3 - Acute Inflammation Flashcards
What is inflammation?
The response of living tissue to injury
What are the characteristics of acute inflammation?
- Eary transient response to cell injury in live vascular tissue, e.g cannot have inflammation in cartilage
What causes inflammation?
- Physical trauma
- Physical and Chemical agents
- TIssue necrosis
- Immune reactions
- Foreign bodies
- Infections and toxins
- Hypersensitivity
What are the clinical signs of acute inflammation?
What are the two different phases in acute inflammation?
1. Vascular - to form exudate via changing blood flow and fluid entering tissue
2. Cellular - response to get cells to the scene
What is the first stage of inflammation?
Vascuar phase - changes in blood flow
1. Initial vasoconstriction (s)
2. Vasodilataton (mins) (heat and redness)
3. Permeability increase so oedema
4. Red cell stasis due to more viscous blood
How does vasodilatation occur?
Due to vasoactive mediators like histamine, which is a vasoactive amine
What are vasoactive amines?
Group of chemical mediators that are involved in early inflammation, e.g histamine and serotonin. They are stored in granules of basophils, mast cells and platelets (serotonin), and released in response to stimuli like damage
Cause: Increased venular permeability, pain, arteriolar dilatation
How does fluid move from in the blood into the interstitium?
- Vasodilatation increases the hydrostatic pressure in the capillary as blood flow increases, forcing out
- Increased vessel permeability leads to leakage of proteins so increased interstitial oncotic pressure
STARLINGS LAW
Why does inflammation lead to stasis?
Fluid is leaving the capillary so decreased fluid in capillary, increased haematocrit so increased viscosity and decreased flow through vessel
What are the different types of interstital fluid?
Exudate: In inflammation due to increased vascular permeability
Transudate: Low protein fluid due to increase hydrostatic pressure or decreased oncotic pressure, e.g heart failure, hepatic failure or renal failure (excretion of plasma proteins)
How can there be increased vascular permeability?
- Endothelial contraction: histamines, leukotrienes, bradykinin
- Direct injury: burns
- Leucocyte dependent injury: respiratory bursy
- Endothelial skeleton reorganisation: cytokines, TNF
What will a tissue sample look like under the microscope during acute inflammation?
Lots of neutrophils
What does it mean if neutrophils are found in the tissues?
Normally only in blood/bone marrow so in tissue indicates infection by parasite, bacteria etc
How do neutrophils get from the blood to killing bacteria in the tissues?
- Chemotaxis
- Activation
- Margination
- Diapedesis/Emigration
- Recognition-attachment to bacteria
- Phagocytosis
What is chemotaxis and what are some chemotaxins?
Directional movement towards a chemotaxin, up a concentration gradient.
Chemotaxins:
- Leucocytes: LTB4
- Bacterial peptides/Endotoxins
- Complement release fragments especially C5a
- Clotted blood due to thrombin and FDP’s
How does activation of neutrophils occur?
Chemokine binds to receptor on neutrophil causing massive influx of Na and Ca so it swells and reorganises it’s cytoskeleton into triangle towards stimulus. Puts out pseudopodia and cell becomes stickier
How does a neutrophil adhere to endothelial cells?
Selectins: On endothelial surface, upregulated with chemotaxins
Integrins: On neutrophil surface and bind to selectins. Binding of PAF receptor increases affinity of integrins by activating them
How does diapedisis occur?
Leucocytes produce collagenase to break down basement membrane of endothelial cells so they can fit in. Once in tissue, move along collagen fibres
What is opsonisation and how does it aid phagocytosis?
Plasma proteins that cover targets making it easier for phagocytes to recognise them e.g IgG antibody (reinfection) and C3b fragment of complement
If no opsonins phagocyte recognising surface antigens