Acute Inflammation Flashcards
What is inflammation?
A complex reaction of vascularised connective tissue to local injury
What are the purposes of inflammation? (3)
1) Contain/isolate injurious stimulus
2) Destroy/dilute/wall off agents to neutralise toxins
1 + 2 = LIMIT DAMAGE
3) Repair damage caused
What is inflammation classified according to?
Time course
What are the two types of inflammation?
- Chronic
- Acute
What is acute inflammation?
Inflammation of relatively short duration. Quick response
What is chronic inflammation?
Inflammation of relatively long duration
What does acute inflammation response time depend on? (2)
- Pathogen causing injury
- Body ability to respond to injury
What are the two parts that make up the name given to an infection?
- Name of organ/tissue
- Suffix “itis”
What are the 5 signs of acute inflammation?
- Heat
- Redness
- Swelling
- Pain
- Loss of function
What is heat and redness caused by in acute inflammation?
Hyperaemia (increased blood flow)
What is swelling caused by in acute inflammation?
Increased amount of fluid in tissue (exudate)
What 2 things is pain caused by in acute inflammation?
- Neural damage
- Chemical mediators e.g across gland
Why is pain important in acute inflammation?
For awareness of event
What can loss of function be caused by in acute inflammation?
Pain
-
What does loss of function be caused in acute inflammation depend on?
Specific part affected by inflammation e.g reduced mobility in joint
What are the 3 processes an injury triggers in acute inflammation?
- Vascular changes
- Cellular events
- Chemical mediators
What is the first immediate vascular reaction in acute inflammation?
Rapid transient vasoconstriction of arterioles to reduce blood flow
Why is there an initial rapid transient vasoconstriction of arterioles to limit blood flow in acute inflammation?
Limit pathogenic spread
What is the change in vascular calibre after the initial transient vasoconstriction in acute inflammation?
Vasodilation to increase blood flow to capillaries
What activates the vasodilation after initial transient vasoconstriction in acute inflammation?
Chemical mediators activated
Causes damaged tissues releasing INF and interleukins
- Nitric oxide released
- Dilates vessels
What activates the vasodilation after initial transient vasoconstriction in acute inflammation? (4)
- Chemical mediators activated
- Causes damaged tissues releasing INF and interleukins
- Nitric oxide released
- Dilates vessels
Why is there vasodilation after initial transient vasoconstriction in acute inflammation? (2)
- Dilute pathogenic agent
- Increases WBCS locally
What changes occur in vascular calibre during acute inflammation?
Rapid transient vasoconstriction of arterioles followed by vasodilation
What changes occur in blood flow during acute inflammation?
Initial reduction of blood flow followed by increased blood flow to capillaries
What changes occur in vascular permeability during acute inflammation?
Increased permeability of microvasculature
What is the purpose of increased permeability of microvasculature during acute inflammation? (4)
- Blood vessels leak fluid and protein
- Losing protein reduces oncotic pressure in vessels
- Favours fluid movement to interstitium
- Allows migration of WBCs from vessel to interstitium
What is exudate? (3)
- Protein rich fluid from plasma (similar protein levels)
- Inflammatory
- Extravascular
What is tissue swelling/oedema caused by in acute inflammation? (3)
- Increased hydrostatic pressure
- Decreased osmotic gradient
- Increased fluid in interstitium
Is swelling always a sign of inflammation?
No
What is the colour of exudate the same colour as?
Plasma
What is inflammatory swelling caused by?
Oedema due to accumulation of exudate
What is the specific gravity of exudate?
More than 1.020
What is non inflammatory swelling caused by?
Oedema due to accumulation of transudate
What is transudate? (3)
- Ultrafiltrate of blood
- Low protein
- No inflammatory cells
What is the specific gravity of transudate?
Less than 1.012
What is transudate swelling often found in and why?
Pregnancy due to increased BP
List the cellular events that occur in acute inflammation (3)
- Leucocyte transmigration
- Leucocyte degranulation
- Phagocytosis
Why is leucocyte transmigration necessary in acute inflammation?
Leucocytes need to move from circulation to damage site
What are the two steps to leucocyte transmigration and degranulation in acute inflammation?
- Extravasation
- Migration
What occurs in extravasation during leucocyte transmigration and degranulation in acute inflammation?
Endothelial cells and leuocytes express mutually recognising adhesion molecules
How do leucocytes migrate during leucocyte transmigration and degranulation in acute inflammation? (2)
Leuocytes “roll” from one adhesion molecule to another on endothelium
- Until eventually reach molecule enabling transmembrane WBC movement
What allows leucocytes to “roll” loosely during leucocyte transmigration and degranulation in acute inflammation?
Bonds to adhesion molecules are not very strong
What ensures leucocytes migrate towards the wound site in leucocyte transmigration and degranulation in acute inflammation? (2)
- More adhesion proteins closer to wound site
- Follow conc. gradients of chemicals and inflammatory mediators (chemotaxis)
Define chemotaxis
Movement of a cell in direction due to gradient of increasing or decreasing concentration of a particular substance
What is phagocytosis?
Phagocytes binding to material to ingest in multistep process
Give 2 examples of material ingested in phagocytosis
- Bacteria
- Necrotic tissue
What are the steps of phagocytosis? (3)
- Recognition and attachment
- Engulfment
- Killing/degradation
How does recognition and attachment occur in phagocytosis? (2)
- Through own cell receptor
- Molecules released by other cells bound to agent to eliminate
How does engulfment occur in phagocytosis?
Pseudopodia surrounds agent producing a vacuole
What is the vacuole produced in phagocytosis engulfment called?
Phagosome
How does killing/degradation occur in phagocytosis? (2)
- Lysosomal granules fuse with phagosome
- Activates destruction by releasing chemicals
What chemicals are released to activate killing/degradation in phagocytosis?
- Lysozymes
- Proteases
- Hydrolase (oxygen independent)
- Toxic superoxides (oxygen dependant)
What are the two types of chemical mediators released in acute inflammation?
- Plasma mediators
- Cell mediators
What occurs when leucocytes reach the inflammation site after transmigration?
Release cytokines (degranulation)
What are plasma mediators?
Present in precursor form and need to be activated
What are the 3 types of plasma mediator?
- Cogulation system
- Kinin system
- Complement system
What are cell mediators?
- Normally sequestered in intracellular granules (released from cells in inflammatory process)
- Synthesised de novo
What is the life length of chemical mediators once released from cells and why?
Short lived because inflammatory process should be self contained
What are the 3 types of cell mediators?
- Mast cells
- Basophils
- Platelets
What is the coagulation system activated by?
Tissue damage
What is the end product of the coagulation system?
Fibrin
What is the purpose of fibrin in the coagulation system? (2)
- Mesh limiting site of infection in coagulation cascade
- Provides clot to stop bleeding
What is the purpose of thrombin in the coagulation system? (2)
- Increases leukocyte adhesion
- Increases fibroblast proliferation
What reaction does thrombin catalyse?
Degradation of fibrinogen into fibrin
What is the purpose of factor Xa in the coagulation system? (3)
- Increases vascular permeability
- Increases leukocyte exudation
- Modulates ability of WBCs to migrate externally
What is fibrin degraded to?
Fibrinopeptide
What is the purpose of fibrinopeptide? (2)
- Acts as a chemotactic factor for leucocytes
- Increases endothelial permeability
What is a chemotatic factor?
Acts as a chemical stimulus along a concentration gradient, attracting cells to a site of inflammation
What overall effect does fibrinopeptide/degradation of fibrin have? (2)
- More cells to damaged site
- More blood flow to damaged site
What is the kinin system activated through?
Coagulation factor XII
What is the end product of the kinin system?
Bradykinin
What does kinin system cause? (2)
- Vasodilation
- Triggers pain
What is the purpose of the complement system?
- Triggers expression of adhesion molecules on leucocytes
- Components accumulate on surface of pathogenic agent to promote recognition = phagocytosis
- Triggers other cells = intercellular mediator release e.g histamine
How many components are there in the complement system?
20
What is the complement system activated by?
Foreign substances
What are the 3 parts of the complement system?
- Opsonisation
- Binding
- Phagocytosis
What is opsonisation?
Invading particle e.g bacteria is identified to the phagocyte
List the chemical mediators involved in lysis of microbes (6)
- Membrane attack complex (MAC)
- C5
- C6
- C7
- C8
- C9
What chemical mediator acts as an opsonin?
C3b
What chemical mediator is a powerful chemotactic agent?
C5a
What chemical mediators increase permeability and cause vasodilation through histamine? (3)
- C3a
- C5a
- Anaphylatoxins
What hormone causes vasodilation with the aid of chemical mediators?
Histamine
What is histamine produced by? (3)
- Mast cells
- Basophils
- Platelets
What is histamine released in response to? (4)
- Physical injury
- Trauma
- Cold/heat
- Immune reaction
What does histamine increase? (3)
- Arteriole dilation
- Venule vascular permeability
- Activation of inflammatory cascade
What are the vasoactive amine chemical mediators of inflammation? (2)
- Histamine
- Serotonin
What is serotonin produced by in inflammation? (2)
- Platelets
- Enterochromaffin cells
What are the actions of serotonin similar to?
Histamine
List the chemical cell mediators of inflammation (7)
- Arachidonic acid metabolites
- Cytokines and chemokines
- Nitric oxide
- Platelet activating factor
- Lysosomal constituents of leukocytes
- Oxygen derived free radicals
- Neuropeptides
What are arachidonic acid metabolites also known as?
Prostaglandins
What is the purpose of arachidonic acid metabolites? (2)
- Arterior dilatation
- Pain
What is the purpose of cytokines and chemokines? (2)
- Increase vascular permeability
- Chemotaxis
What are cytokines and chemokines released by?
Blood cells
What does nitric oxide cause?
Vasodilation
What is the purpose of platelet activating factor? ()
- Platelet aggregation
- Increased vascular permeability
- Leucoyte activation (+adhesion molecules)
- Chemotaxis
What is the purpose of lysosomal constituents of leukocytes?
Phagocytosis
What is the purpose of neuropeptides?
Pain
List the systemic effects of acute inflammation (7)
- Fever
- Malaise/lethargy/sleppiness
- Pain
- Leucocytosis
- Tissue damage
- Hyperpyrexia
- Shock/Death
What 3 chemical mediators released by damaged tissue cause fever in acute inflammation?
- IL1
- IL6
- TNF
How do Il1, IL6 and TNF cause fever in acute inflammation?
Release prostaglandins resetting hypothalmic thermostat to increase set point temp
What is the purpose of fever in acute inflammation?
Destroys bacteria/virus
Why can acute inflammation fever be damaging?
Can increase risk of seizures
What drugs are needed to bring down fever in acute inflammation?
Non-steroidal anti-inflammatory drugs (NSAIDs)
What is malaise caused by in acute inflammation?
Cytokines affecting brain to reduce counterproductive behaviour
What 2 chemical mediators cause pain in acute inflammation?
- Prostaglandins
- Bradykinin
Other than chemical mediators, what causes pain in acute inflammation?
Localised nerve damage
What is one of the first signs of acute inflammation?
Leucocytosis
What is leucocytosis? (2)
- Colony stimulating factors stimulate release of leucocytes from bone marrow
- Big increase in WBC in blood systemically
What 3 chemicals released in acute inflammation cause tissue damage?
- Neutrophil and macrophage lysosomal enzymes
- Oxygen metabolites
- Nitric oxide
Why is there often brain damage in acute inflammation?
Swelling in a confined space
What causes hyperpyrexia/shock/death in acute inflammation?
Too many cytokines
What is hyperpyrexia?
Extreme elevation in body temp (+40c)
What are the 4 types of acute inflammation?
- Serous inflammation
- Fibrinous inflammation
- Suppurative inflammation
- Ulcer
What does the type of inflammatory response depend on?
The organ
What is serous inflammation?
Exudation of transudate into space caused by
- Tissue damage (skin blister)
- Body cavities (effusion)
What are the causes of serous inflammation? (3)
- Increased BP
- Reduced oncotic pressure
- Mechanical trauma
What is exudation?
Fluid being emitted by organism through wound/pores
What is fibrinous inflammation?
Fibrinogen exits blood and accumulates as fibrin in extracellular space
What are the 2 causes of fibrinous inflammation?
- Increased vascular permeability
- Procoagulant stimuli (tumours)
What occurs if fibrinolysis is not complete?
Scarring
What is purulent inflammation?
Production of pus
What does pus in purulent inflammation contain? (4)
- Neutrophils (dead/alive)
- Cellular debris
- Oedema
- Sometimes microorganisms
What common infection involves purulent inflammation?
Appendicitus
How does appendicitus progress to peritonitus?
If purulent exodate reaches the serosa
What is purulent exodate a type of?
Inflammatory infiltrate
Label the histology picture of appendicitus
See notes for diagram
What is pus a type of?
Inflammatory exudate
What is abscess?
Localised collection of pus surrounded by fibrous tissue, confined so can’t be drained
What is the advantage of abscess?
Normally physiologically protective - contains infection
What is the disadvantage of abscess?
Doesn’t allow antibiotics to permeate
How is abscess treated?
Surgery for drainage and debriment
What is debriment?
Removal of damaged tissue/foreign objects from a wound
What is empyema?
Pus (exudate) formation in existing body cavity
Give 4 examples of body cavities that empyema could occur in
- Pleura
- Joints
- Uterus
- Pericardium
Where is pus often found in the skin?
Acne - localised accumulation of pus in the skin
When is pus found in the gall bladder?
Cholecystitis (esp. after gall stones)
What does the outcome of acute inflammation depend on?
- Type of injury
- Ability of body to respond
What are the 4 non death outcomes of acute inflammation?
- Complete resolution
- Healing by fibrosis
- Abscess formation
- Chronic inflammation
What is the advantage of healing by fibrosis?
Puts connective tissue patch on damage, resists further damage
What is the disadvantage of healing by fibrosis?
Area no longer functioning
In what 2 ways can acute inflammation cause death?
- Severe local damage
- Uncontrolled infection
Give 2 conditions where severe local damage caused by acute inflammation leads to death
- Meningitus
- Endocarditus
How does uncontrolled infection in acute inflammation lead to death?
- Sepsis
- Shock