ICS Flashcards
2 good scenarios of inflammation, 2 bad scenarios of inflammation
good: infection and injury
bad: autoimmunity (where body starts to attack its own cells and tissues), hypersensitivity
differences between acute and chronic inflammation
Acute:
–Sudden onset
– Short duration
– Usually resolves
Chronic:
– Slow onset or sequel to acute
– Long duration
– May never resolve
5 types of cells involved in inflammation
- Neutrophil polymorphs
- Macrophages
- Lymphocytes
- Endothelial cells
- Fibroblasts
Neutrophil polymorphs
1- lifespan
2- sequence in acute inflammation
3- roles in inflammation
1: short lived (hours)
2: usually first on scene of acute inflammation
3: roles:
- cytoplasmic granules full of enzymes that kill bacteria
- usually die at the scene of inflammation
- release chemicals that attract other inflammatory cells such as macrophages
macrophages
1- lifespan
2- roles in inflammation (4)
1- long lived (weeks to months)
2- phagocytic properties, ingest bacteria/debris may carry debris away, may present antigen to lymphocytes
lymphocytes
1- lifespan
2- roles in inflammation
1- long lived (years)
2- produce chemicals which attract in other inflammatory cells, immunological memory for past infections and antigens
Endothelial cells
1- location
2- 3 roles in inflammation
1- line capillary blood vessels in areas of inflammation
2-
(1) become sticky in areas of inflammation so inflammatory cells adhere to them
(2) become porous to allow inflammatory cells to pass into tissues
(3) grow into areas of damage to form new capillary vessels
Fibroblasts
1- lifespan
2- role in inflammation
1- long lived cells
2- form collagen in areas of chronic inflammation and repair
Acute inflammation example
- cell
- blood vessels
- inflammation of… and effect
- outcomes
Acute appendicitis:
- unknown precipitating factor
- neutrophils appear
- blood vessels dilate
- inflammation of serosal surface occurs, pain felt
- appendix either surgically removed or inflammation resolves or appendix bursts with generalised peritonitis and possible death
Chronic inflammation example
- what doesn’t occur?
- cells involved
- what then occurs?
Tuberculosis
- no initial acute inflammation
- myobacteria ingested by macrophages, which often fail to kill the myobacteria
- lymphoccytes and macrophages appear
- fibrosis occurs
what is a granuloma?
mass of granulation tissue which is usually produced in response to infection/inflammation/ presence of a foreign substance. epithelioid histiocytes
3 steps of acute inflammation
Potential outcomes of acute inflammation
(1) vascular component- dilation of vessels
(2) Fluid Exudative component- vascular leakage of protein-rich fluid due to increased vascular permeability
(3) Cellular exudative component- Neutrophil polymorph is the characteristic cell recruited to the tissue
Outcomes possible; resolution, suppuration (e.g. abcess), organisation or progression to chronic inflammation
6 main causes of acute inflammation
(1) Microbial infections- e.g. pyogenic bacteria, viruses, fungal etc. Bacteria release exotoxins (chemicals synthesised by them that specifically initiate inflammation) or endotoxins (associated with their cell walls). Some microorganisms cause immunologically mediated hypersensitivity reactions e.g. parasitic infections and tuberculosis
(2) Hypersensitivity: inappropriate/excessive immune reaction which damages tissues
(3) Physical agents e.g. trauma, ionising radiation, heat, cold
(4) Chemicals
(5) Bacterial toxins
(6) Tissue necrosis- death of tissues from lack of oxygen/nutrients resulting from inadequate blood flow (infarction) or a potent inflammatory stimulus. Often shows acute inflammatory response (resumably in response to peptides released from the dead tissue)
5 macroscopic appearances of acute inflammation
(1) Rubor (redness)- due to dilation of blood vessels in damaged area
(2) Calor (heat)- temp increase due to hyperaemia and resultant vascular dilation (and also systemic favour)
(3) Tumor (swelling)- result from oedema and physical mass of inflammatory cells migrating into area; progression of inflammation response leads to formation of new connective tissue contributes to the swelling
(4) Dolor (pain)- stretching and distortion of tissues due to inflammatory oedema and pus under pressure in abcess cavity. Also some chemical mediators of inflammation (bradykinin/prostaglandin/serotonin- involved in acute) are known to induce pain
(5) Loss of function
chemical mediators of acute inflammation- effects
(1) injured tissue releases chemical substances following injury into uninjured areas- leads to spread of acute inflammatory response
(2) early in immune response, histamine and thrombin released by original inflammatory stimulus cause up-regulation of adhesion molecules on the surface of endothelial cells. Overall effect of molecules is the firm neutrophil adhesion to the endothelial surface
(3) endogenous chemical mediators cause vasodilation, emigration of neutrophils, chemotaxis, increased vascular permeability, itching and pain
Plasma enzymatic cascade systems
(1) complement
(2) kinin
(3) Coagulation
(4) Fibrinolytic
what is the best known chemical mediator in acute inflammation?
Histamine
list 3 medications for inflammation
- Aspirin
- Ibuprofen
- Paracetamol
what do macrophages do?
ingest bacteria n debris
may carry debris away
may present antigen of lymphocytes
what do lymphocytes do?
produce chemicals which attract other inflammatory cells
have an immunological memory for past infections and antigens
where are inflammatory cells?
in bone marrow, released into blood
outcomes of acute inflammation
(1) Resolution
(2) Suppuration- if there is excessive exudate, leads to pus production
(3) organisation (due to exessive necrosis or suppuration)
(4) Progression to chronic inflammation
Systemic effects of inflammation
- pyrexia
- constitutional symptoms
- weight loss
- reactive hyperplasia of the reticuloendothelial system (the enlargement of an organ or tissue caused by an increase in the reproduction rate of its cells,)
- heamatological changes
- amyloidosis (abnormal protein produced in bone marrow builds up in organs and can be deposited in any tissue or organ)
causes of chronic inflammation (4)
(1) primary chronic inflammation
(2) transplant rejection
(3) Progression from acute inflammation
(4) recurrent episodes of acute inflammation
macroscopic appearances of chronic inflammation
(1) chronic ulcer
(2) chronic abscess cavity
(3) thickening of the wall of a hollow viscus
(4) granulomatous inflammation
(5) fibrosis
1- what is healing?
2- what regulates healing and repair?
1- healing involves regeneration and migration of specialised cells. Repair consists of angiogenesis (formation of blood vessels), fibroblast proliferation and collagen synthesis resulting in granulation tissue
2- growth factors which bind to specific receptors on cell membranes and trigger a series of events culminating in cell proliferation
two types of lymphocytes
1- B lymphocytes- on contact with antigen become progressively transformed into plasma cells, which are cells specially adapted for the production of antibodies
T Lymphocytes- responsible for cell-mediated immunity. On contact with antigen, T lymphocytes produce a range of soluble factors called cytokines, with important activities such as recruitment and activation of other cell types
what is resolution? (2)
(1) initiating factor removed
(2) tissue undamaged or able to regenerate
what can a paracetamol OD result in?
liver failure
how does alcoholism impact regeneration in liver?
bc of ongoing damage which results in abnormal architecture (cirrhosis)
which cells lining the alveoli can regenerate?
pneumocytes
what are the most superficial skin wounds & an example?
What happens during this type of injury?
abrasion eg road rash from cycling
only top cell layer is removed, leaving the bottom layer/follicles/glands for scab to form and for the epidermis to eventually be regenerated
what are the 2 types of skin would healing?
Describe them?
1st and 2nd intention healing
1st intention:
- edge to edge healing (heals w/ reasonable scar)
both ends are sealed together
- the slight gap is filled w blood, fibrin etc which holds together a little w stitches
- epidermis regrows, fibroblasts produce collagen
- scar line is stronger than surrounding tissue as more blood vessels are grown
2nd intention= traumatic wound where u can’t bring 2 edges together
granulation –> epithelium slowly grows in from edges (depending on wound size)
define repair
replacement of damaged tissue by fibrous tissue
what is collagen prod by?
fibroblasts
after a MI, what is there where dead heart tissue was?
a fibrous scar
what type of scar does MF (myocardial fibrosis) result in?
a dense white fibrous scar (patient may live for a few months but may die after)
if healing by 2nd intention, we don’t want infection… what may be done to reduce this?
artificial skin dressings to keep the skin moist so it doesn’t dry out - sometimes may have growth factors in them
what is fibrosis in the brain called?
Gliosis
how does stroke recovery happen?
only the injured (not dead tissue) around the edge of the infarct gets better, with plasticity involved
list some cells that regenerate (5)
- hepatocytes
- pneumocytes
- all blood cells
- gut and skin epithelium
- osteocytes
what are some cells that don’t regenerate? (2)
- Myocardial cells
2. Neurones
Why are clots rare in normal blood flow? (2)
- Laminar flow (endothelial cells travel in the centre of arterial vessels and don’t usually touch the sides)
- Endothelial cells are not sticky when healthy.
Define thrombosis
the formation of a solid mass from BLOOD CONSTITUENTS in an intact vessel of a living person.
3 steps of thrombosis
- Platelet aggregation (due to exposed collagen)
- Chemicals released during aggregation lead to further aggregation and also begin the clotting cascade of proteins in the blood (POSITIVE FEEDBACK LOOPS)
- Clotting cascade results in formation of FIBRIN (large protein molecule) which makes a mess in which red blood cells can become entrapped.
What is the thrombosis triad? (VIRCHOW’S TRIAD)
The three main factors which result in thrombosis- usually a combination of two or three
- Changes in the vessel wall
- change in blood constituents
- change in blood flow
What is an embolism? What causes it?
Embolism= process of solid mass in blood being carried through circulation to a place where it gets stuck and BLOCKS VESSEL
Usually due to thrombus but can also be due to air (due to iv/bloods), cholesterol crystals (due to atheromatous plaques), tumor, amniotic fluid. fat (severe trauma with multiple fractures)
What is ischaemia?
reduced blood flow to a tissue without other implications
What is infarction? What causes it? Why are most organs susceptible to infarction?
Reduction in blood flow to a tissue which is so severe that it cannot even support maintenance of the tissue cells, resulting in them dying.
Usually caused by thrombosis of a supplying artery.
Most organs are susceptible because most organs are only supplied by a single artery (end artery supply), so very susceptible to infarction
Which organs are less susceptible to infarction and why?
Some organs are less susceptible to infarction because they have dual artery supply so if there is thrombosis in one, they have supply from another. These include;
- liver (portal venous & hepatic artery)
- lung (pulmonary venous & bronchial)
- brain (circle of willis)
what does occlusion of a coronary artery result in?
death of heart muscle due to lack of blood flow (MI)
what does occlusion of a cerebral artery result in?
death of brain tissue due to a lack of blood flow (CI)
what is a stroke aka?
cerebral infarction (CI)
why does thrombosis in the veins most commonly occur?
due to slow blood flow within those veins eg when a patient is lying in bed for long periods of time after a major op
list some preventions of DVT (deep vein thrombosis) in hosp (3)
- early mobilisation
- use of small doses of anti-coagulants eg heparin
- venous stocking to prevent leg veins being full of blood
what is heparin?
an anti-coagulant
if an embolus enters the venous system, where will it lodge?
it will travel to the vena cava –> through RHS of heart –> &will lodge in pulmonary arteries
why can’t an embolus in the venous system get through to arterial circulation?
bc the blood vessels in the lung split down to capillary size so lung acts as a filter for any venous emboli
(aka lung acts as a FILTER for venous emboli)
what happens if an embolus enters the arterial system?
it can travel anywhere downstream of its entry point eg a mural thrombus overlying a myocardial infarct in LV can go anywhere in systemic circulation
What can injury to endothelial cells result in?
exposure of sub-endothelial collagen
what does fibrinogen get activated by?
chemicals the platelets release
an LAD CA thrombus can led to an MI. how will this present on ecg?
ST elevation on chest leads
how does cigarette smoke change vessel walls?
kills endothhelial cells
why does CO inhalation result in an increased risk of thrombosis?
inhaling lots of CO --> more rbc production --> more cells = blood more turgid --> can thrombus more easily
how does atherosclerosis disrupt laminar flow?
atherosclerosis= disease which causes plaque build-up in arteries
Causes arterial walls to become sticky
what is aspirin in low doses daily good for?
inhibits platelet aggregation
what is the most common cause of an embolus?
broken off thrombus travelling in the bloodstream
what is significant about IV drug abusers?
street heroin is often cut with talcum powder which isn’t v soluble
- -> injected emboli into veins
- -> usually filtered in lungs, sometimes liver
above what ml of air can cause an embolus?
150
what is the diff btwn ischaemia and infarction?
ischaemia = any reduction in blood flow infarction = death of cells due to severe lack of blood flow
What is atherosclerosis? what causes it?
Condition where arteries become clogged with plaque.
Caused by atheromas (pathology of arteries in which there is deposition of lipids in the arterial wall with surrounding fibrosis and chronic inflammation)
what is the predominant cause of myocardial infarction?
atherosclerotic plaques
list 3 risk factors for atheromas
- raised serum lipids
- hypertension
- diabetes mellitus
what is the linkage between high serum lipids and atherosclerosis?
lipids cause endothelial damage
what is the major process after endothelial damage (and with which cells)?
chronic inflammation - with macrophages/fibroblasts
name 3 factors that can reduce endothelial damage
- reduced lipids
- lowered BP
- stopping smoking
which drug can reduce the amount of platelet aggregation at the site of endothelial damage?
taking low dose aspirin
define atherosclerosis
narrowing of arteries due to plaque formation
what is the diff btwn atherosclerosis and arteriosclerosis?
- athero = narrowing of arteries due to plaque formation
- arterio = hardening of arteries
can u have a genetic predisposition to atherosclerosis?
Yes
when is complicated atherosclerosis usually seen?
later in life
what is significant about atherosclerosis?
it is mostly based on incremental episodes of endothelial cell damage over a LONG period of time eg decades