MoD Flashcards
How can cells become injured?
Radiation Extreme heat Hypoxia Microorganisms Chemical agents Trauma Immune mechanisms
What is disease?
A state of failed homeostasis resulting in morphological and functional changes to cells
What are the 4 types of hypoxia?
Hypoxic hypoxia - low pO2 atmosphere, low O2 uptake in lungs
Anaemic hypoxia - lack of Hb to carry the O2, CO binding to Hb
Ischaemic hypoxia - lack of blood supply and therefore O2 delivery to a tissue
Histiocytic hypoxia - malfunctioning oxidative phosphorylation pathway (action of CN etc)
What is the result of hypoxia?
No respiration and no ATP generated as a result =
1). Increase in glycolysis
- production of lactate, pyruvate etc lowers pH = clumping of chromatin
2). Ribosomes detach from ER
- decreased protein synthesis
- lipid deposition
3). Na+/K+ ATPase fails
- intracellular Na+ mounts, K+ efflux occurs and NCX reverses to bring in Ca2+
= cellular swelling, blebs, myelin figures
What effect does high intracellular Ca2+ have on a cell?
Activates enzymes
1) . Proteases = digests cytoskeleton and proteins
2) . Phospholipases = damage membranes including ER and lysosomes
3) . ATPases = rid of the small ATP levels present
4) . Endonucleases = damages chromatin
What is oncosis?
The spectrum of morphological changes in a cell, prior to its death that occurs with swelling.
What is necrosis?
The morphological changes that a cell undergoes after it has been dead some time.
What are the reversible/oncosis related changes that can occur in cell injury?
- Swelling - shows as reduced pink staining
- Chromatin clumping
- Blebs
- Ribosomes detaching from the ER - shows as bits of darker pink
What are the irreversible/necrosis related changes that occur in cell injury?
- karyolysis, pyknosis, karyorrhexis
- myelin figures
- further swelling
- lysosome and ER rupture
What is coagulative necrosis and its appearance?
Protein denaturation > enzymatic activity
Ghost outline of cells preserves cell architecture
Heart, kidney
What is liquefactive necrosis and what does it look like?
Enzyme degradation > protein denaturation
More liquified and possibly creamy (pus may be present if acute inflammation is ongoing) with debris and neutrophils
Brain, lungs
What is caseous necrosis and what does it look like?
This is often found in cases of TB
Structureless with debris, often appears white and soft (like cheese) and with granulomas
What is fat necrosis and what does it look like?
This is destruction of adipose tissue.
Appears chalky white (due to fatty acid reaction with calcium) and the outline of adipocytes are present.
What is an infarct?
Tissue death caused by obstruction of the tissues blood supply
In what types of necrosis do the different types of infarct occur in?
Red infarct can occur in liquefactive
White infarct can occur in coagulative
What is a white infarct and where/why does it occur?
Where there is little haemorrhage into the area of tissue death.
Occurs due to occlusion of an end artery and due to solidarity of the tissue (as white infarcts occur in solid organs) limiting haemorrhage into it.
Heart, spleen, kidneys (usually wedge shaped)
What is a red infarct and where/why does it occur?
This is where extensive haemorrhage occurs.
Occurs if
- the tissue has collateral blood supply (two arteries supplying it)
- the tissue is not solid (poor stromal support)
- the tissue has many anastomoses (2 arteries share a capillary bed)
- increased venous pressure
- congestion has been in the tissue previously
Occurs in the brain, lungs
What are the 2 reactions that form free radicals?
Haber Weiss
- O2- + H2O2 + H+ —–> O2 + *OH + H2O
Fenton reaction
- Fe2+ + H2O2 —–> OH- + *OH + Fe3+
Why are free radicals bad?
Damage DNA
Lipid peroxidation
Cause proteins to be denatured
What are some cellular defences against ROS?
- SOD and catalase (O2- —-> H2O2 —-> H2O + O2
- glutathione and NADPH
- Vit A, C, E and flavenoids (beta carotene)
- zinc and selenium in membrane as scavengers
What is ischaemia reperfusion injury caused by?
A build up of ROS, neutrophils and compliment proteins
What products do dying cells release?
K+
- hyperpolarisation of cells which makes it harder to fire A.P
- usually diluted before it reaches the heart but can be much larger in huge trauma, tumour lysis syndrome and tourniquet shock
Enzymes
- can be detected for diagnosis
Myoglobin
- released from damaged striated muscle (trauma, burns, exercise)
- plugs up renal tubules and can lead to renal failure = brown urine
What is calcification?
The accumulation of hydroxyapatite crystals in tissue, especially abnormal in soft tissue.
What is dystrophic calcification and where does it often occur?
Calcification in areas of dying tissue with no abnormality in Ca2+ levels or metabolism (= local)
Atherosclerotic plaque, ageing or damaged heart valves, TB infected lymph nodes
What is metastatic calcification and how does it occur?
This is where calcium is deposited into tissues due to hypercalcaemia as a result of abnormal metabolism.
Can occur as a result of
- increased PTH secretion due to ectopic producing tumour or parathyroid tumour
- bone destruction
- vitamin D related disorder
- renal failure
What are the basic steps of apoptosis?
Normal cell
Cell chromatin condenses
Cell shrinks
Formation of apoptotic bodies
What is the intrinsic pathway of initiation and execution of apoptosis?
Mitochondria increase permeability of membrane to allow leakage of cytochrome C
Cytochrome C reacts with APAF1 and caspase 9 to form an apoptosome
Apoptosome activates further caspases
What inhibits he release of cytochrome C from mitochondria?
BCl2
What is the extrinsic pathway for initiation and execution of apoptosis?
External death ligands bind to death receptors on the cell
This activates caspases
What is the third stage of apoptosis and how does it occur?
Degradation and phagocytosis
Apoptotic bodies have portions of cytoplasm and other organelle fragments inside them. They have an undamaged membrane containing molecules that induce their phagocytosis
What do caspases do?
Degrade the DNA and cytoplasmic proteins
Name some physiological and pathological pathways in which apoptosis occurs.
Physiological
- sculpting in embryogenesis
- some organs response to hormones (uterus etc)
Pathological
- accumulation of misfolded proteins cause ER stress = apoptosis
- virus induced
- damage to DNA
Name some abnormal protein accumulations.
Mallorys hyaline - keratin build up in liver in alcoholic liver disease as it can’t process them.
Alpha1antitrypsin - in alpha1antitrypsin disorder the liver misfolds the enzyme = can’t leave ER so stays there and no longer inhibits tissue breakdown in other organs
Name some abnormal pigment accumulations.
Exogenous - coal dust, tattoo ink.
Endogenous
- haemosiderin - derived from Hb, can be released due to leakage from stores, or deposited due to systemic overload.
- –> may be caused by hereditary haemochromatosis, where the intestine absorbs too much iron and deposits in in organs
- lipofuscin - brown pigment due to ROS causing lipid peroxidation, found with ageing
- bilirubin - deposited in tissues if produced in excess causing jaundice
Name lipid accumulations.
TAG build up in liver = steathosis
Cholesterol build up = stored as membrane bound droplets as its insoluble. This can then be absorbed by macrophages to form foam cells.
What are the effects of an aspirin overdose?
Increases resp centre = alkalosis which body tries to amend = acidosis
Interferes with carb, fat and protein metab = lactate/pyruvate/ketone body production = acidosis
Decreases platelet aggregation and inhibits stomach from producing mucus = GI bleeding
What is acute inflammation?
An innate, early and stereotyped response of living tissue to injury.
What can cause acute inflammation?
Hypersensitivity reaction Microbial infection Direct trauma Chemical agents Physical agents
What are the 3 basic stages of acute inflammation?
Vascular change 1 (v. short vasoconstriction followed by dilation)
Vascular change 2 (increased vessel permeability)
Cellular phase
What are the macroscopic features of acute inflammation?
Rubor - redness
Dolor - pain
Calor - heat
Tumor - swelling
What occurs in vascular change 1 of acute inflammation?
1) . Brief vasoconstriction to restrict any blood loss.
2) . Vasodilation of arterioles then capillaries occurs to increase blood flow and therefore delivery of platelets, complement, neutrophils and chemical mediators. It also increases temperature of the body in an attempt to slow bacterial enzyme action.
What occurs in the 2nd vascular change of acute inflammation?
1). Dilated vessels increase in permeability
= exudate leakage because
–> dilation = increased hydrostatic pressure
–> permeability leaks proteins = increased colloid osmotic pressure outside the vessel
Therefore oedema occurs.
What does the leakage of exudate result in?
Increased lymphatic drainage (ridding of microbes quicker)
Dilution of toxins
Increase n chemical mediator, fibrinogen etc delivery to tissues.
Stasis of blood in the vessel due to an increase in viscosity.
What chemical mediators increase blood flow in the vessel?
Histamine
Prostaglandins
What chemical mediators increase vessel permeability?
Histamine Leukotrienes TNF IL-1 VEGF
What occurs in the cellular phase of acute inflammation?
Neutrophils move into the tissues and phagocytose debris and pathogens in the inflamed area.
How do neutrophils enter tissues in the cellular phase of acute inflammation?
1) . They express ligands that are complementary to chemoattractants such as c5a, LTB4 and bacterial peptides.
2) . These chemo attractants form a gradient towards the tissue, which the neutrophils therefore follow via chemotaxis.
3) . Roll along endothelium until they alter their cytoskeleton to form a pseudopod, and digest the basement membrane to pass into the tissue.
What do the neutrophils do once in the tissue in acute inflammation?
They phagocytose pathogens, aided by opsonins such as c3b and Fc.
Do this by forming a phagosome, which then fuses with lysosomes to form a secondary lysosome. This kills the pathogen by:
- O2 dependant - use of H2O2, O2- or OHCl*
- O2 in dependant - use of hydrolases, lysozymes, defensins and bactericidal permeability increasing protein.
Where does histamine come from?
Mast cells, basophils and platelets.
What is histamine released in response to?
IL-1 Physical trauma C3a C5a Immunological reaction
What is the difference between a transudate and exudate?
Exudate is protein rich as it is fluid lost to inflammation.
Transudate is low in protein as it is fluid lost simply to hydrostatic pressure.
What chemical mediators are involved in phagocytosis?
C3b
Fc
What chemical mediators act as chemoattractants in neutrophil migration?
LTB4
C5a
Bacterial peptides
What are the 4 methods of vascular leakage and the chemical mediators that cause each?
1) . Cytoskeletal reorganisation - TNF and IL-1
2) . Endothelial contraction - histamine and leukotrienes
3) . Injury - direct or induced by action of leukocytes (ROS, enzyme leakage)
4) . Increase in transcytosis across endothelial cytoplasm - VEGF
What is vascular leakage helpful in acute inflammation?
Delivery of cells and fibrin = LOCALISATION OF PROBLEM
What are the main local complications of acute inflammation?
Pain
Loss of function
Swelling (could block tubes)
Exudate (could compress organs, cause pericarditis/serotinitis etc)
What are the systemic complications of acute inflammation?
Acute phase response (fever, decreased appetite, increased use and temp, increased blood conc of fibrinogen, CRP, alpha1 anti trypsin etc, leukocytosis)
What chemical mediators control leukocytosis and are released by fever?
Fever - releases prostaglandins, TNFalpha and IL-1
Leukocytosis occurs due to TNFalpha and IL-1
What can the results of acute inflammation be?
1) . Complete resolution if cellular architecture is undamaged
2) . Continued acute inflammation with chronic inflammation in severe persistant or repeated irritation.
3) . Develops into chronic inflammation with fibrous repair
How does acute inflammation stop?
Mediators have short half life so run out Mediators are diluted/washed away via exudate Mediators degraded (e.g. by heparinase) or bound to antiproteases. Lipoxins, endothelium and other chemicals inhibit changes acute inflammation cause.
What causes lobar pneumonia?
Streptococcus pneumonaie
What occurs in lobar pneumonia and how does this give the symptoms it does?
Bacteria cause acute inflammation in the alveoli = increase in vascular permeability by VEGF, IL-1, TNF, histamine, leukotrienes etc.
This causes exudate to fill the lungs, decreasing gas exchange = breathlessness, dry cough, hypoxia.
Fever also occurs as part of the acute phase response
What can cause acute appendicitis?
Blockage of the appendix (e.g. By gallstones)
Hypersensitivity reactions
What can the bad consequences of appendicitis be?
1) . Perforation of the appendix = leakage of purilent exudate = peritonitis/pericarditis
2) . Abcess may form = septicaemia
3) . Ulceration due to loss of usual mucosal surface.
When does an abcess occur?
When acute inflammation in solid tissue pushes its layers apart by producing exudate
What occurs in the centre of an abcess?
Liquefactive necrosis (pus)
Why can accesses be a problem?
They can compress or place pressure on other structures
= pain
= damage and therefore scarring of adjacent structures
What does alpha1 antitrypsin deficiency cause?
Deficiency in alpha1 antitrypsin = usually inhibits elastase
Therefore loss of it = elastic tissue broken down quicker
= emphysema in lung
= scarring in liver (liver sclerosis = thickens due to fibrosis)
What is chronic inflammation?
A chronic response of living tissue to injury with associated fibrosis.
How can chronic inflammation arise?
1) . De novo
- some autoimmune conditions
- chronic low level irritation
- chronic infection
2) . From acute inflammation
- that has severe persistence or repeated irritation
- that is taking too severe to be resolved in a few days
What cells are present in chronic inflammation?
Macrophages Lymphocytes Fibroblasts/myofibroblasts Plasma cells Eosinophils
What is the function of plasma cells and when do they become present?
A B lymphocyte that has differentiated to produce antibodies
Present 7-14 days into an immune response = considerable chronicity
What is the function of eosinophils in chronic inflammation?
Tackle
- Hypersensitivity reactions
- Parasite infection
- Some tumours
What is the function of fibroblasts in chronic inflammation and how are they recruited?
Produce collagen required for fibrosis
Recruited by macrophages
What is the function of lymphocytes in chronic inflammation and where does each type mature?
B
- mature in bone marrow
- differentiate to produce antibodies
T helper
- mature in thymus
- activate B cells and macrophages
T killer
- mature in thymus
- cytotoxic function to kill virus infected cells
- activated by cytokines released by macrophages
What can macrophages be inactivated by?
Kupffer cells of liver
Monocytes in blood
What are the functions of macrophages in chronic inflammation?
1) . Phagocytosis
- can also do this by forming giant cells
2) . Synthesis of
- cytokines (which activate T killer cells)
- proteases
- complement
- blood clotting factors
3). Antigen presentation
Describe the 3 types of giant cell.
LANGHAN
- horse shoe shaped
- common in TB
TOUTON
- clock face shaped
- foamy cytoplasm surrounds macrophages
- common in fat necrosis
FOREIGN BODY TYPE
- disorganised nuclei
Why do giant cells form?
To tackle debris/pathogens too large or stubborn for a single macrophage to phagocytose
What are the conditions caused by fibrosis due to chronic inflammation?
Chronic colecystitis
Gastric ulceration
What is chronic colecystitis?
Gall stones block the bile duct, damaging the mucosal surface (ulceration) and obstructing bile flow.
This causes repeated acute inflammation, resulting in it becoming chronic.
What is gastric ulceration and its causes?
Acute caused by drugs, chronic by helicobacter pylori.
Leads to chronic inflammation in the stomach which alters its mucosal surface = acid > mucosa
= ulceration
How is gastric ulceration treated?
Antibiotic (amoxicillin) or a PPI inhibitor (proton pump = decreased acid)
How is chronic colecystitis treated?
Surgery to remove the gallstones
What are the conditions due to chronic inflammation that result in altered function of the affected part?
Thyrotoxicosis (Graves’ disease)
Inflammatory bowel disease
What is thyrotoxicosis (graves disease)?
- autoimmune production of antibodies which stimulate TSH receptors = increased T3/4
- the antibodies a produced by plasma cells that originate from a chronic inflammatory response
What are the 2 types of inflammatory bowel disease?
Ulcerative colitis
- idiopathic
- diarrhoea, rectal bleeding
- more superficial
- treat via immunosurpressants or colonectomy
Crohn’s disease
- idiopathic
- diarrhoea, rectal bleeding
- transmural so may cause fistulae (abnormal connection of 2 mucosal surfaces) and strictures (tube narrowing)
- treat with hydration, specific diet and immunosurpressants
In what disease does chronic inflammation lead to atrophy?
Atrophic gastritis
- chronic inflammation where lymphocytes/plasma cells produce autoantibodies that kill stomachs parietal cells
= impair function as these produce HCl
What immunological disorder is due to chronic inflammation?
Rheumatoid arthritis
- chronic inflammation destroys joints in a localised manner.
- systemically, it can lead to amyloidoses.
Temperature via non steroidal antiinflammatories or a disease modifying antirheumatic (block action of damaging chemicals produced by antibodies)
In what disorder does chronic inflammation lead to a loss in function and fibrosis?
Cirrhosis
Can be caused by alcohol, drugs, infection by hepatitis B/C, immune attack or fatty liver disease. = chronic inflam.
This leads to fibrosis forming nodules and therefore loss of function.
Treat via lifestyle changes or a transplant.
