Mechanisms of Disease Flashcards
What are the cause of hypoxia?
-hypoxaemia, anaemia, Ischaemia, histiocytic
What are the causes of cell injury and death?
- hypoxia
- physical agent
- radiation
- Toxins
- Microorganisms
- immune mechanisms
- dietary insufficiencies
- genetic abnormalities
What does histiocytic mean?
Inability to utilise oxygen in cells due to disabled oxidative phosphorlytic enzymes
What principle structures are the target for cell damage?
Cell membranes
Nucleus/DNA
Proteins, structural and enzymes
Mitochondria
What are the changes in reversible, hypoxic injury?
Loss of activity of sodium potassium ATPase
Cell switches to anaerobic metabolism
Ribosomes detach from ER so protein synthesis is disrupted
What occurs in irreversible hypoxic injury?
Profound disturbances in membrane integrity
Massive cystolic accumulations of calcium
Potent enzymes attracted elf. ATPase, endonuclease, proteases
Continuation of lysosomal damage
What is ischaemic reperfusion injury?
Blood floe is returned to tissue which has been subjected to Ischaemia but isn’t yet necrotic, the damage sustained by the return of flow can be worse
Possible causes of injury in ischaemic reperfusion injury?
Increased production of oxygen free radicals
Increased number of neutrophils, more inflammation and increased tissue injury
Delivery of complement protein and activation of complement pathway
What do chemicals do in chemical injury?
Some chemical act by combining with cellular component e.g. Cyanamide binging to mitochondrial cytochrome oxidase inhibiting ET and OP
What are free radicals?
Are reactive oxygen species with a single unpaired electron in their outer shell, they are unstable and are very reactive
How are free radicals produced?
Chemical and radiation injury
Cellular ageing
Ischaemic reperfusion injury
High oxygen concentration
What do free radicals do that is bad?
Attack lipid in cell membranes causing lipid per oxidation
Damage protein and nucleic acids
Know to be mutagenic
What do free radicals to that is good?
Produced by leuocytes in immune systems oxidative burst
Used in cell signalling
What are heat shock proteins used for?
These are proteins which are concerned with the upkeep of cellular proteins e..g ubiquitin and aim to mend and maintain then retaining cell viability
What is seen under a light microscope during cell injury?
Cytoplasmic: Decreased pink staining of cytoplasm, increased blue staining due to detachment of ribosomes from ER Nuclear: Pyknosis, shrinkage Karryosensis, fragmentation Karryolysis, dissolution of nucleus
What is seen under a electron microscope during cell injury?
Reversible:
Swelling, cyctoplasmic blebs, clumped chromatin, ribosomes separated from ER
Irreversible:
Further cell swelling, nuclear changes, swelling and rupture of lysosomes, membrane defects, myelin figures, lysis of ER, amorphorosis densities in swollen mitochondria
Define oncosis
Cell death with swelling, the spectrum of changes that occur in injured cells prior to death
Define necrosis
The morphological changes that follow cell death in living tissue, largely due to progressive degrading action of enzymes in a lethally injured cell
Define apoptosis
Cell death induced by a regulated intracellular programme where a cell activates enzymes that degrade it’s own nuclear DNA and protein. Cell death with shrinkage, individual cell
State the main differences between necrosis/oncosis and apoptosis?
Apoptosis: Singer cells affected Cell shrinkage Pathological or physiological Membrane remains intact Internucelosmal DNA cleavage
Oncosis/necrosis:
Sheets of cells affected
Cell swelling
Always pathological
Membrane breaks down
Diffuse/random DNA damage
Name the types of necrosis?
Coagulative
Liquefaction
Caseous
Fat
Describe coagulative necrosis
Denaturation of proteins dominates over release of enzymes
Cellular architecture is preserved
Describe liquefaction necrosis
Enzyme degradation is greater than desaturation of proteins so see enzymatic degradation of tissues.
See massive neutrophil infiltration
Tissue becomes a viscous mass no and acute inflammation = pus
Describe caseous necrosis
Charcetersied by amphomorosis debris, cheesy appearance down microscope
E.g. TB
Describe fat necrosis
Destruction of adipose tissue, direct trauma to tissue so breast, acute pancreatitis,
What is gangrene?
Not a type of necrosis!
A clinical term used to describe what is visible to the naked eye and is seen in ischaemic limbs
What is dry gangrene?
Coagulative necrosis
What is wet gangrene?
Liquifactive necrosis normally due to infection and can lead to septicaemia
Give a physiological and pathological example of apoptosis
Physiological = embryogenesis, in the removal of webbing Pathophysiological = hepatits B (council man bodies), graft vs host disease
Describe intrinsic initiation of apoptosis
All apoptotic machinery is inside the cell -> mitochondria
Triggers include DNA damaged withdrawal of GF, hormones
1. Leads to increased mitochondrial permeability resulting in the release of cytochrome C from mitochondria
2. Cytochrome c interacts with APAF1 and Capase 9 to form an apoptdome that activates various downstream capases
3. This clear proteins, breaks up cytoskeleton and starts degradation of DNA
Describe extrinsic initiation of apoptosis
Cause by externa ligands!
- Ligands bind to death receptors
- Leads to Capase activation independent of mitochondria
Describe the final stage of apoptosis: degradation and phagocytosis
- Cells break down into membrane body fragments called apoptotic bodies
- Apoptotic bodies express molecules on their surface that induce their phagocytosis by neighbouring cells or phagosomes
Name the important apoptotic molecules
P53 Cytochrome C, APAF1, Capase 9 Trail, death ligand Trail - R, death receptor Capases
Describe the structural changes see in apoptosis under a light microscope
Apoptotic cells appear shrunken and eosinophilic
Cell shrinkage, chromatic condensation, Pyknosis, nuclear fragmentation
Describe the structural changes see in apoptosis under a electron microscope
Apoptotic cells show cytoplasmic stemming, this progresses to fragmentation into membrane bound apoptotic bodies which contains cytoplasm organelles and nuclear fragments
What are the modules release by injured or dying cells
Potassium, enzymes, myoglobin,
What is an infarction?
An area of tissue death causes by obstruction of a tissue blood supply
Define hypoxia
Oxygen deprivation
What causes an infarct?
Thrombosis, embolism, external compression of a vessel, twisting of vessels
When do we get white infarcts!
Occurs in solid organs which limits the amount of haemorrhaging, occlusion of end artery, coagulative necrosis, white due to lack of blood in tissue
When do do by get a red infarct?
Extensive haemorrhaging into dead tissue, so dual blood supply such as the lungs, numerous anastomoses, loose tissue so poor structural support for capillaries, previous congestion e.g. Congestive heart failure, raised venous pressure
Infarcts can have a range of consequences…
Tissue affected has an alternate blood supply
How quickly the ischaemia occurs
How vulnerable the tissue is to hypoxia
Oxygen content of blood
What are the main abnormal cellular accumulations?
Fluids
Pigments
Lipids
Proteins
What does abnormal accumulation of fluid indicate?
Vacuoles and hydrophobic bleeding
Osmotic disturbance severe cellular distress
What are the abdomen cellular accumulations: lipid
Steatosis: accumulation of TAG, seen in liver, caused by alcohol abuse, diabetes mellitus, obesity, toxins.
Cholesterol: seen under microscopic as foam cells acquired in hereditary hyperlipideamia
What are the abdomen cellular accumulations: protein
Seen as eosinophilic droplets or aggregates in the cytoplasm.
Mallorys hyaline, seen in hepatocytes in liver disease
Alpha 1 anti trypsin deficiency, alpha anti trypsin in liver cannot be packaged by ER therefore accumulates in organelle can get emphysema in lung tissue.
Name an exogenous pigments
Carbon/coal dust
Name endogenous pigments
Lipofusin: seen in ageing cells, sign of previous free radical injury + lipid perioxidation
Haemosiderin, derived from Hb is formed when there is systemic or local excess of iron
Bilirubin, a bile pigment when deposited in tissues (jaundice, haemolytic anaemia, abnormal liver function)
Describe dystrophic calcification
No abnormality in calcium metabolism a serum calcium concentration
Occurs in:
Area of dying tissue, atherosclerotic plaques, ageing or damaged heart values, tuberculous lymph nodes
Describe metabolic calcification
Calcium is deposited in tissue when there is hyerpcalcaemia secondary to disturbances in calcium
E.g. Increased secretion of PTH due to parathyroid gland tumorusm ectopic secretion of PTH-rp
Destruction of bone secondary to primary tumours of bone e.g. leukaemia, Paget’s disease
What happens as cellular ageing
Damage to cellular constituents, DNA, accumulate lipofusin pigment, abnormally folded proteins, decline to ability to replicate and replicative sensence -> telomere
What is aspirin action?
Is a drug that acetates platelets cycooxygenase and blocks platelets ability to make thromboxane A2 which is a substance that activates platelet aggregation.
What harmful effects does aspirin have?
Stimulates respiratory centre causing respiratory alkalilous and compensatory mechanisms include metabolic acidosis also interfere with carbohydrate, fat and protein metabolism, decreased platelet aggregation, GI bleeding
Define acute inflammation
Response in living tissue to injury whose purpose is to limit the tissue damage
What are the features of a true inflammation?
Innate, stereotypes, immediately, occurs in minutes/hours, resolves in a few days, early
What are the causes of acute inflammation? And the purpose of it?
Microbial infections Hypersensitivity reactions Physical agents chemicals Purpose is to protect and help prevent further damage
What are the macroscopic features of acute inflammation?
Redness, swelling, pain, heat
What are the microscopic features of acute inflammation and how do they relate to macroscopic ones?
Oedema, swelling
Vasodilation, swelling, redness, heat
Neutrophil margination and migration, swelling
In acute inflammation name the mediators responsible for increased blood flow
Histamine and prostaglandins
In acute inflammation name the mediators responsible for vascular permeability
Histamine, leukotrienes
In acute inflammation name the mediators responsible for neutrophil chemo taxis
Bacterial peptides, C5a, LTB4
In acute inflammation name the mediators responsible for phagocytosis
C3b
Describe the microscopic changes in acute inflammation and how they are brought about
- Changes in blood flow
- Infiltration of inflammatory cells
- Exudate on of fluid into tissue, starlings law
Describe oxygen dependant mechanism in acute inflammation
Produces superoxide and hydrogen peroxide
And H2O2 mydroperoxidase halide system produces HOCL
Describe oxygen independent mechanism in acute inflammation
Lysoenzyme and hydroyalases
Bacterial permeability increasing protein, BPI
Cationic proteins
Why does the exudation of fluid constituent an effective response to injury in acute inflammation?
Delivers plasma proteins to area of injury
Dilutes toxins
Increases lymphatic draining, delivering microorganisms to phagocytes and antigens to immune systems and lymph nodes
Why does the infiltration of cells an effective response to injury in acute inflammation?
Removes pathogenic organisms and neurotic debris
Why does vasodilation constituent an effective response to injury in acute inflammation?
Increases delivery and increases temperature
Why does pain and loss of function constituent an effective response to injury in acute inflammation?
Enforces rest and reduces chance of further traumatic damage
What are the systematic effects of acute inflammation?
Fever,
Leukocyte, increase in WBC content do blood
Acute phase response, decreased appetite, raised pulse rate, altered sleep pattern, changes in plasma concentrations of acute phase proteins
Describe the resolution of acute inflammation
- neutrophils no longer marginate
- vessel permeability returns to normal
- exudate drains to lymphatic
- fibrin is degraded by plasmin and other proteases
- neutrophils die, break up, carried away, phagocytosed
What is the mechanism behind resolution in acute inflammation?
All mediators have short half lives Maybe inactivated by degradation Maybe unstable Maybe dilute in the exudate Specific inhibitors of acute inflammatory changes e.g. Endothelium
Aorta from resolution what are the outcomes of acute inflammation?
Chronic inflammation -> absecss
GI, fibrous repair and tissue regeneration, death
What is labour pneumonia and what microorganism causes it?
A form of pneumonia that effects a large and continuous area of lobe of lung, see inflammation of lungs, exudate, breathless, hypoxic patients,
Caused by streptococcus pneumoniae
What is hereditary angio oedema?
Absence of C1 esterase inhibitor
Main clinical features are swelling on the lips, eyes, tonque
Define chronic inflammation
Chronic response to injury with associated fibrosis
When does chronic injury arise?
May take over form acute inflammation
May arise de novo
May develop alongside acute inflammation
What are the two most important cells in chronic inflammation?
Lymphocytes
Macrophages
What are the three types of giant cells that you can get?
Touton, foamy cytoplasm, neatly organised nuclei
Langerhans, multinucleated but nuclei in a peripheral horse shoe shape
Foreign body type, multinucleated, haphazard positioning of nuclei
What are possible, complication of chronic inflammation?
Fibrosis
Impaired function
Atrophy
Stimulation of an immune response
What is granulomatous inflammation?
Chronic inflammation with granuloma
What is the main cell type in a granuloma?
Main cell: epitheliod histiocytes, which are modified immobile macrophages
Lymphocytes
What are the main causes of granulomatous inflammation?
- mildly irritant foreign material
- infections: mycobacterium , leprosy, TB, syphyilis
- unknown causes, sarcoid, Crohn’s disease
Describe TB chronic inflammation
Cause by mycobacterium, produces number of toxins or lysis enzymes, See langerhans giant cells 1. Arrest, fibrosis scarring 2. Erosion into bronchioles 3. Tuberculous emphysema 4!. Erosion into the blood stream
Describe sarcoidosis inflammation
Idiopathic Causes small patches of red and swollen tissue grnwulomas Non cascating granulomatous, giant cell Lymph nodes and lungs involved Variables clinical maniefesto tins
Define resolution
Restoration of normality
Define regeneration
The replacement of dead or damaged cells by functional, differentiated cells. In order to maintains the size of a tissue or organ.
It can occur after injury if the harmful agent is removed and there is linked tissue damage.
What factors contribute to controlling regeneration?
- Growth factors, promote proliferation in stem cell population, expression of genes controlling cell cycle, Extracellular signals transduced into cell
- Contact between basement membranes -> signalling down by adhesion molecules, inhibits proliferation in intact tissue, so loss of contact promotes prliferation I.e. Contact inhibition
Define fibrous repair
The replacement of functional tissue by scar tissue
- occurs in necrosis of labile and stable cells if collage framework is destroyed or in necrosis of permanent cells
What are the three points in fibrous repair
- Cell migration of inflammatory cells, endothelial cells, fibroblast/myofibroblasts
- Angiogenesis
- Extra cellular matrix
What is the function of the extra cellular matrix in healing and repair?
Supports and anchors cell
Separates tissue comportment
Sequesters growth factors
Allows communication between cells facilities cell migration
What is Ethlers Danlos syndrome?
Defective conversion of procollagen to tropocollagen
What is alports syndrome?
Cause by defects in type IV collagen a major structural competent of the basement membrane in kidney, ear, eye. See he’s urea, progressive renal failure, hearing loss, chronic kidney disease
What controls fibrous repair?
Inflammatory cells are mediated by chemotaxis
Angiogenesis by platelets, GF -> VEGF, BEGF
Macrophages produce various pro fibrotic cytokines e.g. TNF
Describe the mechanisms of fibrosis repair (split into 3 stages)
- Inflammatory cells infiltrate
- blood clot forms and immediate protective layer
- acute inflammation around edges
- chronic inflammation, Macrophages and lymphocytes migrate into clot - Clot replaced by granulation tissue
- angiogenesis, capillaries and lymphatic is sprout and infiltrate
- myo/fibroblasts migrate and differentiate
- ECM is produced by them - Maturation
- cell proliferation falls
- collagen increase, matures and remodels
- myofibroblasts contract, reducing volume of defect
- vessels differentiate and are reduced
- > left with a fibrous scar