Acute inflammation Flashcards
What are the 5 cardinal signs of inflammation?
- Reddening - increased blood flow to area (hyperaemia due to dilation of capillaries)
- Swelling - exudation of fluid from dilated blood vessels into inflamed tissue
- increased heat - increased blood flow
- pain - due to chemical mediators and local pressor on nerve endings from exudate
- loss of function
What are the stages of acute inflammation?
- vascular phase
- exudative phase
- migration of leucocytes
What is the vascular phase?
Initial phase = transient (secs)
- arteriole constriction (‘white line’)
- smooth muscle response
Hyperaemia = (mins - days)
- arteriole and capillary dilation
- key chemical mediators are prostaglandins, endothelin and nitric oxide
What is the exudative phase>
Increased vascular permeability due to endothelial cell contraction, which is caused by histamine released by mast cells
Caused by:
Direct endothelial injury
Physical damage
Toxic agents
Infection
Enzymes
Oxygen free radicals
Result - escape (exudation) of protein-rich fluid from blood into surrounding tissue
Contents of fluid exudate
Water and electrolytes
Plasma proteins (albumin, globulin, fibrinogen)
Red blood cells
Platelets
What is the migration of leucocytes stage?
a) Margination / Pavementing
altered blood flow & loss of axial stream
expression of adhesion molecules (e.g. selectins, integrins)
b) Chemotaxis
Neutrophils move along a chemotactic gradient at ~2mm per hour, macrophages are slightly slower
Chemotaxins that attract & activate leukocytes:
bacterial products e.g. endotoxin
fibrin degradation products
complement derived factors
cytokines esp. lymphokines
tissue breakdown products
c) Emigration via intercellular junctions
motile cells force an opening
basement membrane is breached
What do neutrophils do in acute inflammation?
formed in the bone marrow
production time 7 days - half life in blood 6 hours
replaced twice a day
once they enter tissues do not return to the blood - most are lost through the mucous membranes of the body: gut, urinary and respiratory tract
have multilobed nuclei and fine cytoplasmic granules
- Phagocytosis of microorganisms or foreign material and fusion of phagosome with lysosomes to kill or degrade material
- Secretion and/or release of granules into exudate to enhance acute inflammatory response
How are neutrophils recruited?
- Neutrophils marginate in venules & capillaries
- Loosely adhere to endothelium and roll along inner blood vessel wall (mediated by selectins)
- At junction between endothelial cells, firmly adhere and emigrate from blood vessel into tissue (mediated by integrins)
- Migrate to site of damage along a chemotactic gradient
What do eosinophils do in acute inflammation?
- formed in the bone marrow, similar life span to neutrophils
- impart a greenish colour to the tissue
- have bilobed nuclei and distinct granules in the cytoplasm
- are prominent in parasitic infections, and local allergic reactions [IgE]
What do mast cells do in acute inflammation?
-heavily granulated mononuclear cells found in tissues
-tissue lifespan 4-12 weeks depending on location
-degranulate in tissue injury, releasing histamine, heparin, and 5-hydroxytryptamine (serotonin) – chemical mediators of vasodilation, chemotaxis and pain
-critical in initiation of acute inflammatory response
What are basophils?
also formed in the bone marrow
multilobed nucleated cells with large bluish granules in the cytoplasm
granules similar to those of both neutrophils and mast cells
important in IgE mediated injury to tissues (allergic reactions)
What are 5 different pyrogens?
Pyrogens act on the temp control centres in the hypothalamus of the brain to raise body temperature
1. Neutrophils - prime source when they begin to phagocytose, also eosinophils and macrophages
2. Gram-negative organisms - their cell walls contain pyrogens
3. Damaged tissue cells - necrosis releases pyrogens
4. Antigen-antibody complexes - may release pyrogens
5. Tumours - may release pyrogens particularly those which have metastasised - also the pyrexia caused by the central necrosis in such tumours
What is a summary of the sequence of events in acute inflammation?
- Momentary vasoconstriction of the blood vessels in affected area
- Dilation of the blood vessels
- Exudation of fluid, rich in protein, into the tissues (effusion)
- Margination of leukocytes
- Emigration of leukocytes through the altered endothelium
- Induction of increased temperature
What are the functions of inflammatory effusion?
dilutes the agent
contains antibodies - which attack or coat (opsonise) the agent and facilitate phagocytosis by neutrophils and macrophages
may contain fibrin which immobilises the agent and provides a matrix for migration of inflammatory cells
contains chemotaxins that attract more inflammatory cells to the site
washes away the agent - if on a surface, e.g. skin and alimentary tract
brings the agent via the lymphatic vessels to the local lymph nodes - for further processing or antigen presentation
What are the fluid types?
serous
catarrhal
fibrinous
diphtheritic
haemorrhagic
purulent
What is serous inflammation?
Due to mild vascular injury in an organ or in vessels underlying a surface
- a clear to cloudy fluid with little protein present
- vesicles of the skin produce a serous fluid; many inflammations in joints are serous
Sequel - resolves when the irritant is overcome, or may progress to a more serious reaction
