Acute Inflammation Flashcards
What are the features of acute inflammation?
- innate
- immediate
- stereotyped (same response every time/every case)
- short (min/hrs)
Define inflammation.
Response of living tissue to injury, initiated to limit tissue damage
What are some of the causes of acute inflammation?
- microbial infections e.g. pyogenic organisms
- hypersensitivity reactions
- physical agents e.g. trauma
- chemicals
- tissue necrosis
What are the clinical signs of inflammation?
Local: RUBOR (redness) TUMOR (swelling) CALOR (heat) DOLOR (pain/loss of function)
+ exudate of oedema & infiltrate of cells
Systemic:
Fever
Tachycardia
Describe the sequence of events in the vascular phase of acute inflammation.
- Transient vasoconstriction of arterioles (secs)
- Vasodilatation of arterioles -> vasodilatation of capillaries (increased blood flow -> rubor & calor) (+histamine)
- Increased permeability of blood vessels -> exudation of protein-rich fluid into tissues (+histamine)
- Increased RBCs in small vessels and increased viscosity of blood (stasis) -> slowed circulation
note: histamine also causes pain to enforce rest (preventing further damage)
Describe the sequence of events in the exudation phase of acute inflammation.
Arteriolar dilatation -> increased hydrostatic pressure
& increased permeability -> loss of protein into interstitium
= flow of fluid out of vessel -> OEDEMA
Delivers plasma proteins to site of injury (IGs, inflamamtory mediators, fibrinogen)
Dilutes toxins
Increases lymphatic drainage (delivers microbes to phagocytes and antigens to immune system)
What causes the increased permeability of blood vessels during the exudation phase of acute inflammation?
- endothelial contraction creates gaps (+histamine & leukotrienes)
- cytoskeletal reorganisation creating gaps (IL-1 & TNF)
- direct injury e.g. toxins, burns, chemicals
- leukocyte-dependent injury due to toxic oxygen species & enzymes released
- increased transcytosis (channels across endothelial cytoplasm) (VEGF)
What is the difference between exudate and transudate?
EXUDATE = fluid loss in inflammation with a high protein content
TRANSUDATE = fluid loss due to increased hydrostatic pressure with a low protein content
e.g. cardiac failure, venous outflow obstruction
Describe the sequence of events in the cellular phase of acute inflammation.
Infiltration of neutrophils (polymorphs) removes pathogens and necrotic debris. Attracted by bacterial products.
- Margination: Stasis causes neutrophils to line up at edge of blood vessels along endothelium
- Rolling: neutrophils stick to receptors on endothelium intermittently, causing them to “roll” along the endothelium
- Adhesion: neutrophils fully adhere to endothelium
- Emigration: neutrophils move through endothelium (diapedesis) by chemotaxis
- Extravasation: neutrophils now outside blood vessels
List some chemical mediators of acute inflammation.
Proteases e.g. kinins, complement system (C3a & C5a), coagulation/fibrinolytic system
Prostaglandins/leukotrienes (arachidonic acid metabolites)
Cytokines/chemokines e.g. interleukins, TNF-alpha
note: increased blood flow (histamine & prostaglandins)
increased vascular permeability (histamine & leukotrienes)
neutrophil chemotaxis (C5a, LTB4, bacterial peptides)
phagocytosis (C3b)
What are some local complications of acute inflammation?
- swelling -> blockage of tubes e.g. bile duct, intestine
- exudate -> compression of soft organs where there is little space e.g. cardiac tamponade
- > serositis: infection of serous cavity due to exudate on surface of organ (e.g. ascites, pleural effusion, pericardial effusion) -> localised fibrin deposits, respiratory/cardiac impairment
- > loss of fluid e.g. burns
- pain & loss of function (dolor)
What are some systemic effects of acute inflammation?
- fever: endogenous pyrogens produced (e.g. IL-1, TNF-alpha) & prostaglandins
- leukocytosis:
= IL-1 & TNF-alpha accelerate release of leukocytes from bone marrow
= macrophages & T-lymphocytes produce colony-stimulating factors
note: bacterial infections = neutrophils (Acute)
viral infections = lymphocytes (Chronic)
- acute phase response: reduced appetite (anorexia), increased heart rate, altered sleep patterns
What is the definition of shock, and what can it be caused by?
SHOCK = circulatory collapse when the arterial blood pressure is too low to adequately perfuse tissues
- hypovolaemic: reduced circulatory volume
- cardiogenic: reduced activity of heart
- septic: widespread dilatation of blood vessels due to sepsis
What are some of the possible results of acute inflammation?
- complete resolution: vascular changes stop, exudate drains to lymphatics, fibrin degraded by plasmin/proteases, neutrophils die and are carried away/phagocytosed, damaged tissue may regenerate
note: not possible if tissue architecture has been destroyed - continued acute inflammation with chronic inflammation -> abscess
- progresses to chronic inflammation -> fibrous repair and tissue regeneration
- septic shock
What is the definition of an abscess? How can you treat it?
Localised collection of pus and necrotic tissue in solid tissue surrounded by damaged, inflamed tissue e.g. boil
note: inflammatory exudate forces tissue apart -> extreme pain due to increased pressure (therefore invariably some tissue destruction around an abscess)
Incise and drain to relieve pressure
How are mediators of inflammation inactivated?
- short half lives
- degraded e.g. heparinases
- inhibited e.g. anti-proteases
- unstable e.g. arachidonic acid derivatives
- diluted in exudate e.g. fibrin exudation products
- specific inhibitors e.g. endothelin, lipoxins
Describe appendicitis. What are the causes? What are the complications?
Inflammation due to obstruction of appendiceal lumen
Causes:
- inflammatory bowel disease causing lymphoid hyperplasia
- infection
- faecal stasis & faecaliths (hard mass of faeces within colon/appendix due to chronic constipation)
- foreign bodies
- neoplasms
Increased WBCs due to increased intestinal bacteria (obstruction)/stagnated mucus (increased mucus secretion)
-> pus formation -> further increase in pressure -> venous outflow obstruction ——->
-> ischaemia -> loss of epithelial integrity -> invasion of bacteria
OR: -> thrombosis of appendicular blood vessels -> perforation (disrupted continuity causing leakage of contents) -> gangrene -> peritonitis/periappendicular abscess (faeces entering peritoneal cavity)
What is the definition of an ulcer?
ULCER = permanent loss of epithelium on a mucosal surface
What is the difference between sepsis, septic shock, and septicaemia?
SEPSIS = putrefactive destruction of tissues by disease-causing bacteria and their toxins
SEPTIC SHOCK = widespread dilation of blood vessels so that there is insufficient blood to fill them due to severe sepsis, with resultant systemic inflammatory response associated with disseminated intravascular coagulation and multiple organ failure
SEPTICAEMIA = widespread destruction of tissues due to absorption of disease-causing bacteria or their toxins into the bloodstream (“blood-poisoning”)
What are some long-term complications of meningitis?
- septicaemia -> gangrene
- cognitive impairment
- hearing problems
- seizures/epilepsy
- neuromotor disability
- visual disorders
What is the link between gallstones and hepatic abscesses?
Obstructed bile duct -> infection of bile duct (ascending cholangitis)
Describe the sequence of events following the inhalation of Streptococcus pneumoniae.
Bronchopneumonia (bronchi -> alveoli):
Alveoli filled with exudate -> consolidation in alveoli only -> fibrosis of lung tissue -> RESOLUTION
Lobar pneumonia (alvoli -> alveoli): Alveoli filled with exudate - consolidation in whole lobule -> fibrosis of lung tissue -> RESOLUTION
What is inherited angio-oedema?
Absence of C1-esterase inhibitor -> increased bradykinin (formed from kiniogen) which increases vascular permeability
Increased capillary leakage -> widespread oedema
Laryngeal oedema -> asphyxiation
What is chronic granulomatous disease?
Reduced NADPH oxidase
Ineffective phagocytosis (no oxidative burst) and unregulated neutrophil activity -> vulnerable to infection -> recurrent infections & areas of granuloma e.g. bones, bowel
