Mechanisms of Disease Flashcards
Name 8 causes of cell injury.
Hypoxia Toxins Heat Cold Trauma Radiation Microorganisms Immune mechanisms
What is hypoxia and what is a common cause?
Reduced O2 often caused by ischaemia
What are the reversible changes in hypoxia?
Decreased oxidative phosphorylation and ATP production
Increased anaerobic glycolysis
Decreased pH
Accumulation of Na+
Cell swelling via osmosis
Detachment of ribosomes leads to decreased protein synthesis
What are the irreversible changes in hypoxia?
Massive accumulation of intracellular Ca2+ resulting in mass enzyme activation
What are the reversible structural changes in cell injury?
Swelling Chromatin clumping Autophagy - cell self destruction Ribosome dispersal Blebbing
What are the irreversible structural changes in cell injury?
Nuclear changes - eg. pyknosis, karyorrhexis, and karyolysis
Lysosome rupture
Membrane defects
ER lysis
Define necrosis and apoptosis.
Necrosis - changes that occur after cell death in living tissue
Apoptosis - programmed cell death
Name 4 types of necrosis.
Coagulative
Liquefactive
Caseous
Fat
Explain coagulative necrosis.
More protein denaturation than enzyme release
Cellular architecture preserved creating ghost outline of cells - only lasts a few days before phagocytosis
Often caused by infarct in solid organs - eg. liver
Explain liquefactive necrosis.
More enzyme release than protein denaturation
Tissue is lysed and disappears
Often caused by infection
Occurs more commonly in loose tissue - eg. lungs
Explain caseous necrosis.
Tissue appears amorphous
Halfway between coagulative and liquefactive
If in the lung, likely to be TB
NEVER MENTION CASEOUS NECROSIS UNLESS TB
Explain fat necrosis.
Cell death in adipose tissue
Dead fat can break off in blood and cause embolism
What is gangrene? Explain the difference between wet and dry gangrene.
Clinical term for grossly visible necrosis.
Dry = coagulative
Wet = liquefactive
What is infarct and how can it be classified?
Necrosis due to ischaemia.
Can be white or red depending on amount of haemorrhage.
Explain the differences between white and red infarct.
White infarct - occlusion of an end artery, leaving the area completely devoid of blood, much like Voldemort’s soul.
Red infarct - there some collateral supply, which leads to congestion of blood in the damaged tissue.
Describe what you would see in apoptosis.
Cells appear shrunken and very eosinophilic (pink)
Chromatin condensation, pyknosis, nuclear fragmentation
Name the three stages of apoptosis.
Initiation
Execution
Degradation/phagocytosis
Describe the intrinsic and extrinsic pathways in apoptosis.
Intrinsic - all apoptotic machinery within cell. Caused by DNA damage, lack of growth factors/hormones etc.
Extrinsic - TRAIL and Fas bind to death receptors
Both lead to capsase activations (proteases which mediate apoptosis)
What can you see during degradation in apoptosis?
Cell breaks into membrane bound fragments called apoptotic bodies. These are phagocytosed.
Name 7 important mediators of apoptosis and their general function.
p53 - Guardian of the Genome - acts in response to DNA damage TRAIL - death ligand TRAIL-R - death receptor BcI-2 - inhibits cytochrome c release Caspase - effector molecule of apoptosis
Cytochrome C (from mitochondria), APAF 1 and caspase 9 form the apoptosome (protein which causes apoptosis)
Name and describe two reactions which produce free radicals.
Fenton rection - Fe2+ + H2O2 -> Fe3+ + OH- + *OH
Haber-Weiss reaction - O2- + H+ + H2O2 -> O2 + H2O + *OH
Name 5 causes of acute inflammation. Bitch.
Microbial infections Hypersensitivity reactions Physical agents Chemicals Tissue necrosis
List the cardinal signs of acute inflammation.
Calor - heat
Rubor - redness
Tumor - swelling
Dolor - pain
Also loss of function.
Outline the steps causing acute inflammation.
- Vasodilation
- Gaps form in endothelium
- Exudation
- Margination and emigration of neutrophils
- Migration and emigration of macrophages and lymphocytes
What are the chemical mediators of vasodilation in acute inflammation?
Histamine
Prostaglandins
C3a, C5a
What are the chemical mediators of increased vascular permeability in acute inflammation?
Histamine
Prostaglandins
Kinins
What are the chemical mediators of emigration of leukocytes in acute inflammation?
Leukotrines
IL-8
C5a
Describe the action of neutrophils in acute inflammation.
Phagocytosis of microorganisms
Release toxic enzymes and metabolites causing damage to host tissue - eg. ROS
Name some chemical mediators for chemotaxis of neutrophils.
C5a
Cytokines
Bacterial peptides and LTB4 too
What are the symptoms of the acute phase response?
Decreased apetite
Raised HR
Altered sleep patterns
Changes in plasma conc. of acute phase proteins - eg. CRP, fibrinogen, α1-antitrypsin
What are the causes of fever in acute inflammation?
Endogenous pyrogens - IL-1, TNF-α, prostoglandins
What are the causes of leukocytosis in acute inflammation?
IL-1 and TNF-α produce accelerated release from marrow.
Macrophages and T lymphocytes produce colony stimulating factors (causes proliferation and differentiation)
What are the possible outcomes of acute inflammation?
- Complete resolution
- Continued acute inflammation with chronic inflammation
- Chronic inflammation and fibrous repair, with probable tissue damage
- Death
What factors help stop acute inflammation?
Mediators have short half-lifes and may be inactivated by degradation, dilution in exudate or inhibition.
Describe the changes that occur during resolution in acute inflammation.
Vascular changes stop Neutrophils no longer marginate Vessel permeability and calibre return to normal Exudate drains via lymphatic system Fibrin is lysed by plasmin Neutrophils die
When is resolution during acute inflammation possible?
If tissue architecture is intact, regeneration is possible.
What are some possible complications of acute inflammation?
Swelling - can block tubes/compress vital structures Shock (loss of fluid) Pain and loss of function Chronic inflammation Tissue damage
Describe what happens in blistering.
Caused by heat, sunlight, chemicals, etc.
Symptoms are pain and profuse exudate.
Collection of fluid strips off overlying epithelium.
Clear exudate (few cells).
Normally leads to resolution/scarring.
Describe what happens in an abscess.
Happens in solid tissue where inflammatory exudate forces tissue apart.
Liquefactive necrosis in center
Can cause high pressure, pain, and tissue damage.
Describe what happens in pericarditis.
Inflammation of the serous cavity of the pericardium
Increased pressure on heart
Can lead to cardiac tamponade.
Describe hereditary angio-oedema.
Deficiency of C1 inhibitor which inhibits bradykinin
Uninhibited bradykinin caused increased vascular permeability leading to oedema
Treat with C1 inhibitor
Describe α1-antitrypsin deficiency.
α1-antitrypsin inhibits elastase
Uninhibited elastase breaks down elastic tissue in lungs and liver
Causes emphysema and liver sclerosis
Describe chronic granulomatous disease.
Recessive sex linked
Immune phagocytes unable to form ROS, so some bacteria can’t be killed
Leads to excessive granuloma formation.
What is the difference between exudate and transudate?
Exudate - fluid loss in inflammation - high protein
Transudate - fluid loss due to hydrostatic pressure
Explain the action of some drugs used to treat acute inflammation.
NSAIDs (eg. aspirin and ibuprofen) - inhibit prostaglandin formation
Corticosteroids - immunosupressants decrease inflammation
