Pathological Processes Flashcards
Tissue removed from a living organism will die. It immediately undergoes changes that destroy the microscopic structure when blood supply is cut off. What are these changes called?
Autolysis (self digestion)
What causes autolysis?
Release of enzymes from lysosomes inside cells. The enzymes digest the cells from within, the cell bursts and enzymes damage the extracellular tissue.
Destroys cells and tissue architecture
What is the name given to a substance that has the ability to block the biochemical changes of autolysis?
Fixative
Give an example of a routine fixative used in pathology labs.
Formalin (10% solution of formaldehyde in water)
Fix for 24-48 hours
What is a cassette?
Samples of tissue are placed in a cassette. This is about the size of a stamp and has little slots. They are placed in racks of formalin which penetrates the cassette to bathe the tissue without allowing the tissue to escape.
What is embedding?
An embedding agent (eg. paraffin wax) hardens the tissue.
Why is the tissue dehydrated before being hardened with paraffin wax?
Wax does not mix with water so alcohol is used to dehydrate the tissue replacing the water in cells with alcohol. Xylene is then added which removes the alcohol.
Why are sections of tissue that are to be viewed by a microscope cut very thinly?
So light can pass through the tissue when we look at it down a microscope. Generally, the thinner you cut the section, the more detail we can see in the tissue.
What is disease?
A pathological condition of a body part, organ or a system Result of failed homeostasis---> Morphological changes in cells---> Function disturbances---> Identifiable group of signs/symptoms
Study of:
Intrinsic abnormalities - genetic
External factors - acquired eg. Infection
What does all disease begin with?
Molecular or structural alterations in cells.
What is medical microbiology?
Study of infectious disease and the organisms responsible for them in its broadest sense.
What is chemical pathology?
Study and diagnosis of disease from the chemical changes in tissues and fluid
What is haematology?
Study of blood disorders.
What is immunology?
Study of the specific defence mechanisms of the body.
What are the two main branches of cellular pathology?
Histopathology
Cytology
What is diagnostic pathology?
The study of structural and functional alterations in cells and tissues (eg. By microscopy) in order to arrive at a diagnosis.
What is the difference between histopathology and cytopathology?
Histopathology- investigation and diagnosis of disease from macroscopic and microscopic assessment of tissue samples (can see architecture)
Cytopathology-investigation and diagnosis of disease from microscopic assessment of isolated cells eg. Pleural effusion, smear tests
List some clinical uses of histopathology.
Core biopsies
Cancer resection specimens
Excised skin lesions
Endoscopic biopsies
List some clinical uses of cytopathology.
Fine needle aspirates of:
- breast
- thyroid
- salivary glands
- lung
- effusions (pleural and cardiac)
- cervical smears
- sputum
- urine
Why might cytology be used instead of histology?
Faster and cheaper Non-invasive/minimally invasive and safe Can be used for cells in fluids Sometimes a preliminary test before investigations or more tissue is taken for histology Used to confirm/exclude cancer/dysphasia
Why might histology be used instead of cytology?
Often therapeutic as well as diagnostic (eg. lesion of cancer completely removed)
Can assess architecture as well as cellular atypia
Can differentiate invasive from in situ malignancy
Can provide info on completeness of excision and more complete info on grading/staging
Better for immunohistochemical and molecular testing
Lower inadequate and error rates
What is cellular atypia?
Structural abnormality of a cell
What are ascites?
Fluid in abdomen
What questions should histopathogists ask to arrive at a diagnosis?
– Is this normal or not?
– Is this inflammatory or neoplastic?
– Is this benign or malignant?
– Is this a primary tumour or a metastasis?
When it is cancer, what can histopathologists tell us?
Type of cancer
Grade of cancer
Stage of cancer TNM
Completeness of excision and if margins are involved, which ones
Likely efficacy of further treatments eg. HER2 receptor presence—>herceptin treatment
All of which influence decisions on further treatment and management
What are the roles of fixative in tissue preparation? (3)
Inactivate tissue enzymes + denature proteins
Prevent bacterial growth
Harden tissue
After the tissue has been fixed, the specimen is examined and cut up by a _________. Samples are taken and placed into a __________
Pathologist
Cassette
How do you get tissue into a piece of wax that can be cut?
Blocking-Tissue taken out of cassettes by hand and put into metal blocks. Molten paraffin wax is added and allowed to harden. Metal tray is removed.
What is used to cut tissue into very thin sections before being viewed by a microscope?
A microtome
What stain is usually used to stain tissue during tissue preparation?
H&E
Haematoxylin- stains acidic components of tissue (nuclei) purple
Eosin- stains basic components of tissue (cytoplasm and CT) pink
During tissue preparation, how is tissue preserved and protected after staining?
Mounting- mounting medium is applied to the slide. Coverslip is put on top. Mounting medium dries and hardens, preserving the tissue and attaching the coverslip.
What is immunohistochemistry?
Demonstrates substances in/on cells by labelling them with specific antibodies. Antibodies are bound to enzymes that catalyse a colour changing reaction when then the antibody is bound to its receptor. (Brown stain)
Give some examples of substances that can be detected by immunohistochemistry. (4)
Any substance that is antigenic can be detected:
– Contractile protein actin, identifies smooth muscle cells
– Cadherins, cell adhesion molecules, deficient in some carcinomas, e.g. lobular breast carcinoma
– Hormone receptors, e.g., ER, PR, Her2 receptor (growth factor receptor) predicts response of breast cancer to Herceptin
– Microorganisms, e.g., CMV, HPV, herpes simplex
-Cytokeratins-give information about primary site of carcinoma
How can you find out which tissue a cancer originated in?
Immunohistochemistry for specific cytokeratins found in epithelia.
Cytokeratins act as markers for epithelial differentiation and show
tissue-specific distribution in epithelia.
Therefore, they give information about the primary site of a carcinoma, particularly when used in combination.
What is molecular pathology?
The study of how diseases are caused by alterations in normal cellular molecular biology. This can be due to altered DNA, RNA or protein, but most often molecular pathology refers to changes in DNA.
Give the steps involved in tissue preparation preceding light microscopy. (9)
- Fixation with formalin
- Cut-up (trimming)
- Embedding in paraffin wax
- Blocking
- Microtomy
- Staining
- Mounting
- Microscopy
Give the steps involved in tissue preparation for a frozen section.
- Rapidly freeze small piece of fresh tissue in a cryostat.
- Microtomy
- Staining
- Mounting
- Microscopy
Why is preparing frozen sections quicker than preparing tissue in the usual manner?
Skips fixation and embedding
When are frozen sections used?
Establishing the presence and nature of a lesion while the patient is still under anaesthetic
Only used when the result will influence the course of operation.
What are the disadvantages of using frozen sections rather than routine paraffin wax embedded sections?
- More difficult to interpret
- Errors and false negatives can occur-correct diagnosis is about 96% of cases. Errors due to misinterpretation of frozen section or because lesion of interest is not present in tissue submitted for frozen section.
What does the degree of cell damage depend on?
Type of injury
Duration of injury/Severity of injury
Type of tissue-neurones can only survive a few minutes before they suffer serious damage whereas fibroblasts can survive a few hours
What can cause cell injury? (6)
- Hypoxia
- Physical agents
- Chemical agents and drugs
- Microorganisms
- Immune mechanisms
- Dietary insufficiency and dietary excess
- Genetic abnormalities
What are the different types of hypoxia? (4)
Hypoxaemic hypoxia
Anaemic hypoxia
Ischaemic hypoxia
Histiocytic hypoxia
What type of hypoxia does cyanide poisoning lead to?
Histiocytic hypoxia - inability to utilise oxygen in cells due to disabled oxidative phosphorylation enzymes. Cyanide binds to mitochondrial cytochrome oxidises.
What type of hypoxia does CO poisoning lead to?
Anaemic hypoxia- reduced ability of haemoglobin to carry oxygen
What type of hypoxia does lung disease eventually cause?
Hypoxaemic hypoxia- arterial content of oxygen is low due to reduced absorption of oxygen in the lungs.
What is ischaemic hypoxia and what can cause it?
Lack of oxygen due to interruption in blood supply caused by:
Blockage of a vessel
Heart failure
What is the difference between ischaemia and hypoxia?
Ischaemia is caused by interruption to blood supply to a region depriving it of oxygen and other nutrients.
Hypoxia is lack of oxygen to a region.
Ischaemic hypoxia is lack of oxygen to a region due to interruption to blood supply.
What can cause hypoxaemic hypoxia? (2)
Reduced inspired partial pressure of oxygen at high altitudes
Reduced absorption of oxygen secondary to lung disease.
Why is more fatal if blood supply is cut off to the brain than if blood supply is cut off to the dermis of the skin?
Brain tissue will suffer a greater degree of injury than skin tissue.
Neurones can only survive a few minutes with hypoxia whereas fibroblasts in the dermis of the skin can survive a few hours.
What is Hives an example of?
A hypersensitivity reaction
host tissue is injured secondary to an overly vigorous immune reaction
What is Grave’s disease of thyroid an example of?
An autoimmune reaction
Immune system fails to distinguish self from non-self
What are the two ways in which immune mechanisms can cause cell injury?
Hypersensitivity reactions-host tissue is injured due to an overly vigorous immune reaction eg. Hives
Autoimmune reactions-immune system fails to distinguish self from non-self eg. Grave’s disease of thyroid
What are the targets of cell injury? (4)
- Cell membranes- fragile
- Nucleus- site of DNA
- Proteins- structural proteins and enzymes
- Mitochondria- site of oxidative phosphorylation
What is happening at a molecular level in hypoxia to cause reversible hypoxic injury?
Cell is deprived of oxygen.
Mitochondrial ATP production by oxidative phosphorylation stops. Less ATP in cell causes:
1. ATP-driven Na+/K+ pump inhibition—> Na+ and water influx—> the cell swells and the plasma membrane is stretched/RER swelling/loss of microvilli
2. Rate of glycolysis increases to produce ATP until glycogen stores deplete —> drop in pH—> clumping of nuclear chromatin
3. Detachment of ribosomes from RER—> decreases protein synthesis—> lipid deposition (particularly in hepatocytes)/the cell initiates a heat shock (stress response) which probably will not be able to cope if hypoxia persists
What is the marker of irreversible hypoxic injury?
Large influx of Ca2+ into the cell.
What happens in prolonged hypoxia to cause irreversible cell damage?
- Large influx of calcium into the cytosol mainly from intracellular compartments but also from extracellular environment as NCX reverses. Calcium activates:
1. Phospholipases- cell membranes lose phospholipids
2. Proteases- damage cytoskeletal structures and attack membrane proteins
3. ATPase- causing further loss of ATP
4. Endonucleases- breaks down DNA - ER and other organelles swell. Enzymes leak out of lysosomes and digest cytoplasmic components.
- Damaged cell membranes start to show blebbing and at some point the cell dies, possibly by the burst of a bleb.
Why is calcium toxic to cells?
Calcium activates:
• phospholipases- causing cell membranes to lose phospholipid
• proteases-damage cytoskeletal structures and attacking membrane proteins
• ATPase- causes further loss of ATP
• endonucleases-breaks down DNA and causes the nuclear chromatin
What are free radicals?
Free radicals are reactive oxygen species. They have a single unpaired electron in their outer shell. This is an unstable configuration so they react with other molecules, often producing further free radicals.
What are the three most biologically important free radicals?
OH• (hydroxyl) (the most dangerous)
02- (superoxide)
H202 (hydrogen peroxide).
When are free radicals produced?
- Free radicals are particularly produced by:
- Normal metabolic reactions eg. Oxidative phosphorylation
- Inflammation: oxidative burst of neutrophils
- Radiation : H20 –>OH•
- Contact with unbound metals within the body: iron and copper Clinical relevance: free radical damage occurs in Wilson’s disease and haemachromatosis
- Drugs and chemicals eg. In the liver, during metabolism of paracetamol or carbon tetrachloride by P450 system
- Ischaemia-reperfusion injury
- Cellular ageing
- High oxygen concentrations.
What is the body’s mechanism of defence against free radicals?
- Free radical scavengers donate electrons to the free radical: vitamins A C E
- Metal carrier and storage proteins (transferrin, ceruloplasmin) sequester iron and copper (these transition metals form free radicals)
- Enzymes neutralise free radicals: superoxidase dismutase, catalase, glutathione peroxidase
When do free radicals injure cells?
When there is greater free radical production than free radical scavenging so free radicals build. The cell or tissue is now in oxidative stress.
What types of cellular structures are damaged by free radicals?
• CELL MEMBRANE Attack lipids in cell membrane—>Lipid peroxidation, further generation of free radicals (autocatalytic chain reaction)
• Oxidise proteins, carbohydrates and nucleic acids—> molecules become bent out of shape, broken or cross-linked—>mutagenic/carcinogenic
Why are free radicals considered to be carcinogenic?
They oxidise nucleic acids.
Cause DNA molecules to become bent out of shape/broken or cross-linked.
This leads to mutations and can cause cancer depending what gene this mutation is in (p53 important).
How are heat shock proteins involved in the cellular stress response?
When cells are submitted to stress, they turn down protein synthesis of their usual proteins and increase synthesis of heat shock proteins.
Heat shock proteins maintain protein viability by refolding and correcting proteins and thus maximise cell survival.
What are unfoldases and chaperonins examples of?
Heat shock proteins
Synthesis of heat shock proteins is triggered by…
ANY form of injury - not just heat
Why are reactive oxygen species in a haemorrhage?
Blood released. Iron released from haemoglobin. Contact of unbound iron with free radicals produces more reactive oxygen species.
What cellular changes appear in oncotic/necrotic cells that are injured/dying as a result of hypoxia that can be viewed with a light microscope?
Cytoplasmic changes
Nuclear changes
Abnormal intracellular accumulations
How can you tell if a cell is injured (reversible injury) or dead (irreversible injury) using a light microscope?
HINT- cytoplasmic changes
Injured cells- cytoplasm is pale and swollen (high water content due to Na+ influx)
Dead cells- cytoplasm is stained deeply pink (proteins have denatured and coagulated)
What are the different types of nuclear changes that can be seen with a light microscope in dead cells?
Pyknosis - nucleus shrinks and becomes very dark
Karyorrhexis- nucleus breaks up into different bits
Karyolysis- nucleus disappears
Karyorrhexis and karyolysis are characteristic of apoptosis.
In a cell that has suffered reversible cell damage, what are the cellular changes that can be seen with an electron microscope?
• Swelling – both of the cell and the organelles due to Na+/K+ pump failure
• Cytoplasmic blebs, which are symptomatic of cell swelling and proteases are breaking down cytoskeleton
• Clumped chromatin due to reduced pH
• Ribosome separation from the endoplasmic reticulum due to failure of energy-dependant process of maintaining ribosomes in the correct location
In a cell that has suffered irreversible cell damage, what are the cellular changes that can be seen with an electron microscope?
• Increased cell swelling
• Nuclear changes - pyknosis, karyolysis, or karyorrhexis
• Swelling and rupture of lysosomes – reflects membrane damage
• Membrane defects
• The appearance of myelin figures (which are damaged membranes)
• Lysis of the endoplasmic reticulum due to membrane defects
• Amorphous densities in swollen mitochondria
What is the best method to diagnose cell death?
Die exclusion test- cells that take up the dye are dead as their membranes are damages. Cells that do not stain are not dead.
Testing function is better than looking at the cell down a microscope because it is often difficult to distinguish between cells that have undergone reversible injury and irreversible injury (death).
What is oncosis?
The spectrum of changes that occur prior to cell death by swelling in cells injured by hypoxia and some other agents.
What is necrosis?
Morphological changes that occur after a cell has been dead for some time (4-24 hours).
Not a type of cell death- appearance not a process.
What are the types of necrosis?
Coagulative
Liquifactive
Caseous
Fat necrosis
What is coagulative necrosis?
Morphological changes in cell death caused by swelling and protein denaturation (hence clumping).
What is liquifactive necrosis?
Morphological changes in cell death caused by swelling and dissolution of proteins by enzymes.
Where do we see coagulative necrosis?
Ischaemia of solid organs (organs that have a lot of CT support)
Eg. Kidneys
Where do we see liquifactive necrosis?
- Ischaemia of loose tissue (organs without much CT support) Eg. Brain
- Inflammation with lots of neutrophils
What does coagulative necrosis appear like under a light microscope?
Denaturation of proteins>enzyme degradation
Ghost outline of cells- cellular architecture is somewhat preserved.
What does liquefaction necrosis appear like under a light microscope?
Enzyme degradation of proteins> protein denaturation
Leads to enzymatic digestion of tissues
Cannot recognise what the tissue was- NO ghost outline of cells. Can see liquid with naked eye.
What is caseous necrosis?
Enzymatic dissolution of proteins = denaturation of proteins
In between coagulative and liquifactive necrosis
What does caseous necrosis appear like under a light microscope?
Structureless debris
When do we see caseous necrosis?
Tuberculosis (in lungs)
What is fat necrosis?
Death due to swelling of fat cells.
Why can pancreatitis be detected by radiography?
Acute inflammation and injury to pancreas
Membrane integrity of cells is lost and pancreatic enzymes escape.
Lipases digest fat in the abdomen and produce fatty acids.
Fatty acids that are produced react with calcium and form calcium soaps.
Calcification is shown on X-rays
When does fat necrosis occur?
Pancreatitis
Breast due to trauma-forms a very hard lump in the breast
A hard lump in the breast can form due to:
Cancer
Fat necrosis
Pathologists can differentiate between the two.
What does gangrene mean?
Necrosis visible to the naked eye. (An appearance of necrosis).
What is the difference between dry and wet gangrene?
Dry gangrene
Necrosis modified by exposure to air
Underlying process: coagulative necrosis
Wet gangrene
Necrosis modified by infection
Underlying process: liquifactive process
What is gas gangrene?
Wet gangrene where tissue is infected with anaerobic bacteria that produces visible and palpable bubbles of gas within tissues.
What does infarction mean?
Necrosis caused by reduction in arterial blood flow- ischaemia. (A cause of necrosis, can result in gangrene).
The underlying process of wet gangrene is…
Liquifactive necrosis
The underlying process of dry gangrene is…
Coagulative necrosis
Why are some infarcts white?
Anaemic Solid organs (good stromal support) after occlusion of an end artery (terminal sole artery to an organ)
What is an infarct?
An area of necrotic tissue which is the result of loss of arterial blood supply (An area of ischaemic necrosis).
What are the causes of infarction?
Common:
Thrombosis- blood clot
Embolism- bit of a thrombus has broken and travelled in artery and has blocked off supply elsewhere
Others:
External pressure on arteries eg. Testicular torsion. See lecture for pictures with examples.
Why are some infarcts red?
Haemorrhagic
Organs with dual blood supply. Eg. Lungs (systemic and pulmonary artery)
Organs with collateral blood supply eg. Bowel (numerous anastomoses)
Raised venous pressure
Re-perfusion
What do the consequences of an infarction depend on?
- Alternative blood supply
- Speed of ischaemia (more serious if faster)
- Tissue involved (more serious if in brain than in feet)
- Oxygen content of the blood (more serious if anaemic to begin with)
What is ischaemic-reperfusion injury?
If blood flow is returned to an ischaemic but not yet necrotic tissue, damage sustained can be worse than if blood flow hadn’t been returned.
What are the causes of ischaemic reperfusion injury?
Increased production of oxygen free radicals
Increased number of neutrophils resulting in more inflammation/tissue injury
Delivery of complement proteins and activation of the complement pathway
What does ischaemic reperfusion injury cause in the heart?
Arrhythmia
What important substances are released by injured cells?
Potassium - disrupts electrical activity of the heart
Enzymes- indicate the organ involved, extent, timing and evolution of tissue damage
Myoglobin- released from dead striated muscle (cardiac and skeletal)
What are the mechanisms of cell injury? (5)
- Reversible hypoxic cell injury
- Irreversible hypoxia cell injury
- Ischaemia-reperfusion injury
- Cyanide poisoning
- Free radicals
What happens when there is myoglobin in the blood?
1.Myoglobin blocks glomerus of kidney—>
Renal failure
2. Passes into urine—>Brown urine
What is rhabdomyolysis?
Death of skeletal muscle fibres leading to the release of myoglobin into the blood stream.
What is apoptosis?
Cell death with shrinkage is the death of a single cell (or small cluster of cells) due to activation of an internally controlled suicide programme where a cell activates enzymes that degrade its own nuclear DNA and proteins.
When does apoptosis occur pathologically?
Cytotoxic T cell killing of virus-infected or neoplastic
cells
When cells are damaged, particularly with damaged DNA
Graft versus host disease
Describe the appearance of an apoptotic cell under a light microscope.
shrunken
intensely eosinophilic
Chromatin condensation, pyknosis and karyorrhexis are seen and these take on a distinctive appearance in apoptosis.
Describe the appearance of an apoptotic cell under an electron microscope.
cytoplasmic budding (not blebbing as is seen in oncosis) which progresses to fragmentation into membrane-bound apoptotic bodies which contain cytoplasm, organelles and often nuclear fragments The apoptotic bodies are eventually removed by macrophage phagocytosis. No leakage of cell contents occurs and therefore apoptosis does not induce inflammation.
When is apoptosis initiated by the intrinsic pathway?
The initiating signal comes within the cell:
- irreparable DNA damage
- withdrawal of growth factors/hormones
When is apoptosis initiated by the extrinsic pathway?
Initiated by extracellular signals:
- Cells that are a danger eg. Tumour cells/virus-infected cells
- TNFa secreted by T killer cells. Binds to cell membrane receptor and activates caspases
What is the role of p53 protein and cytochrome C in apoptosis?
Activation of the p53 protein causes the outer mitochondrial membrane to become leaky. Cytochrome C is released from the mitochondria and this causes the activation of caspases.
What are the differences between apoptosis and oncosis?
Oncotic affects a group of contagious cells whereas apoptosis affects single cells.
Oncosis causes swelling of cells whereas apoptosis causes shrinkage of cells.
In oncosis, nuclear changes can be seen as: pyknosis, karyorrhexis and karyolysis. In apoptosis, fragmentation of DNA into similar sized fragments occurs to form clumps beneath the nuclear membrane and generally shows: pyknosis or karyorrhexis.
In oncosis, the plasma membrane is disrupted whereas in apoptosis, the plasma membrane remains intact.
In oncosis, cellular contents are digested by enzymes or leak out of the cell whereas in apoptosis, cellular contents are released in apoptotic bodies.
Oncosis causes inflammation whereas apoptosis does not.
Oncosis is always pathologic, whereas apoptosis can be physiological or pathological.
Why are abnormal cellular accumulations found in injured cells?
Cell injury can cause:
Abnormal metabolism
Alterations in protein folding/transport
Deficiency of critical enzymes
Inability to degrade phagocytised particles
What are the main types of intracellular accumulations in injured cells? (5)
- Water and electrolytes
- Lipids
- Proteins
- Pathological pigments
- Carbohydrates
What clinical condition is caused by accumulation of triglycerides in cells?
Which organ is this seen in?
Steatosis - often sen in the liver as this is the major organ of fat metabolism.
What are the common causes of liver steatosis?
Alcohol
Diabetes mellitus
Obesity
Toxins
Why is it relatively easy for cholesterol to accumulate?
Cannot be broken down and is insoluble
Can only be eliminated through the liver
Excess stored in cell vesicles
Which cells does cholesterol accumulate in forming atherosclerotic plaques (foam cells)?
Macrophages
Describe how α1-antitrypsin deficiency causes accumulation of proteins in cells.
Liver produces incorrectly folded α1-antitrypsin protein
These cannot be packaged by the ER so the unfolded enzyme accumulates within the ER and is not secreted.
What is haemosiderosis?
Haemosiderin is an iron storage molecule which is derived from haemoglobin. Forms when there is a systemic or local excess of iron eg. Bruise
With systemic overload of iron, haemosiderin is deposited in many organs.
This is seen in catalytic anaemias, blood transfusions and hereditary haemochromatis.
What disease causes the skin to look tanned and was previously known as ‘bronze diabetes’?
hereditary haemochromatosis
Genetically inherited disorder
Results in increased intestinal absorption of dietary iron
Iron is deposited in skin, liver, pancreas, heart and endocrine organs.
Therefore symptoms include liver damage, heart dysfunction, multiple endocrine failures.
How can a blocked bile duct cause jaundice?
Accumulation of a bright yellow pigment - bilirubin.
This is a breakdown product of heme- stacks of porphyria rings.
Formed in all cells of the body as cytochromes contain heme but must be eliminated in bile.
Taken from tissues by albumin to liver, conjugated with bilirubin and excreted in bile.
If bile flow is obstructed or overwhelmed, bilibrubin in blood rises and jaundice results.
Bilirubin is deposited in tissues extracellularly or in macrophages
What are the two different types of pathological calcification?
Dystrophic calcification
Metastatic calcification
What is the difference between dystrophic calcification and metastatic calcification?
Dystrophic- localised
Occurs in an area of dying tissue, in atherosclerotic plaques, in ageing or damaged heart valves, in TB lymph nodes
Metastatic calcification-generalised
Occurs throughout the body
Why does dystrophic calcification occur?
No abnormality in calcium metabolism or serum calcium or phosphate concentrations
Local change/disturbance favours nucleation of hydroxyapetite crystals
What can dystrophic calcification lead to?
Organ dysfunction
Eg. Calcified heart valves—> heart failure
Why does metastatic calcification occur?
Hypercalcaemia secondary to disturbances in calcium metabolism
Hydroxyapetite crystals are deposited in normal tissues throughout the body
What causes hypercalcaemia?
Increased secretion of parathyroid hormone (PTH) resulting in bone resorption:
•Primary - due to parathyroid hyperplasia or tumour •Secondary – due to renal failure and the retention of
phosphate
•Ectopic - secretion of PTH-related protein by malignant tumours (e.g., carcinoma of the lung)
Destruction of bone tissue:
• Primary tumours of bone marrow, e.g., leukaemia, multiple myeloma
• Diffuse skeletal metastases
• Paget’s disease of bone – when accelerated bone turnover occurs
• Immobilisation
What enzyme do many cancer cells have that gives them the ability to replicate multiple times?
Telomerase
What is inflammation?
The response of vascularised living tissue to injury
What is the purpose of inflammation?
To deliver defensive materials (leucocytes, plasma proteins and fluid) to a site of injury. It aims to:
-protect the body against infection (particularly bacterial infection)
-to clear damaged tissue
-to initiate tissue repair
IN ORDER TO…
Limit tissue damage
What are the properties of acute inflammation?
Rapid response - hours to days
Innate
Stereotyped
How is inflammation controlled?
Chemical mediators
List some of the major causes of acute inflammation. (6)
Microbial infections
Acute phase hypersensitivity reactions
Physical agents
Chemicals
Tissue necrosis
Foreign bodies
What are the characteristic clinical signs of acute inflammation? (5)
Rubor Tumour Calor Dolor Loss of function
What prevents inflammation from happening all the time?
Every mediator has inhibitors
The duration of inflammation is limited as mediators have short lives (seconds to minutes) and their effects last minutes to hours
The effects of mediators lasts only minutes to hours. How does long-standing inflammation occur?
Sustained production of mediators
Which chemical mediators are responsible for triggering vasodilation?
Where do these come from?
Vasoactive amines- histamine and serotonin (from mast cells and platelets)
Mediators derived from phospholipids-
Prostaglandins (from many cells)
Which chemical mediators are responsible for increased vascular permeability?
Vasoactive amines- Histamine and Serotonin (from mast cells and platelets)
Vasoactive peptides- Bradykinin (from the plasma precursor kininogen)
Mediators derived from phospholipids- Leukotrienes (from leucocytes)
Complement components- C3a, C4a and C5a (from complement plasma precursors).
Which chemical mediators are responsible for chemotaxis?
Mediators derives from phospholipids- Leukotriene B4 (from leukocytes)
Complement components-C5a and C3a (from complement plasma precursors)
Chemokines (from leucocytes and other cells)
Exogenous mediators- Bacterial products (from bacterial metabolism)
Clotting and fibronolytic cascades- Thrombin and fibrin degradation products
Which chemical mediators are responsible for triggering phagocytosis?
Complement components- opsonin C3b (from complement plasma precursor
Which chemical mediators are responsible for producing pain?
Vasoactive peptides- bradykinin (from the plasma precursor kininogen)
Mediators derived from phospholipids- Prostaglandins (from many cells)
Why are histamine and serotonin usually one of the first chemical mediators involved in inflammation?
Unlike many other mediators, histamine and serotonin are available immediately from preformed supplies and are already present within cells in the tissues and platelets at the site of injury when vessels are damaged.
Which cells is histamine released from?
mast cells, basophils and platelets (stored in granules in these cells)
Which cells is seratonin released from?
Platelets
How do aspirin and NSAIDs reduce pain and swelling?
They block the production of prostaglandins by inhibiting the enzyme cycle-oxygenate (the enzyme that produces prostaglandins from arachadonic acid)
How is bradykinin stored and releases?
Circulates in the blood as part of the larger molecule kininogen (produced in liver)
The enzyme kallikrein cleaves kininogen to produce bradykinin
How are complement components involved in killing microorganisms?
Complement components form a tube (membrane attack complex) which punches holes in bacteria causing them to die. When it assembles into its tube structure, it generates as by products, powerful inflammatory mediators:
What are cytokines and chemokines?
Give some examples.
Cytokines are polypeptides that are produced by many cells- act as messengers between them.
Chemokines are a group of cytokines involved in chemotaxis.
Eg. Interleukins, tumour necrosis factor (TNF), Interferons
They have local and systemic effects.
How do exogenous mediators of inflammation cause different effects in tissue and blood?
- when released into tissue—> inflammation
- when released into blood—> numerous inflammatory mechanisms at once resulting in septic shock
How does vascular flow change during acute inflammation?
- Transient vasoconstriction of arterioles.
- Vasodilation of arterioles.
- Increased permeability of blood vessels
- Exudation of fluid and concentration of red blood cells in small vessels leads to increased viscosity of blood = STASIS
How is exudate formed?
- The semipermeable membrane becomes leaky.
- The main force driving he fluid out of the vessels is increased-arterioles dilate increasing capillary pressure.
- The main force driving fluid back into the blood is reduced- plasma proteins escape into the tissue spaces raising the osmotic pressure there so that it roughly equals that of blood.
- Net flow of fluid out of vessel
What are the two types of oedema?
Transudate
Exudate
What is the difference between transudate and exudate?
Transudate-
Fluid loss due to hydrostatic pressure imbalance (low protein content)
Exudate-
Fluid loss in inflammation (protein rich)
What are the functions of exudate?
Delivery of nutrients, oxygen, cells and plasma proteins to the site of injury:
- inflammatory mediators: opsonise, complement
- antibodies
- fibrinogen
Excess fluid drains from tissues into the lymphatics taking with it microorganisms and antigens which are thus presented to the immune system
Which cell is the primary type of leucocyte involved in acute inflammation?
Neutrophils
How do neutrophils migrate to the site of injury?
Chemotaxis, diapedesis, emigration
What is chemotaxis?
Movement along concentration gradients of chemoattractants
Give some examples of chemotaxins.
Activation of complement releases C3a C4a C5a Bacterial peptides eg. Endotoxins Injured tissues Substances produced by leucocytes Thrombin and fibrin degradation products
How do neutrophils work?
- Chemotaxis
- Activation
- Margination
- Rolling
- Adhesion
- Emigration and diapedesis
- Phagocytosis
How are neutrophils activated?
- Ca2+ and Na+ enter the cell
- Cell swells
- Rearrangement of cytoskeleton assuming a roughly triangular shape pointing in the direction of the chemotactic stimulus
- Production and release of pseudopodia
- Activated cell is sticky
How is the way that exudate escapes blood vessels different to the way leucocytes leave blood vessels?
Exudate escapes via the gaps in the endothelial lining of the blood vessel
Leucocytes dig their way out of the blood vessel walls:
- relaxation of inter-endothelial cell junctions
- digestion of vascular basement membrane
- movement
What are opsonins?
Substances which make it easier for phagocytes to recognise targets, attach to pathegons making phagocytosis more effective. Eg. C3b
What are the mechanisms of killing by phagocytes?
-O2 dependent-oxygen burst /respiratory burst
Produces free radicals which are released into the phagosome
-O2 independent- using enzymes
Lysozyme, proteases, phospholipases, nucleases
Bactericidal permeability increasing protein (BPI)
How does inflammation present clinically?
Oedema
Exudation of fluid into tissues
Inflammation
Infiltration of inflammatory cells
What are the local complications of acute inflammation?
- damage to normal tissue
- swelling- obstruction of tubes, compression of vital structures eg. Bile duct and intestine
- exudate-compression eg. Cardiac tamponade
- loss of fluid-if fluid accumulates the tissue pressure increases until it reaches a level that prevents further exudation. However, fluid can continuously leak from a surface wound
- pain and loss of function
What are the systemic complications of acute inflammation?
Fever
Leucocytosis
Acute phase response
Shock
Why does acute inflammation cause fever?
Fever occurs when the thermostat of the body (situated in the anterior hypothalamus) is switched to a higher setting.
Macrophages when they are stimulated to do so by exogenous (bacterial) pyrogens (endotoxins) produce pyrogenic cytokines
Why is fever physiologically useful?
Some bacteria cannot survive at high temperatures (40-41degrees celsius)
Inflammation has been demonstrated to be more effective at higher temperatures
What is leucocytosis? What is the difference bacterial and viral infections?
The number of circulating leucocytes increases.
In bacterial infection, the number of neutrophils increases.
In viral infection, the number of lymphocytes increases;
What is the acute phase response?
Changes in the levels of some plasma proteins seen because the liver changes its patterns of protein synthesis. This occurs within hours of injury.
Albumin and other proteins are produced in smaller amounts.
Fibrinogen, ceruloplasmin, c3, alpha-1 antitrypsin, c-reactive protein are produced in greater amounts.
This causes:
- altered sleep patterns
- decreased appetite
- raised pulse rate
Explain the process of the resolution of acute inflammation.
– Exudate drains to lymphatics
– Fibrin is degraded by plasmin and other proteases
– Neutrophils die, break up and are carried away or are phagocytosed
– Damaged tissue might be able to regenerate. However, if regeneration cannot occur or damage is extensive, a fibrous scar forms.
– Note that if tissue architecture has been destroyed, complete resolution is not possible.
What causes the resolution of acute inflammation?
• All mediators of acute inflammation have short half- lives.
• May be inactivated by degradation, e.g. heparinase
• Inhibitors may bind e.g. various anti-proteases
• May be unstable e.g. some arachidonic acid derivatives
• May be diluted in the exudate, e.g. fibrin degradation products.
• Specific inhibitors of acute inflammatory changes – e.g. lipoxins, endothelin
What are the different types of exudate?
- Pus/abcess
- Haemorrhagic exudate
- Serous exudate
- Fibrinous exudate
What is haemorrhagic exudate?
A haemorrhagic exudate contains enough red blood cells to appear bloody to the naked eye. It indicates that as well as inflammation significant vascular damage has also occurred. It is seen in destructive infections or when the exudate is a result of infiltration by a malignant tumour.
What is serous exudate?
Serous exudates contain plasma proteins but few leucocytes suggesting that there is no infection by micro-organisms. They are clear and are seen typically in blisters, e.g., after a mild burn. Note serous exudates differ from transudates because they contain plasma proteins and they differ from plasma because they don’t contain fibrinogen. NB. A seroma is a tissue space filled with clear, sterile fluid that occurs as a post-operative complication.
What is a fibrinous exudate?
In a fibrinous exudate there is significant deposition of fibrin (i.e., a blood clot without the red blood cells). When fibrinous exudates occurs in the pericardial or pleural spaces the fibrin that is deposited means that the serosal surfaces no longer slide smoothly over each other. This results in friction between the serosal surfaces which can be heard as a rubbing sound.
What is an autopsy?
Post-mortem examination
What is a coroner’s autopsy?
Performed on behalf of HM coroner
No consent needed as it is a legal requirement
Why are coroner’s autopsies taken?
- deceased unknown
- deceased not seen by a doctor within 14 days of death- can avoid post mortem examination if a doctor signs death certificate
- attending doctor not able to give cause of death
- obviously unnatural death (murder, accident, suicide)
- death related to occupational disease/accident
- death related to medical treatment or procedure
- death of those who are in care of the state eg. Detained in hospital under mental health act, prisoners, young offenders
What is involved in an autopsy?
History-circumstances before death from hospital reports, medical records (often limited)
External examination-natural disease, injury, medical intervention (scars), imaging
Internal examination-all systems examined in most cases but limited sometimes
What techniques are used in addition to history taking, external examination and internal examination in autopsies?
Histology Toxicology Biochemistry Microbiology Genetics
Why do most biochemical tests not work in the dead?
Cells die so electrolyte levels are no longer maintained as this is an active process.
Bacteria use nutrients so glucose concentration can not be measured.
What can be tested using biochemistry in autopsies?
Diabetic/alchoholic ketoacidosis- ketone concentration in the blood stays the same after death
Renal failure- urea and creatinine concentration stay the same after death
Where do berry aneurysms particularly occur?
In the brain
Explain what happens in an extradural haemorrhage.
Usually trauma at side of head. Skull is thin here Running underneath is the middle meninges artery (with an anterior and posterior branch) Blood gradually leaks from artery Compression of brain as skull is rigid
What are common causes of infective endocarditis?
Abnormal heart valves
IV drug abuse
Where can blood enter the pericardial sac from?
From the aorta
From the heart
What is chronic inflammation?
Chronic response to injury with associated fibrosis
From the following signs of acute inflammation:
Redness, heat, swelling, pain
What persists in chronic inflammation?
Redness and heat resolve but swelling and pain persist
What situations does chronic inflammation typically arise in?
After or alongside acute inflammation
Chronic persistent infections
Autoimmune conditions
Prolonged exposure to toxic agents
Which cells are predominantly involved in chronic inflammation?
Mononuclear cells- macrophages and lymphocytes
What is chronic inflammation?
Chronic inflammation is a response to injury with associated production of granulation tissue (fibrous tissue).
What is acute inflammation?
Acute inflammation is a stereotyped, immediate, transient response of vascularised living tissue to injury.
What may happen after the development of acute inflammation?
1) complete resolution
2) continued acute inflammation with chronic inflammation = abcess
3) chronic inflammation and fibrous repair possibly with tissue regeneration
4) death- due to shock
What causes lobar pneumonia?
Streptococcus pneumoniae
Describe the pathology of lobar pneumonia?
Streptococcus pneumonia in alveoli
Acute inflammation stimulates the formation of exudate which collects in the alveolar sacs
Results in inefficient gas exchange
Hypoxaemia and breathlessness
Describe the pathology of bacterial meningitis.
Acute inflammation in meninges.
Brain swells leading to compression as skull is rigid.
Inflammatory exudate damages blood vessels.
Vascular thrombosis and reduced cerebral perfusion.
What are common causes of a skin blister?
Heat
Sunlight
Chemicals
Why is the exudate formed in a skin blister clear?
Relatively few inflammatory cells.
Exudate is clear unless bacterial infection develops
Describe the pathology underlying an abcess.
Abscesses form in solid tissues. Inflammatory exudate forces tissues apart Liquefactive necrosis in centre May cause: High pressure---> pain Tissue damage Squashed adjacent structures
What are the consequences of acute inflammation in serous cavities?
Exudate pours into cavity
Localised fibrin deposition
Peritoneum—>ascites
Pleurae—> pleural effusion—> lungs cannot expand- respiratory impairment
Pericardium—>pericardial effusion—> cardiac tamponade- cardiac impairment
What occurs in chronic granulomatous disease?
Phagocytes are unable to generate the free radical superoxide.
Bacteria are phagocytised but the phagocytes cannot kill them as they can’t generate an oxygen burst.
What is the role of alpha 1 antitrypsin in acute inflammation?
A protease inhibitor which deactivates enzymes released from neutrophils at the site of inflammation.
Why do patients with alpha 1 antitrypsin deficiency develop lung disease?
Liver disease occurs as the hepatocytes produce an abnormal version of the protein which is incorrectly folded.
It polymerises and cannot be exported from the endoplasmic reticulum.
This causes hepatocyte damage and eventually cirrhosis.
What is angiotensin-oedema?
Rapid oedema of the dermis, subcutaneous tissue, mucosa and submucosal tissues
Why can inherited deficiency of C1-esterase inhibitor (a component of the complement system) cause oedema?
DONT KNOW
In a pleural effusion, exudate was found.
What does this show?
Acute inflammation in the pleural cavity
Give some differences between acute inflammation and chronic inflammation. (6)
Acute inflammation = stereotyped
Chronic inflammation = modulated, heterogenous
Main mechanism acute inflammation = vascular changes
Main mechanism chronic inflammation = fibrosis
Acute inflammation = redness, heat, swelling, pain
Chronic inflammation = swelling, pain
Acute inflammation = predominantly neutrophils
Chronic inflammation = predominantly macrophages
Acute inflammation = immediate response
Chronic inflammation = after a few hours
Acute inflammation—> resolution possible
Chronic inflammation—> repair and scarring
Acute inflammation = most of the time has no significant long term consequences
Chronic inflammation = long term consequences
When does chronic inflammation begin without any proceeding acute inflammation?
Chronic persistent infections eg. TB
Autoimmune conditions eg. Rheumatoid arthritis
Prolonged exposure to toxic agents eg. Silica
When does chronic inflammation arise after or alongside acute inflammation?
An ongoing bacterial infection
Is resolution possible following chronic inflammation?
NO
Repair and scarring
Can repair and scarring occur following acute inflammation?
NO
Resolution possible or
Death due to shock or
Repair and scarring by chronic inflammation
List some functions of macrophages.(6)
- Phagocytosis (particularly with difficult to kill bacteria eg. Myobacterium tuberculosis)
- Professional antigen presenting cells
- synthesis of cytokines, complement components, blood clotting factors, proteases
- stimulate angiogenesis important in wound healing
- induce fibrosis
- induce fever, acute phase response, cachexia
Which cell of the immune system would you see in a microscopic picture of a joint affected by rheumatoid arthritis?
Why?
Mainly plasma cells
This is an autoimmune disease in which antibodies are produced by plasma cells which attack articular cartilage at joints resulting in pain, joint stiffness and swelling.
Which cell of the immune system would you see in a microscopic picture of a tissue affected by Leishmaniasis (a protozoal infection)?
Why?
Mainly macrophages
Macrophages phagocytise protozoa ???? Idk im guessing
Which cell of the immune system would you see in a microscopic picture of gastric mucosa affected by chronic gastrititis?
Why?
Mainly lymphocytes but also plasma cells
Chronic gastritis is atrophy of the gastric mucosa resulting in the mucosa becoming thin and losing its function (no acid or enzymes produced)
This is a result of chronic inflammation and a cell-mediated response.
In what types of immune responses are eosinophils involved?
Allergic reactions, parasite infections, some tumours
How are fibroblasts and myofibroblasts attracted to a region of cell injury?
Respond to chemotactic stimuli
Recruited by macrophages
What do eosinophils look like?
Lobed nucleus
Pink cytoplasm
What do plasma cells look like?
Abundant golgi and cytoplasm visible
Mononucleate
What is a giant cell and when are they formed?
Multinucleate cells made by fusion of macrophages when phagocytosis cannot destroy an antigen
What are the different types of giant cell and how do they appear different to one another
1) Langhans giant cell
Nuclei arranges around the periphery of the giant cell
2) Foreign body giant cell
Nuclei arranged randomly in the cell
3) Touton giant cell
Nuclei arranged in a ring toward the centre of the cell
In a microscopic picture of a lung affected by tuberculosis, what would confirm diagnosis of tuberculosis?
Granuloma with caseous necrosis in the centre- appears as pink mush in centre
Langhans type giant cells - nuclei at periphery
What is the difference between where small foreign bodies and large foreign bodies are found in a foreign body giant cell?
Small- phagocytised by giant cell and can be seen within it
Large- giant cell sticks to its surface
When are Touton giant cells formed?
Lesions with high lipid content eg. Fat necrosis
What cells are often found alongside Touton giant cells?
These appear in lesions with high lipid contents eg. Fat necrosis
Therefore, Foam cells (macrophages whose cytoplasm appears foamy as they have phagocytised lipid) are also found here
Which type of giant cell would you find in a region of fat necrosis?
Touton giant cell
What are the possible complications of chronic inflammation? (4)
- Tissue destruction due to involvement in inappropriate immune responses.
- Excessive fibrosis
- Impaired function
- Atrophy
How can immune responses cause chronic inflammation?
When macrophages and lymphocytes meet with specific targets, mediators are released that cause inflammation.
The immune system uses inflammation as a non-specific mechanism to destroy its targets. The immune system does not always get it right and can attack inappropriate targets in certain diseases.
When does excessive fibrosis occur?
Chronic inflammation
Fibroblasts are stimulated by cytokines to produce excess collagen.
Why is fibrous tissue formed in chronic inflammation?
Production of collagen is initially helpful in chronic inflammation as it helps to wall off infected areas and the production of a fibrous scar to replace damaged tissue is essential in wound healing
Why does excessive fibrosis cause a problem?
Excess fibrous tissue/inappropriate fibrosis can replace normal parenchyma (functional tissue of an organ) tissue and impair the function of an organ eg. Interstitial fibrosis of the lung
If an area of fibrosis contains enough myofibroblasts, it can slowly contract and cause further problems. Eg. Contraction in a cirrhosis liver will impair the flow of portal blood resulting in ascites
Does chronic inflammation usually result in increased or decreased function. Give examples.
Usually decreased function eg. Chronic obstructive bowel disease
Rarely increased function e.g. mucus secretion, thyrotoxicosis
Describe the pathology of chronic cholecystitis.
Example of chronic inflammation leading to excessive fibrosis and acute inflammation occurring simultaneously with chronic inflammation.
- Repeated attacks of acute inflammation
- Repeated obstruction of cystic duct (liver to gall bladderor common bile duct (gall bladder to small intestine) by gall stones
- Muscle attempts to remove the stone (leaves and returns) causing mucosal damage
-Triggers repeated acute inflammation leads to chronic inflammation
-Fibrosis of gall bladder wall
What does the gall bladder usually look like?
Translucent tube
What consequences of chronic inflammation are shown in cirrhosis?
Excessive fibrosis leading to markedly impaired function
What are common causes of liver cirrhosis?
Mainly alcohol in UK
Fatty liver disease
Infection with HBV, HCV in other countries
Give an example of a disease where chronic inflammation leads to increased function.
Grave’s disease leading to thyrotoxicosis
Autoimmune disease
Antibodies for the TSH receptor are formed
Results in chronic inflammation
Thyroid produces and releases too much thyroxin
What is inflammatory bowel disease?
Family of idiopathic inflammatory diseases affecting the large and small bowel
Describe the pathology of inflammatory bowel disease.
-repeated attacks of acute inflammation and chronic inflammation simultaneously
-acute inflammation results in acute symptoms
-chronic inflammation influences long term pathology of the disease, this leads to:
Scarring, atrophy and reduces function of the bowel
What are the types of inflammatory bowel disease?
Ulcerative colitis
Crohn’s disease
A patient has superficial ulcers in the mucosa. They are experiencing diarrhoea and rectal bleeding.
Are they likely to have Crohn’s disease or ulcerative colitis?
Ulcerative colitis
A patient has transmural ulcers affecting the mucosa, submucosa, lamina propria and other tissues. They have strictures and fistulae.
Are they likely to have Crohn’s disease or ulcerative colitis?
Crohn’s disease
Give examples of how chronic atrophic gastritis causes decreased function.
1.Gastric mucosa is not replaced and is atrophic -becomes thin and does not produce enzymes or acid
2.Causes pernicious anaemia
Pernicious anemia is defined as a type of vitamin B12 deficiency that results from impaired uptake of vitamin B-12 due to the lack of a substance known as intrinsic factor (IF) produced by the stomach lining.
Describe the pathology underlying chronic atrophic gastritis.
Produces autoantibodies that destroy cells in the gastric mucosa
Chronic inflammation
Atrophy of gastric mucosa
This gastric mucosa is not replaced and is atrophic (becomes thin and does not produce enzymes or acid)- has a major effect on its function
What is a granuloma?
Group of macrophages and lymphocytes stuck together
Contains epithlioid cells- macrophages modified to look like epithelial cellls (elongated and tightly packed)
What is the difference between a giant cell and a granuloma
Giant cell = fused macrophages to create ONE multinucleate cell
Granuloma = group of macrophages AND lymphocytes stuck together (MORE THAN ONE CELL)
When are granulomas formed?
- Foreign bodies present
- Persistent low-grade antigenic stimulation
- Hypersensitivity/autoimmune
- Unknown causes
Why are granulomas formed?
A granuloma is the body’s way of dealing with particles that are poorly soluble or difficult to eliminate for some reason.
A granuloma forms around the particle, which can be free of phagocytise within the centre of the granuloma and walls it off whilst concentrating mononuclear cells within its centre with which it hopes to destroy the particle
What is the similarities and differences in appearance between foreign body granulomas and hypersensitivity/immune type granulomas?
Foreign body type- contain macrophages foreign body giant cells epithelioid cells some fibroblasts (at the periphery) few, if any, lymphocytes,
Hypersensitivity/immune type-
contain macrophages
giant cells (which may be of Langhans type)
Epithelioid cells (which are usually more prominent than in foreign body granulomas)
some fibroblasts (at the periphery)
lymphocytes
What type of granuloma is very similar in appearance to TB granulomas and why?
BCG granuloma
Caused by an organism which ellicits an immune response making you immune to TB
Therefore, it produces granulomas that are very similar to those seen in TB
