Flashcards in Session 2 -> Acute inflammation Deck (97):
What is acute inflammation?
-The immediate, innate and stereotyped response of living tissue to any injury
-It is usually short in duration and involves both vascular and cellular reactions
What controls acute inflammation?
-Chemical mediators, mostly from plasma but some from cells
List the main causes of acute inflammation
-Hypersensitivity immune reactions
-Physical agents (Heat/UV/Knife)
What are the main cardinal signs of acute inflammation?
-Loss of function
How does loss of function act as a protective mechanism?
-Enforces rest and prevents further injury
Describe the changes in vascular flow which occurs with acute inflammation
-Transient vasoconstriction then local vasodilation, resulting in increased bloodflow and then vascular stasis
What is the consequence of local vasodilation in acute inflammation?
-Increased stasis results in an increased hydrostatic pressure which causes oedema
Apart from increased hydrostatic pressure, what other factor of acute inflammation contributes to oedema?
-There is increased vascular permeability which means plasma proteins leak into the interstitium, reducing colloid oncotic pressure-> less water is drawn back into the blood vessel causing oedema
Why does vascular stasis occur in acute inflammation?
-Decreased colloid oncotic pressure -> reduced fluid resorption
-Increased hydrostatic pressure -> increased fluid loss
-Blood becomes viscous and stasis occurs
What causes the vasodilation of arterioles in acute inflammation?
-Mast cells, basophils and platelets release prostaglandins, histamine and serotonin which cause vasodilation
What causes rubor/calor in acute inflammation?
-Vasodilation -> increased heat loss and increased bloodflow
Why is vasodilation beneficial in acute inflammation?
-Increased delivery of cells and chemical mediators
Why does oedema occur in acute inflammation?
-Arterial dilation -> increased HP
-Increased vascular permeability -> decreased oncotic pressure
-Increased net outflow of fluid = oedema
What two types of fluid cause oedema?
How does transudate differ from exudate?
-Transudate has a low protein content
-Exudate is protein rich
When does transudate commonly form?
-When there is increased hydrostatic pressure as in heart failure
When does exudate commonly form?
What type of exudate is commonly found with cancer?
How can oedema be used as a diagnostic tool?
-The type of fluid within the oedema can provide information about the pathological cause
How is oedema resolved?
-Increased lymphatic drainage
What are the possible mechanisms of vascular leakage?
-Increased channels and transcytosis
What chemical mediators influence endothelial contraction?
Why is the formation of fluid exudate beneficial in acute inflammation?
-Delivers nutrients, O2, cells and proteins such as Ab/fibrinogen to site of damage
-Increases lymphatic drainage
WHy is increased lymphatic drainage helpful in acute information?
-Stimulates an immune response by delivering microorganisms to the lymph nodes
Describe the process of neutrophil emigration into tissues
1)Vasodilation (vascular stasis occurs)
2)Gaps form in the endothelium (endothelial contraction)
3)Exudation (vessels become leaky)
4)Margination (stasis causes neutrophils to line up along edges)
7)Emigration through basement membrane
Why is neutrophil emigration quite a destructive process?
-Enzymes are used to break down the basement membrane of vessels
-Neutrophils cause relaxation of inter-endothelial cell junctions
Name some chemical mediators involved in vasodilation
Name some chemical mediators reaponsible for increased vascular permeability
Name some chemical mediators responsible for emigration and chemotaxis?
Name some proteases which are secreted during acute inflammation
What are prostaglandins/leukotrienes metabolites of?
What is chemotaxis?
-The movement of cells along concentration gradients of chemoattractants to the source of infection
How is chemotaxis initiated?
-Ligand-receptor binding of chemoattractant to chemoreceptor on a cell causes the rearrangement of cytoskeleton to produce pseudopods to facilitate movement
What are the three stages of phagocytosis?
How do neutrophils recognise cells for phagocytosis?
-Facilitated by opsonins-> Neutrophils have many receptors for Fc and C3a to allow detection of Ab-bound or complement-bound material
How do neutrophils digest the material they phagocytose?
-They fuse the phagosome with a lysosome, producing a secondary lysosome which destroy contents by digestion with enzymes
What are the killing mechanisms of neutrophils?
What happens in O2-dependant killing in neutrophils?
-The neutrophils use superoxide/hydrogen peroxide to kill micro-organisms
What is the O2-independent killing mechanism of neutrophils?
-Uses hydrolases, bacteriocidal permeability increasing protein and lysosomes to kill micro-organisms
Which killing mechanism of neutrophils is the most efficient?
List some local complications of acute inflammation
-Damage to normal tissue (rubor/calor/tumor/dolor)
-Obstruction/blockage of tubes by swelling
-Loss of fluid
-Pain and loss of function
-Exudate can compress vita structures (cadriac tamponade)
-Exudate can lead to the spread of infection eg perotinitis
List some systemic complications of acute inflammation
-Acute phase response
-Changes in acute phase protein conc
How does fever occur in acute inflammation?
-Endogenous pyrogens are produced (substances that induce fever)
-IL-1, TNF-a and prostaglandins reset the body's thermastat in the anterior hypothalamus to increase temperature
How does leukocytosis occur in acute inflammation?
-IL-1 and TNF-a cause accelerated release of leukocytes from the marrow
-Macrophages and lymphocytes produce CSF which further stimulates the marrow
Which leukocyte is mainly associated with bacterial infection?
Which leukocyte is mainly associated with viral infection?
What is the acute phase response?
-Increased Heart rate
-Altered sleeping patterns
What acute phase proteins can become altered in acute inflammation?
What is shock?
-Circulatory failure caused by decreased blood volume due to systemic vasodilation and oedema
What are the 4 possible resolutions from acute inflammation?
-Continued acute inflammation with chronic inflammation = abscess
-Chronic inflammation and fibrous repair
What happens in complete resolution of acute inflammation?
-Morphological changes reverse
-Vascular changes stop
-Exudate drains to lymphatics
-Neutrophils die and are phagocytosed
-Regeneration of tissue
When can regeneration of cells not occur?
-When the architecture of the cell has been destroyed
How are mediators of acute inflammation removed?
-Mediators have short half lives
-Enzymes and proteins are inactivated by degredation eg fibrin by plasmin
-Some mediators are unstable
-Inhibitors can bind to mediators
-Specific inhibitors of the acute inflammatory response
-Dilution by exudate
What is the causative organism of lumbar pneumonia?
What are the symptoms of lobar pneumonia?
-Hypoxaemia over a few days as exudate fills alveoli
What are the predominant features in a skin blister?
How does exudate result in a blister?
-The collection of fluid strips off the overlying epithelia
What are the possible outcomes of a skin blister?
Why is the exudate clear in a skin blister?
-Contains relatively few inflammatory cells
In what type of tissues do abscesses occur?
How does exudate result in an abscess?
-Inflammatory exudate forces the tissue apart and liquefactive necrosis occurs in the centre
Why is an abscess painful?
-From the high amount of pressure
How can abscesses cause damage to other tissues?
-Can squash adjacent tissues
How does acute inflammation occur in serous cavities?
-Through leakage of exudate
What is an ascites?
-A collection of fluid in the peritoneum causing swelling
What is often the cause of acute appendicitis?
-Blockage of the lumen by faecolif, tumour or viral infection (swelling of closely associated lymph nodes)
How does the blockage of the appendix lead to appendicitis?
-Blockage causes stasis of appendiceal contents
-Multiplication of bacteria
-Tissue inflammation, necrosis, ulceration and exudate formation
-Swelling due to vasodilation and exudate formation = oedema
What is ulceration?
-Depression in epithelial surface due to loss of epithelia
What are the possible outcomes of perforation of the appendix?
-Liver abscess via septicaemia -> hepatic portal vein
What is the common cause of bacterial meningitis in neonates?
What is the common cause of bacterial meningitis in children?
-Haemophilus Influenzae B
What is the most common cause of bacterial meningitis in young adults?
What is the most common cause of bacterial meningitis in the elderly?
What causes the neurological symptoms in bacterial meningitis?
-Purulent pus/exudate rich with neutrophils appears on the brain causing swelling and increasing intracranial pressure leading to neurological symptoms
What neurological symptoms are commonly seen in bacterial meningitis?
-Hearing and vision loss
-Coordination and balance problems
-Poor memory and concentration
How can bacterial meningitis lead to gangrenous limbs?
What is waterhouse-friderchsen syndrome? What is it a sign of?
-Adrenal gland failure caused by bleeding and haemorrhage into the adrenal glands
What is ascending cholangitis?
-A bile duct infection which is retreating up the bile duct
What is the main cause of ascending cholangitis?
-Gallstone impaction causes blockage of the common bile duct
-Replication of bacteria causes acute inflammation of the bile duct which can back up into the liver
How can ascending cholangitis cause a liver abscess?
-Inflammation of the liver occurs due to it ascending up the common bile duct
-Liquefactive necrosis of the liver and inflammation leads to an abscess forming
-What is the common bacteria to cause ascending cholangitis?
Why does ascending cholangitis have leukocytosis?
-Many macrophages due to bacterial infection
-Macrophages secrete CSF which stimulates the BM
Why is there a raised ALT, bilirubin and alkaline phosphatase when there is a liver abscess?
-Leaky cells due to inflammation and destruction of hepatocytes
What are possible complications of ascending cholangitis?
What is gallstone ileus?
-gallstone erodes through gall bladder into duodenum, possibly obstructing the terminal ileum (can lead to rupture as no faeces can pass)
Why can gallstones lead to acute pancreatitis?
-Gallstone blocks the common bile duct distal to the pancreas resulting in pancreatitis
What is hereditary angio-oedema?
-Rare autosomal dominant disorder of acute inflammation where there is deficiency of C1-esterase inhibitor leading to angio-oedema
Why does c1-esterase deficiency cause angio-oedema?
-C1-esterase inhibits bradykinin.
-Deficiency of this enzyme means bradykinin is uninhibited
-Uninhibited bradykinin leads to increased vascular permeability and thus angio-oedema
How is hereditary angio-oedema characterised?
-Rapid attacks of non-itchy cutaneous angio-oedema including the dermis, subcutaneous tissue, mucosa and submucosa
-Possible recurrent abdo-pain due to intesinal oedema
How is hereditary angio-oedema treated?
What is a1-antitrypsin deficiency?
-Autosomal recessive disorder of acute inflammation with vary severity caused by deficiency/no a1-antitrypsin
What is a1-antitrypsin?
-Protease inhibitor which deactivates enzymes released from neutrophils at the site of inflammation
How does a1-antitrypsin deficiency result in emphysema?
-Elastase is not inhibited which results in destruction of the parenchyma of the lung
Why does a1-antitrypsin deficiency cause liver sclerosis?
-Misfolding of the protein results in accumulation in the ER as it cannot be exported
-Hepatocyte damage leading to sclerosis and cirrhosis
What is chronic granulomatous disease?
-A recessive sex-linked disorder of acute inflammation where immune phagocytes cannot generate superoxide radicals
Why is not producing superoxide radicals in chronic granulomatous disease a problem?
-Immune phagocytes cannot destroy ingested bacteria resulting in the formation of granulomas and abscesses in the skin, lymph nodes, lung and liver in order to contain the bacteria