and C3b complement component)