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
Where are sarcoidosis granulomas found?
Lymph nodes, lungs
How can you tell the difference between TB granulomas and sarcoid granulomas?
TB granulomas have caseous necrosis in the centre whereas sarcoidosis granulomas do not
Which inflammatory bowel disease causes granulomas to from?
Crohn’s disease
What is the difference between a granuloma and granulation tissue?
A granuloma is a group of macrophages and lymphocytes stuck together consisting of epithelioid macrophages. Often contain multinucleate giant cells.
Granulation tissue is formed in chronic inflammation and consists of fibroblast, myofibroblasts, chronic inflammatory cells and developing capillaries. Eventually turns into a scar.
During the healing process, when is the weakest point?
Around 10 days after healing
What is the difference between regeneration and hyperplasia?
Regeneration= proliferation of cells to replace lost structures and return to normal
Hyperplasia= excessive proliferation of cells so there are more cells than normal
Define haemostasis.
Haemostasis is the process of preventing or stopping bleeding in cases of trauma or disease while maintaining blood in its fluid state. Haemostasis is the stopping of haemorrhage.
Where does haemostasis occur?
Happens on a phospholipid surface where vessel integrity has been compromised
What is the aim of haemostasis?
Seal the hole until tissues are repaired.
Mechanisms are then in place to dissolve the clot once vessel integrity has been restored (fibrinolysis).
How can haemostasis be helped therapeutically?
- applying pressure to a bleeding point
- suturing of an injury
- application of a topical agent that aids clotting
What major steps are involved in haemostasis?
Primary haemostasis
1. Vasoconstriction - severed artery contracts, not enough to stop bleeding but enough to decrease the pressure downstream (contraction doesn’t occur in veins but the pressure in them is much lower)
- Primary haemostatic plug - temporary blockage of a break by an unstable platelet plug - this sticks to the injured vessel and connective tissue outside it. Fragile but may control bleeding. Forms in seconds to minutes
- Secondary haemostatic plug - blood coagulation or formulation of a fibrin clot which stabilises the friable platelet plug into a stable clot. This formed in approximately 30 mins.
How are platelets formed?
Bud off from the cytoplasm of megakaryocytes in the bone marrow
Why should patients who are on aspirin stop taking the medication for 7-10 days before surgery?
Aspirin inhibits cyclooxygenase - one of the enzymes responsible for the production of thromboxane A2.
Thromboxane A2 is a powerful platelet aggregator released by activated platelets, so aspirin prevents platelet aggregation and hence step 2 of haemostasis.
Platelets have a normal life span of 7-10 days so patients should stop taking the medication 7-10 days before surgery so that platelets are present that have not been affected by the drug.
What are the steps involved in forming a platelet plug?
- Platelet adhesion
Occurs when there is damage to the vessel wall and exposure of the underlying tissue - Platelet activation
Platelets are activated by many different substances in the blood. - Platelet aggregation
This is how the platelet plug (primary haemostatic plug) grows.
What are platelets activated by?
- collagen surfaces (within extravascular areas)
- ADP (released by activated platelets, injured red blood cells)
- thromboxane A2 (powerful platelet aggregator released by activated platelets)
- thrombin (informs platelets that clotting sequence is activated)
How does platelet adhesion occur?
Occurs when there is damage to the vessel wall and exposure of underlying tissue
Platelets stick to the exposed basement membrane specifically to VonWillebrands factor
What is the role of Von Willebrand factor?
- involved in platelet adhesion to the vessel wall
- involved in platelet aggregation
- stabilises factor VIII (8)
Where is Von Willebrand factor produced and released?
Platelets and endothelial cells
What is the role of the vessel wall in the control of clotting and haemostasis?
Vasoconstriction when an artery is damaged
Subendothelial layer traps platelets (Von willebrands factor)
Subendothelial layer performs a balancing act between opposing and avoiding clotting:
- produces vWF, exposure of collagen and tissue factor which initiates activation of clotting factors by the extrinsic pathway
- secretion of thrombomodulin (activates protein C) and plasminogen activator (fibrinolytic) that oppose clotting
What is the aim of the clotting cascade?
Amplification system activation of precursor proteins to generate thrombin.
Thrombin converts fibrinogen into insoluble fibrin.
This enmeshes the initial platelet plug to make a stable clot.
Where are clotting factors made?
Liver
Which vitamin is required for the synthesis of clotting factors?
Vitamin K
What is the difference between the intrinsic and extrinsic clotting pathways?
Intrinsic pathway
- involves all factors
- triggered by a negatively charged surface
- vessel does not need to be broken for it to occur
Extrinsic pathway
-triggered by a tissue factor present outside of the blood (thromboplastin)
Factor VII is involved in which pathway of the clotting cascade?
Extrinsic pathway
Tissue factor activates factor VII (7) which activates factor X (10)
What does PT measure?
PT = extrinsic pathway + common pathway
What does APTT measure?
Intrinsic pathway + common pathway
What are thrombophilias?
Inherited or acquired defects of haemostasis resulting in a predisposition to thrombosis eg. Deep vein thrombosis)
What stops clotting from continuing?
-dilution of clotting factors by blood flow
-natural anticoagulants that oppose the formation of fibrin. Main ones are:
Antithrombin III, protein C, protein S, nitric oxide, prostaglandins, heparin
-fibrin degradation products
Antithrombin III Protein C Protein S Nitric oxide Prostaglandins Heparin
Are all examples of…
Natural anticoagulants that oppose the formation of fibrin. If someone lacks any of these, they will experience repeated episodes of thrombosis.
What happens do a clot once it is formed?
Platelets in the clot die.
As they die, they cling to the fibrin and pull by their actin-myosin filaments in a mechanism same as muscle contraction
Clot retraction helps in pulling the sides of small wounds together and may toughen the clot by squeezing out fluid
How are clots broken down?
Fibrinolysis - dissolves the clot once vessel integrity is restored
- macrophages recognise the clot and break it down
- plasmin breaks down fibrin into fibrin degradation products
Where does plasmin come from?
Plasminogen (from liver) is cleaved by to form plasmin
Wha activates plasminogen to be converted to plasmin?
- tissue plasminogen activation (tPA)
- urokinase (found in urine)
- streptokinase (obtained from streptococci so not usually found in the body)
When are plasminogen activators used therapeutically?
Thrombi and thromboemboli break down
Why should streptokinase only be given to a patient once?
It is antigenic
Why is tissue plasminogen activator better than streptokinase for thrombus breakdown?
- higher affinity for fibrinogen than streptokinase
- not antigenic so can be given more than once
What are the side effects of plasminogen activators?
Bleeding commonly from gums or nose but more seriously can occasionally occur in the brain
What increases the activity of tissue plasminogen activator and ultimately sets the fibrinolytic system in motion?
The clotting cascade.
Fibrin increases the activity of tissue plasminogen activator which produce plasminogen which in turn breaks down fibrin to fibrin degradation products.
What are D-dimers an example of?
Fibrin degradation products
In what kind of conditions are there elevated fibrin degradation products in the blood?
Any conditions where there is thrombosis:
- disseminated intravascular coagulation
- deep vein thrombosis
- pulmonary embolism
Why are people who have just had surgery at increased risk of postoperative thrombosis?
Fibrinolytic activity drops and remains low for 7-10 days
What is the final fate of a clot?
The clot will eventually become organised (undergo fibrous repair) and be replaced initially by granulation tissue and then by a scar
What would you expect bleeding time, PTT and APTT to be in a patient with von willebrands disease?
Increased bleeding time (abnormal adhesion of platelets to vessel wall)
APTT prolonged (vWF stabilises factor VIII)
PTT normal
What is the inheritance pattern of Von willebrands disease?
Autosomal dominant
What are the common causes of thrombocytopenia due to decreased production of platelets?
- bone marrow infiltration by malignancy
- drugs (cytotoxic)
- infections eg. Measles HIV
- B12 and folate deficiency
What are the common causes of thrombocytopenia due to decreased platelet survival?
- immunological destruction eg. immune thrombocytopenia purpurin
- non-immunological destruction eg. DIC
How does an enlarged spleen cause thrombocytopenia?
Sequestration
How can massive blood transfusions cause thrombocytopenia?
Dilutional
Blood stored for >24 hours has no platelets
What would you expect bleeding time, PT and APTT to be in someone with thrombocytopenia?
Bleeding time prolonged
Normal PT
Normal APTT
What is petichae bleeding and when does it happen?
Pinpoint haemorrhages
Seen because of bleeding in capillaries typically due to vasculitis or abnormalities in the number of function of platelets
What would you find in a bone marrow biopsy from a patient with thrombocytopenia due to marrow failure?
Decreased megakaryocytes
What are happens in disseminated intravascular coagulation?
- an activator of clotting gets into the blood
- microthrombi are formed throughout the circulation
- process consumes platelets, fibrin and coagulation factors and activates fibrinolysis
- patient may then experience haemorrhage
What causes disseminated intravascular coagulation?
It is always a complication of another condition
- sepsis (especially gram negative sepsis as such bacteria produce endotoxins which activates clotting)
- severe trauma (eespecially to the brain as it contains large amounts of tissue factor (thromboplastin)
- extensive burns
- complications of childbirth
- malignancy
- snake bite
How is disseminated intravascular coagulation diagnosed?
Presentation: Microvascular thrombosis causes -gangrene of skin -renal failure -respiratory distress -GI ulceration Haemorrhagic componet causes -intracerebral bleeding -petechiae -haematuria -GI bleeding
Clinical investigations:
- raised FDP’s eg. D-dimers
- haemolytic anemia - RBC fragmented as they squeeze past thrombi
- raised APTT
- raised PT
- low fibrinogen
Patient has:
- haemolytic anaemia
- gangrene of skin
- renal failure
- petechia
- haematuria
- raised PT
- raised APTT
- low fibrinogen
- raised D dimers/FDPs
Diagnosis?
DIC
What is the inheritance pattern of haemophilia A?
X-linked recessive
What is haemophilia A?
Congenital lack in factor VIII (8)
Involved in intrinsic pathway
What would you expect PT, APTT and bleeding time to be in a patient with haemophilia A?
PT normal APTT prolonged (intrinsic pathway Bleeding time prolonged
How is DIC treated?
Treat underlying cause
If bleeding is a prominent feature:
Platelets, fresh frozen plasma (contains clotting factors), cyroprecipitates), RBC may be needed
Anticoagulants such as heparin may be required
What is the inheritance pattern for haemophilia B?
X-linked recessive
What would you except PT APTT and bleeding time to be in a patient with haemophilia B?
PT normal APTT prolonged (measures intrinsic pathway) Bleeding time prolonged
What happens in haemophilia B
Congenital lack of factor IX (9)
Involved in intrinsic pathway
What is the difference between anticoagulant and antiplatelet drugs?
Anticoagulant - disrupt clotting factors and hence the clotting cascade eg. Heparin, warfarin
Antiplatelet - prevent platelet plug formation eg. Aspirin
How does heparin work?
It is a co-factor for anti thrombin 3
Anti thrombin 3 inhibits factor II (prothrombin) and factor X of the clotting cascade disrupting the common pathway of the clotting cascade
APTT prolonged
Bleeding time prolonged
How does warfarin work?
Inhibits vitamin K
Vitamin K dependent clotting factors cannot work
Dosage is titrated to the patients PT test results, specifically INR results (INR is the ratio of the patients PT to a normal control)
How does aspirin work?
Inhibits cyclooxygenase pathway which produced thromboxane A2
Thromboxane A2 is produced and released by activated platelets and is a powerful platelet aggregator
Prevents platelet plug formation
Bleeding time prolonged
What type of blood vessels does atherosclerosis occur in?
Arteries
What is thrombosis?
The formation of a solid mass from the constituents of the blood within the circulatory system during life.
Is thrombosis the same as clotting?
No
What is the difference between thrombosis and haemostasis?
Haemostasis is the process of preventing or stopping bleeding in cases of trauma or disease while maintaining blood in its fluid state.
A thrombus is a solid mass formed from the constituents of the blood within the heart or vessels during life. Thrombosis is the process of formation of a thrombus. It occurs when normal haemostatic mechanisms are turned on inappropriately.
Where can thrombosis occur?
ANYWHERE in the circulatory system
Eg. Arteries, veins, heart
What factors predispose to thrombosis?
There are three fundamental predisposing factors to thrombosis. • Abnormalities of the flow of blood ◦ Stagnation ◦ Turbulence • Abnormalities of the blood vessel wall ◦ Atheroma ◦ Direct injury ◦ Inflammation • Abnormalities of the constituents of the blood ◦ Smokers ◦ Post-partum ◦ Post-op
Thrombosis can occur due to abnormalities of the blood vessel wall. What is a common cause of endothelium damage in the heart?
Myocardial infarction - damage to the area of endothelium overlying the infarct
How does endothelial damage predispose to thrombosis?
As in clotting, when there is endothelial damage, platelets adhere to exposed von Willebrand factor. When blood flow is swift, for example in arteries, the platelet thrombi generally don’t grow because the current washes away platelets, chemical mediators and clotting factors. However, if there is also stasis, a thrombus will form.
Why is slow or turbulent flow a predisposing factor for thrombosis?
Abnormal blood flow gives platelets a better chance to stick to the endothelium and clotting factors a chance to accumulate.
Turbulent flow can itself produce endothelial damage.
Why is thrombosis more frequent in veins?
They have slow flow and valves produce pockets of stagnant blood which gives platelets a better chance to stick to the endothelium and clotting factors a chance to accumulate.
Give some examples where blood flow in veins is slower than normal causing the affected individual to be predisposed to thrombosis.
- cardiac failure
- bed rest
- immobilised (lack of muscular contractions in the calves)
Why is pregnancy a predisposing factor for thrombosis?
Thee are increased levels of fibrinogen and factor VIII in the blood so it is hypercoaguable.
There is pressure on the large veins of the pelvis by the gravity uterus causing stasis of blood
Why is smoking a predisposing factor for thrombosis?
Activates factor XII (intrinsic pathway)
Why is the oral contraceptive pill a predisposing factor for thrombosis?
Causes hypercoagualability
How is a thrombus formed?
- platelets are the smallest formed elements in the blood so are more concentrated along the endothelium
- platelets are most likely to catch behind a valve
- here, other platelets aggregate and settle on the wall of the vessel particularly if
1. There is endothelial injury
2. Blood flow is slow - as in haemostasis, fibrinogen binds the platelets together and fibrin grows out of the platelet layer
- fibrin traps red blood cells, the surface of the red later is thrombogenic and platelets stick to the exposed fibrin
- a second layer of platelets forms and the process continues
What are lines of Zahn?
Are they more obvious in arterial or venous thrombi? Why?
• Lines of Zahn -Laminated structure (red layer is red blood cells, white layer is platelets)
these are more obvious in arterial thrombi as opposed to venous thrombi as blood flows over the surface of the forming thrombus in arteries
What is the difference in appearance of thrombi and post-morgen clots?
- Post-mortem clots form when blood is not flowing so are not laminated
- More rubbery and shiny and are not attached to the intima
When is the formation of thrombi associated with pain?
Thrombophlebitis refers to such painful superficial thrombi and have associated inflammation in the wall of the vein.
What is the difference between parietal and occlusive thrombi?
Parietal - attached to the wall of the vessel and restrict the lumen. Arterial thrombi tend to remain parietal.
Occlusive - fill and obstruct the lumen. When occlusive thrombi do form in an artery it tends to be over an atherosclerotic plaque that has cracked open. Such thrombi in coronary arteries can be fatal.
What is a thrombus on a cardiac valve called?
Vegetation. These easily embolise. They usually form on the valves of the left heart as they are exposed to greater pressures and therefore microtrauma which exposes the thrombogenic subendothelial tissue. They can become infected and this is particularly common in IV drug users.
Why does thrombosis occur in the heart and in arteries?
Likely to be due to abnormality of the vessel wall
Usually due to endothelial injury or turbulence eg. Atherosclerosis
Which arteries does thrombosis commonly occur in?
- coronary arteries
- carotid arteries
- abdominal aortic aneurysms
What do thrombin look like in arteries?
- Pale
- Granular
- Lines of Zahn - change colour as the constituents of blood change
- Lower cell content - than in veins
Why does thrombosis occur in veins?
More likely to be due to abnormality of blood flow, blood components
Usually where there is stasis
What do thrombi look like in veins?
- Soft
- Gelatinous
- Deep red
- Higher cell content
What are the outcomes of thrombosis?
- Resolution/lysis
- Propagation
- Organisation
- Recanalisation
- Embolism
What happens in resolution of a thrombus?
Complete dissolution of the thrombus by the fibrolytic system
Blood flow is re-established
Most likely when thrombi are small
What happens in propagation of a thrombus?
Progressive spread and enlargement of the thrombus in direction of blood flow.
Distally in arteries
Proximally in veins
There is stagnation of blood distal to the original thrombus causing new thrombi to form
What is organisation of a thrombus?
Reparative process
Ingrowth of fibroblasts and capillaries (similar to granulation tissue)
Haemorrhage, acute inflammation, chronic inflammation, wall of vessel replaced by fibrous tissue
Lumen remains obstructed
What is recanalisation of a thrombus?
Blood flow re-established but usually incompletely
One or more channels deformed through organising thrombus
How can a thrombus lead to embolism?
Part of the thrombus breaks off
Travels through the bloodstream
Lodges at a distant site
What are the effects of arterial thrombosis?
- Ischaemia
- Infarction (depends on site- if an end artery, this usually doesn’t happen if there is collateral blood supply to the affected area)
What are the effects of venous thrombosis?
- Congestion
- Oedema
- Ischaemia
- Infarction
In both arterial and venous thrombosis, there is a possibility of getting ischaemia and an infarction. How does the process in which this occurs differ in each?
Arterial:
Less blood supply to the region that the artery affected by a thrombus supplies
Lack of oxygen and glucose to this region
If an end artery, there is no collateral supply leading to necrosis and hence an infarct
Venous:
Thrombus blocking the vein causes pressure in the veins to increase, eventually causing fluid to leak out of the veins into the surrounding tissue
Tissue pressure eventually equals arterial pressure
Blood cannot flow to region a there is no hydrostatic pressure gradient
Why do women with inherited thrombophilias have repeated miscarriages?
Thrombosis of uteroplacental vasculature leading to ischaemia
What is an embolism?
Embolism is the blockage of a blood vessel by an embolus which is solid, liquid or gas at a site distant from its origin.
Why are thromboemboli found in arteries and not veins?
In veins, blood flow is from smaller to larger vessels. Objects carried by the blood in veins will therefore go through the right heart and embolise in the pulmonary arteries.
In arteries, blood flow is from large to small arteries so objects carried by the blood in large arteries will become impacted into smaller arteries. Therefore, emboli from the left heart or aorta can end up anywhere in the systemic circulation but especially in the lower limbs.
A thrombus forms in a systemic vein. Where will it embolism?
Lungs (unless there is a CHD)
A thrombus forms in the left side of the heart. Where will it embolism?
Systemic arteries
Typically in the lower limbs
A thrombus forms in an atheromatous carotid artery. Where will it embolise?
Brain
A thrombus forms in an atheromatous abdominal aorta. Where will it embolise?
Arteries in the lower limb
List some predisposing factors for thrombosis.
- immobility/bed rest
- post operative
- pregnancy and post-partum
- oral contraceptives
- severe burns
- cardiac failure
- DIC
Where do pulmonary emboli arise from?
Approximately 80% from thrombi in deep veins of the thigh and popliteal vein
What are the effects of a pulmonary embolism?
- Small pulmonary emboli - small and clinically silent
- Multiple small pulmonary emboli - pulmonary hypertension
- Large pulmonary emboli - resulting in more than 60% occlusion of the pulmonary circulation can cause sudden death, right sided heart failure, cardiovascular collapse
- Large saddle emboli - become lodged at the bifurcation of the pulmonary arteries and result in sudden death
Where do thromboemboli in systemic arteries arise from?
Thromboemboli in systemic arteries arises from the left heart, aneurysms and thrombi on arteries with ulcerated atherosclerosis. They embolise to the lower extremities, brain, intestines, kidneys, spleen and arms.
Why might a thrombus form in the left side of the heart?
- Infarcts commonly affect the left ventricle. Thrombi can then form on the affected necrotic endothelium in the ventricular cavity. As the heart is beating these often embolise.
- Atrial fibrillation results in decreased atrial contraction, dilatation of the left atrium, stagnation of blood in the left atrium and hence thrombus formation
- Vegetations are commoner on valves of the left side of the heart because LHS is under higher pressure
What is a paradoxical embolism?
Thromboemboli that form in the systemic veins but embolise to the systemic arteries. They manage to bypass the lungs in one of two ways:
- Small emboli are able to pass through the arterio-venous anastomoses in the pulmonary circulation. Incidentally, this is also the way that fat droplets through the lungs in fat embolism.
- Larger emboli can only enter the systemic circulation by passing through defects in the interventricular septum or a patent foramen ovale during coughing, lighting or straining (increases pressure in the right side of the heart to greater than that in the left, pushing the thrombus through the defect).
What should be considered when a young patient presents with an ischaemic stroke?
Patients with a stroke are four times more likely to have a patent foramen ovale when compared with the general population so a paradoxical embolus.
How do atheromatous emboli form?
Atheroma is the gruel-like necrotic material present in atherosclerotic plaques. It can be released into the blood when a plaque breaks open. This can happen spontaneously and also during surgery or catheterisation for coronary artery disease. Such emboli often affect the intestine and present with abdominal pain.
What are transient ischaemic attacks (TIAs)?
Episodes of neurological dysfunction that appear suddenly, last minutes to hours and then disappear. They are the result of microscopic emboli, usually atheroemboli to the brain. The atheroembolus usually comes from the carotid arteries. Sometimes the are the result of thromboemboli that arise in the left heart. As the emboli are very small they break up quickly before any lasting damage is done so neurological symptoms dissappear after a short time.
How do fat and bone marrow emboli form?
- Complication of bone fractures - when bone is fractured the bone marrow fat cells that are injured break up and release oil droplets. These come together over a period of a few days and are then sucked into gaping venules that have been torn by the fracture. Symptoms of fat embolism (respiratory distress and neurological symptoms) are therefore seen 1-3 days after the fracture.
- Fat emboli can occur after liposuction
What are the symptoms of fat and bone marrow emboli?
• Respiratory symptoms - result of emboli that lodge in the lungs
• Some droplets pass through the lungs in a similar way to small thromboemboli to organs such as the brain, kidneys and skin where they cause:
◦ Agitation
◦ Coma
◦ Renal failure
◦ Petechial rash
How can trauma of the neck and chest cause air embolism?
There is negative pressure in the veins of the chest and head during inspiration in the upright position. These veins can draw in air after trauma here. The fatal amount of air is approximately 100mls. The air is transported to the right heart where bubbles gather as a frothy mass that stops the circulation.
How can labour cause air embolism?
Air can enter the uterus and be forced into open veins during uterine contraction
How does amniotic fluid embolism occur?
- Complication of labour and caesarean section
* Amniotic fluid enters the maternal circulation through a tear in the amniotic membranes.
What type of emboli are found in IV drug users?
Talcum emboli - microscopic foreign bodies with which drugs have been cut are found in the lungs of intravenous drug abusers.
These can produce a marked foreign body reaction and pulmonary symptoms.
What precautions are taken to prevent venous stasis and reduce the risk of thromboembolic disease after surgery?
- Mobilise early after an operation or illness
- During and after an operation legs can be elevated and measures to increase venous return such as compression stockings, calf muscle stimulation, passive calf muscle exercises can be employed
How can hypercoaguability be prevented to reduce the risk of thromboembolic disease?
Anticoagulants:
- aspirin
- heparin
- warfarin
How can filters be used in the prevention of thromboembolic disease?
pulmonary emboli can be prevented by putting an umbrella shaped filter in the inferior vena cava.
What is INR?
Ratio of the patients PT to a normal control
What is arteriosclerosis?
Hardening of the arteries. In this condition the walls of the arteries are thickened and lose their elasticity. It includes three diseases: atherosclerosis, arteriolosclerosis, monkeberg’s disease
What is arteriolosclerosis?
The thickening of the walls of arteries and arterioles. The disease affects arterioles throughout the body especially those of the kidney. It has little or no connection with atherosclerosis and usually occurs as a result of hypertension or diabetes mellitus
What is atherosclerosis?
Atherosclerosis is the accumulation of intracellular and extracellular lipid in the intima and media of large and medium sized arteries. Plaques form filled with atheroma and these often calcify.
What does an atheroma consist of?
It is the necrotic core of the atherosclerotic plaque consisting of dead cells, debris and cholesterol crystals.
What is Monkeberg’s disease?
Uncommon disease where there is calcification of the media of large arteries
What are the components of an atherosclerotic plaque?
- Cells - macrophages, leucocytes, smooth muscle cells
- Intracellular and extracellular lipid
- Extracellular matrix
Describe the cellular events leading to the formation of an atherosclerotic plaque.
- Chronic endothelial insult from conditions such as hyperlipidaemia, hypertension, smoking or from haemodynamic factors result in endothelial dysfunction.
- Lipid droplets, mainly from low density lipoproteins and monocytes cross the endothelium and accumulate in the intima. The lipids become oxidised and the macrophages ingest the lipid. When they do so their cytoplasm appears bubbly microscopically and they are called foam cells.
- The crowded foam cells cause the endothelium to bulge. Smooth muscle cells migrate into the lesion from the media and start to proliferate. The lesion at this stage is called a fatty streak.
- The plaque grows as the number of foam cells and smooth muscle cells increase. Some smooth muscle cells take up the lipid and appear foamy. Some smooth muscle cells lie over the plaque but beneath the endothelium forming a ‘roof’. This roof is reinforced by collagen, elastin and other matrix proteins and the result is a fibrous cap. As the endothelium stretches over the plaque, gaps appear between the endothelial cells. Platelets adhere to the gaps.
- Cells in the centre of the plaque die and necrosis develops. The dead cells release cholesterol and cholesterol crystals appear in the plaque (these are removed during tissue processing for microscopy leaving behind linear holes in the tissue section = cholesterol clefts. Small blood vessels from into the plaque from the adventitia and the plaque may undergo calcification.
What re fatty streaks?
Lipid deposits in intima. Thought to predispose to atherosclerosis but there is some debate about this as many fatty streaks do not develop into atherosclerosis.
An atherosclerotic plaque can become a complicated plaque due to ulceration. What happens?
The fibrous cap is eroded from underneath and the core of the plaque is exposed to the blood. This core is highly thrombogenic.
How can an atherosclerotic plaque result in aneurysm formation?
A local dilatation may result when elastic tissue within the arterial wall is destroyed by the plaque. This weakens the wall and may result in rupture of the vessel.
Describe the microscopic appearance of a fatty streak.
- accumulation of foam cells
- proliferation of smooth muscle cells
- extracellular lipid deposition
Describe the microscopic appearance of an atherosclerotic plaque.
- fibrosis
- necrosis
- cholesterol clefts
- increase in inflammatory cells
- disruption of internal elastic lamina
- extension into media
- ingrowth of blood vessels
- plaque fissuring
Wha is an aneurysm?
Local dilatation of an artery due to weakening of the arterial wall. In large arteries they are almost always secondary to atherosclerosis. Like atherosclerosis, they are a disease of arteries. Dilatations in veins are called varicies.
What are the types of aneurysm?
• Saccular aneurysm ◦ Shaped like a sac ◦ Lined or filled with thrombus which may be advantageous as it can protect the thrombus from bursting • Fusiform aneurysm ◦ Shaped like a spindle
What are the complications of an abdominal aortic aneurysm?
• Dissecting aneurysm
◦ Only occurs in the aorta and its major branches
◦ Form within a couple of minutes
◦ Inner layer of arterial wall tears open, blood enters and separates media into 2 layers, tear fills with blood and the lumen of the artery can be occluded. Second tear can push blood back into lumen
• Ruptured aneurysm
◦ Leads to retroperitoneal haemorrhage
What are the complications of cerebral ischaemia?
• Transient ischaemic attack (mini stroke)
◦ Presentation? Similar to stroke eg. Face drop, neurological impairment but these resolve in 24 hours
• Cerebral infarction (stroke)
◦ Presentation? Ipsilateral neurological problems, does not resolve within 24 hours
• Multi-infarct dementia
◦ Lots of small cerebral infarcts that on their own do not present clinical symptoms
What are the complications of peripheral vascular disease?
• Intermittent claudication
◦ Presentation? Pain in calves on walking, pain will resolve if you stop and rest, pain will reoccur after a short distance (claudication distance- decreases if you stop and rest for longer)
• Leriche syndrome
◦ Presentation? Pain in the buttocks, may be associated with impotence
• Ischaemic rest pain
◦ Not enough blood supply to the peripheries to maintain them in resting state
• Gangrene
◦ Not able to maintain tissues at all
How are conditions that affect the heart, brain, kidneys, legs or bowel caused by atherosclerosis?
narrowing/blockage of vessels or embolism of plaque material or thrombus that has formed on a plaque.
What determines the size of a cell population?
- cell proliferation
- cell differentiation
- cell death by apoptosis
How is cell proliferation controlled?
Chemical signals from micro-environment
Signalling molecule binds to a receptor which results in modulation of gene expression. Receptors are usually in the cell membrane but can be in the cytoplasm or nucleus (steroid receptors)
Proto-oncogenes regulate normal cell proliferation
How does a cell become permanent (quiescent). Where does it exit the cell cycle?
When a cell receives an instruction to divide, the cell enters the cell cycle (G1—>S—>G2—>M). After cell cycle completion, the cell either re-starts the process from G1 or exits (G0) until further growth signals occur. Cells in G0 can undergo terminal differentiation where there is a permanent exit from the cell cycle.
Can you see the cell cycle by microscopy?
You can’t see interphase (G1, S, G2) by light or electron microscopy
Mitosis (nuclear division) and cytokinesis (cell division) can be seen under a light and electron microscope
What changes occur in the cell cycle for a cell population to increase its numbers?
Increased growth occurs by:
- shortening the cell cycle
- conversion of quiescent cells (in G0) to proliferating cells (to G1) by making them enter the cell cycle
Why is number of cells in mitosis at a certain time counted in tumour biopsies?
Indicates what grade of cancer it is
What prevents cells with damaged DNA from replicating?
No. There are checkpoints in the cell cycle to check whether:
• there is damage to the DNA
• all of the DNA has been replicated.
If there is damage to the DNA:
• DNA repair mechanisms aim to fix the DNA
• Apoptosis triggered if DNA cannot be repaired
What are the checkpoints in the cell cycle?
- Restriction point at end of G1–> activates p53 protein for DNA repair/apoptosis
- G1/S transition —> checks for DNA damage before DNA replication
- G2/S transition —> checks for DNA damage after DNA replication
What is the most critical checkpoint in the cell cycle and why?
Restriction (R) point - checkpoint activation activates p53 protein which:
• delays cell cycle
• triggers
◦ DNA repair mechanisms OR
◦ apoptosis
When?
After G1
Why is it important?
• Majority of cells that pass R point will complete the cell cycle
• It is the most commonly altered checkpoint in cancer cells
How is the cell cycle controlled?
- Cyclins (proteins) that bind to and activate…
- Cyclin dependent kinases (CDKs) that phosphorylate…
- Target proteins that are critical for progression of the cell to the next stage of the cell cycle (eg. Retinoblastoma susceptibility protein)
How can cyclin dependent kinases be used to slow down the cell cycle?
Inhibitors of CDK tightly regulate cyclin-CDK complexes and concentration or structure of these may change in cancer
How do growth factors work?
- stimulate the production of cyclin
- decrease the production of CDK inhibitors
How many times can a cell divide?
• As a cell divides, its’ telomeres get shorter and shorter until coding DNA is lost
• Therefore, the telomerase enzyme determines how many times a cell can divide as this adds telomeres and hence lengthens the chromosome.
Hayflick limits demonstrate the maximum number of times a cell can divide. Humans have an average Hayflick number of 61.3.
What does regeneration mean?
Replacement of cell losses by identical cells in order to maintain the size of a tissue or organ.
Is regeneration always a normal process?
No.
It can be a normal process eg. The replacement of red and white blood cells by bone marrow
But it can also occur after injury if the harmful agent is removed and if there is limited tissue damage. However, if the harmful agent persists, if there is extensive tissue damage or if the damage occurs to a permanent tissue, then regeneration and resolution is not possible and instead the tissue will heal with a scar.
How are cells induce to regenerate?
- growth factors in the micro environment
- cell to cell communication
Which tissues can undergo regeneration?
Stable or labile tissues
What is the regenerative capacity of bone like?
Very good
What is the regenerative capacity of tendons like?
Poor
Heal very slowly as they have few cells and few blood vessels. Therefore, secondary rupture at a site of previous injury is not uncommon.
What is the regenerative capacity of articular cartilage like?
Poor - avascular
What is the regenerative capacity of adipocytes like?
There is no regeneration.
New fat cells are formed by undifferentiated but committed cells that lie among the adipocytes
What is the regenerative capacity of epithelia like?
Very good
Exceptions: lens of eye and renal podocytes
What is the regeneration of melanocytes like?
Too little/too much
Scars in pigmented skin are usually pale
What is the regeneration of cell in the CNS like?
None.
Lost neurones cannot be replaced- they cease to multiply before birth. Severed CNS axons do not grow back effectively
What is regeneration of peripheral nerves like?
Regenerate in a predictable way
How can cells adapt to demands?
Hyperplasia - cells increase in number above normal
Hypertrophy - cells increase in size
Atrophy - cells become smaller and/or decrease in number
Metaplasia - cells are replaced by cells of a different type
Are cellular adaptations (hyperplasia, hypertrophy, atrophy, metaplasia) reversible?
Yes
Atrophy is the least reversible
What is hyperplasia?
Increase in tissue or organ size due to increased cell numbers
Which tissues can undergo hyperplasia?
Labile or stable tissues
Why would a group of cells undergo hyperplasia?
- increased functional demand
- hormonal stimulation or growth factor stimulation
What is the difference between hyperplasia and neoplasia?
- hyperplasia remains under physiological control and is reversible unlike neoplasia
- hyperplasia can occur secondary to a pathological cause but the proliferation itself is a normal response whereas in neoplasia the proliferation itself is abnormal
How can hyperplasia lead to neoplasia?
Repeated cell divisions exposes the cell to the risk of mutations and neoplasia
Give some physiological examples of hyperplasia.
- proliferative endometrium under influence of oestrogen
- bone marrow produces erythrocytes in response to hypoxia (erythropoietin production by the kidneys increases in response to hypoxia as it is detected by interstitial peritubular cells in the kidney)
Give some pathological examples of hyperplasia.
- eczema - hyperplasia of epidermis
- thyroid goitre in iodine deficiency. Reduced thyroxine levels lead to increased TSH. This leads to generalised thyroid enlargement as it has trophic effects on the thyroid gland that result in increased vascularity, increased size, increased number of follicle cells as well as stimulating all aspects of the synthesis and secretion of T3 and T4
What does hypertrophy mean?
Increase in tissue or organ size due to increased cell size. The cells contain more structural components so the workload is shared by a greater mass of cellular components.
Which tissues undergo hypertrophy?
Labile, stable but especially permanent tissues as they cannot replicate
In labile and stable tissues, hypertrophy usually occurs along with hyperplasia.
Why would a group of cells undergo hypertrophy?
(Like hyperplasia)
• Increased functional demand
• Hormonal stimulation
when the stimulus for hypertrophy and hyperplasia disappears, the cells and organs become normal size once again.
Give some physiological examples of hypertrophy.
Skeletal muscle
Pregnant uterus (hypertrophy and hyperplasia)
Give some pathological examples of hypertrophy.
Heart
When the heart is under increased demand to pump blood due to increased preload (pulmonary or systemic hypertension) or afterload (valvular disease), the cardiac muscle hypertrophies as this is a permanent tissue. Normal heart weights 300g. Hypertrophied heart up to 1kg.
Prostate gland
If there is enlargement of the prostate gland (by hypertrophy and hyperplasia), then the smooth muscle of the bladder pushes against an increased resistance to pass out urine so there is hypertrophy and hyperplasia of the smooth muscle.
Bowel
If there is a stricture of the bowel, the piece of bowel proximal to the stricture hypertrophies to push material through this restricted area.
If hypertrophy occurs in heart muscle when it is under increased demand, don’t athletes get cardiac muscle hypertrophy?
Athletes get hypertrophy of the heart but not to the extent of pathological hypertrophy.
Athletes rest after exercise, so the heart is not constantly under increased demand but with pathology eg. systemic hypertension, the heart does not rest.
Cardiac muscle hypertrophy is damaging because the heart cannot grow enough coronary arteries to supply all of the hypertrophied heart muscle. Therefore, some of the heart muscle dies and bands of fibrosis form between the cardiac muscle and bits of muscle are always hypoxic and there can be disruption of the electrical activity of the heart.
Since the heart does not work strenuously for a long period of time, the hypertrophic effects are short term and rather than long term and constant as is the case with pathological hypertrophy of the heart.
When does compensatory hypertrophy occur?
When there is damage to one of the prime organs. When you have damage to one kidney, the other kidney enlarges. Usually hypertrophy and hyperplasia occurs.
What is atrophy?
Shrinkage of a tissue or organ due to an acquired decrease in size or number of cells.
(If a cell atrophies- it gets smaller)
(If an organ or tissue atrophies- cells get smaller and number of cells decrease)
What happens in cellular atrophy?
- Shrinkage in the size of the cell to a size at which survival is still possible.
- Reduced structural components of the cell disposed of in auto phagosomes
- May eventually result in cell death
Is atrophy reversible?
Atrophy is reversible up to a point but after years or months it is less so particularly when parenchyma cells are replaced by connective tissue
Give some physiological examples of atrophy.
Ovarian atrophy in post menopausal women
What are the different types of atrophy?
• Reduced functional demand/workload = atrophy of disuse
muscle atrophy after disuse, reversible with activity
• Loss of innervation = denervation atrophy
wasted hand muscles after median nerve damage
• Inadequate blood supply (this happens when it is gradual, if sudden then there will be an infarct)
thinning of skin on legs with peripheral vascular disease
• Inadequate nutrition
wasting of muscles with malnutrition, brain is last to atrophy
Give some pathological examples of atrophy?
• Loss of endocrine stimuli
occurs in the breast and reproductive organs with withdrawal of hormonal stimulation, wasting of the adrenal gland with loss of pituitary ACTH following hypophysectomy.
• Persistent injury
polymyositis (inflammation of muscle)
• Ageing = senile atrophy
Why? Cells can no longer divide due to Hayflick number+ DNA is damaged due to lots of cell division
brain or heart
• Pressure
tissues around an enlarging benign tumour (secondary to ischaemia)
What is atrophy of extracellular matrix of bone caused by?
Biggest stimulus of bone production is pressure and movement so immobility will decrease bone matrix
What is metaplasia?
Reversible change of one differentiated cell type to another.
Why does metaplasia occur?
Altered stem cell differentiation
Represents adaptive substitution of cells that are sensitive to stress by cell types better able to withstand the adverse environment
Involves expression of a new genetic programme
What is the difference between metaplasia and dysplasia/cancer?
Metaplastic cells are fully differentiated and the process is reversible whereas in dysplasia and cancer the process is irreversible. Metaplastic epithelium is fully differentiated whereas dysplastic tissue is disorganised and abnormally differentiated.
What is the link between metaplasia and dysplasia?
Metaplasia is sometimes a prelude to dysplasia and cancer.
Does metaplasia occur across germ layers?
No.
Epithelium changes to epithelium
Mesenchyme changes to mesenchyme
Which cell types does metaplasia occur in?
Labile or stable cell types
Where does cigarette smoke cause metaplasia?
Bronchial pseudostratified ciliated epithelium
—>
Stratified squamous epithelium
What is Barret’s oesophagus?
Stratified squamous epithelium in the oesophagus changed to gastric glandular epithelium with persistent acid reflux.
This can lead to oesophageal adenocarcinoma
When do splenic cells undergo metaplasia?
When bone marrow is damaged, splenic tissue undergoes metaplasia to bone marrow
What is traumatic myositis ossificans?
Metaplasia of fibroblasts to osteoblasts in muscle.
This forms bone. Metaplastic bone can develop unto skeletal muscle following trauma when fibroblasts within the muscle tissue undergo metaplastic change to osteoblasts. This is often seen in young people and usually after a premature return to activity before proper healing has occurs.
Where is the most common site for metaplasia?
- Epithelial metaplasia.
- Often columnar epithelium (fragile) undergoes metaplasia to become squamous epithelium (resistant).
- Epithelial metaplasia is common on surface linings because they are exposed to insults.
- The metaplastic epithelium may lose functions that the original epithelium performed eg. Mucus secretion is lost when columnar epithelium becomes squamous epithelium, metaplastic
What is aplasia?
Complete failure of a specific tissue or organ to develop- it is an embryonic developmental disorder
Eg. Thymic aplasia aplasia of kidney
Also used to describe an organ whose cells have ceased to proliferate. Eg. Aplasia of bone marrow in aplastic anaemia
What is hypoplasia?
Underdevelopment or incomplete development of tissue or organ at embryonic stage
Inadequate number of cells
In a spectrum with aplasia
Is hypoplasia the opposite of hyperplasia?
No - hypoplasia is a congenital condition whereas hyperplasia is not.
How is hypoplasia different to atrophy?
Hypoplasia is underdevelopment or incomplete development of a tissue or organ whereas atrophy occurs when existing parts waste away
What is involution?
Overlaps with atrophy. Normal programmed shrinkage of an organ.
Give some examples of involution.
- uterus after childbirth
- thymus in early life
What is reconstitution?
Replacement of a lost part of the body - doesn’t happen in humans, when a scar is formed it is hairless and stretched
What is atresia?
No origins eg. Congenital imperforation of an opening
Anus
Angina
Small bowel
What is dysplasia?
Abnormal maturation of cells within a tissue. Potentially reversible. Often pre-cancerous.
What is a neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed.
What is a malignant neoplasm?
An abnormal growth of cells that persists after the initial stimulus is removed and invades surrounding tissue with potential to spread to distant sites.
What is a tumour?
A tumour is any clinically detectable lump or swelling.
What is cancer?
Cancer is any malignant neoplasm (an abnormal growth of cells that persists after the initial stimulus is removed and invades surrounding tissue with potential to spread to distant sites)
What is a metastasis?
A malignant neoplasm that has spread from its original site to a new contiguous site (particular by blood vessels/lymphatics)
The original site is the primary site and the place to which it has spread is a secondary site.
What is the difference between dysplasia and a neoplasm?
Dysplasia is a pre-neoplastic alteration in which cells show disordered tissue organisation. It is not neoplastic because the change is reversible.
A neoplasm is an abnormal growth of cells that persists after the initial stimulus is removed. Neoplasia is irreversible.
Give an example of a non-neoplastic tumour
Abcess
Haematoma
Neooplastic tumours can be benign or malignant. What is the difference?
Benign neoplastic tumours are abnormal growths of cells that persist after the initial stimulus is removed. They are confined to their site of origin and do not produce metastases.
Malignant neoplastic tumours are abnormal growths of cells that persist after the initial stimulus is removed and invades surrounding tissue with potential to metastasise to distant sites. It is the massive tumour burden that is dangerous to the host.
How do benign and malignant neoplasms appear different to the naked eye?
Benign tumours grow in a confined local area so have a pushing outer margin. This is why they are rarely dangerous. They often have a fibrous tissue around them- removal is clean.
Malignant tumours have an irregular outer margin and shape and may show areas of necrosis and ulceration (if on a surface). It shows areas of necrosis because it is relatively ischaemic in places since the tumour cannot induce blood vessels in all places or is growing faster than angiogenesis can occur.
When can benign tumours be dangerous?
A benign tumour in specific places can have severe consequences due to pressure on surrounding tissues.
How do benign and malignant neoplasms appear under a microscope?
A benign neoplasm has cells that closely resemble the parent tissue - they are well differentiated.
Malignant neoplasms range from well to poorly differentiated. Cells with no resemblance to any tissue are called anaplastic.
If a tumour has cells that are well differentiated, is it definitely benign?
No.
Although benign tumours are well differentiated, malignant tumours range from well to poorly differentiated
What does the term grade mean in the context of neoplasms?
Clinicians use the term grade to indicate differentiation. High grade is poorly differentiated.
Grade is an important factor for prognosis in certain cancers.
What is the difference between carcinoma in situ and invasive carcinoma?
Carcinoma in situ - malignant epithelial tissue above basement membrane
Invasive carcinoma - malignant epithelial tissue beyond basement membrane
What causes neoplasia?
Accumulated mutations in somatic cells.
The mutations are caused by initiators, which are mutagenic agents, and promoters which cause cell proliferation.
In combination, initiators and promoters result in an expanded monoclonal population of mutant cells. Chemicals, infections and radiation are the main initiators but some of these agents can acts as promoters. In some neoplasms, mutations can be inherited rather than from an external mutagenic agent.
A neoplasm emerges from this monoclonal population through a process called progression, characterised by the accumulation of yet more mutations.
Are intrinsic causes of mutation or extrinsic causes of mutation more important for causing neoplasia?
It is thought external factors (mutagens) are more important
External initiators include chemicals, infections, radiation.
(Internal initiations are inherited mutated genes)
What does monoclonal mean?
A collection of cells is monoclonal if they all originated from a single founding cell.
Genetic alterations affect particular types of genes. These are proto-oncogenes and tumour suppressor genes. How can they be affected to favour neoplasm formation?
Proto-oncogenes become abnormally activated (when they are then called oncogenes)
Tumour suppressor genes which normally suppress neoplasm formation become inactivated.
How many alleles must be mutated to create an oncogene?
One allele
How many alleles have to be mutated to inactivate a tumour suppressor gene?
2
Benign tumours end in…
-oma
Epithelial malignant neoplasms end in…
-carcinoma
Stromal malignant neoplasms end in…
-sarcoma
What is leukaemia?
Malignant neoplasm of blood-forming cells arising in the bone marrow.
What are lymphomas?
Malignant neoplasms of lymphocytes mainly affecting lymph nodes.
What is myeloma?
Myeloma is a malignant neoplasm of plasma cells.
What are germ cell neoplasms?
Arise from pluripotent cells mainly in the testes or ovaries.
What are neuroendocrine tumours?
Arise from cells distributed throughout the body
Some neoplasms are called ‘-blastomas’. What are they?
They occur mainly in children and are formed from immature precursor cells.
What are the most lethal features of a neoplasm?
The ability of malignant cells to invade and spread to distant sites leads to a greatly increased tumour burden. Untreated, this results in vast numbers of ‘parasitic’ malignancies.
How do malignant neoplasms metastasise?
- Malignant neoplasm grows and invades at the primary site.
- It enters a transport system and lodges at a secondary site.
- It grows at the secondary site to form a new tumour (colonisation).
At all points the cells evade destruction by immune cells.
Why can’t small tumours metastasise?
Metastasis is inefficient so requires many cells.
Inefficiency tends to lie in:
- travelling through a vessel- most cancer is carcinoma, epithelial cells are not designed to travel through blood vessels so are damaged by the flow of blood and vessel wall
- growth at a secondary site - has to be enough cells there sufficient for growth
Invasion of a malignant neoplasm into surrounding tissue requires 3 important alterations. What are they?
- altered adhesion
- stromal proteolysis
- motility
Together, these three changes create a carcinoma cell phenotype that sometimes appears more like a mesenchymal cell than an epithelial cell, hence this is called epithelial to mesenchymal transition.
What is altered adhesion between malignant cells?
- reduction in E-cadherin expression. (E-cadherin is initially reduced so the cell can detach but is then increased so cells can join together in the blood vessel). Changes are dynamic.
- altered adhesion between malignant cells and stromal proteins involves integrin expression.
Why must malignant cells undergo stromal proteolysis for invasion?
The cells must degrade basement membrane and stroma to invade. This involves altered expression of proteases, notably matrix metalloproteinases (MMPs)
Malignant cells take advantage of nearby non-neoplastic cells, which together form a cancer niche. These normal cells (fibroblasts and inflammatory cells) provide some growth factors ad proteases.
Invasion of malignant neoplasms to surrounding tissues involves altered motility. What is this?
Changes in the actin cytoskeleton. Signalling through integrins is important occurs via small G protein members use as members of Rho family.
How are malignant neoplasms transported to distant sites?
- Blood vessels via capillaries and venules
- Lymphatic
- Fluid in body cavities (pleura, peritoneal, pericardial, brain ventricles) - transcoelomic spread
What are micrometastases and why do they form?
At a secondary site malignant cells must grow. This is called colonisation. Failed colonisation is considered to be the greatest barrier to successful formation of metastasis because many malignant cells lodge at secondary sites but these tiny cell clusters either die or fail to grow into clinically detectable tumours. Surviving microscopic deposits that fail to grow are called micrometastases. These are surviving micro deposits of malignant cells that have failed to colonise at secondary sites. This may be because of:
- immune attack
- reduced angiogenesis
- hostile secondary site
What is tumour dormancy?
An apparently disease-free person may harbour many micrometastases. These are surviving micro deposits of malignant cells that have failed to colonise at secondary sites. This may be because of:
- immune attack
- reduced angiogenesis
- hostile secondary site
What is the typical cause of a malignant neoplasm relapsing years after an apparent cure?
One or more micrometastases start to grow.
What determines the site of a secondary tumour?
(1) Regional drainage of blood, lymph or coelomic fluid. For lymphatic metastasis this is very predictably to draining lymph nodes. For transcoelomic spread this is predictably to other areas in the coelomic space or to adjacent organs. For blood-borne metastasis this is sometimes (but not always) to the next capillary bed that the cells encounter. Therefore lungs are a very common place for blood-borne metastasis- this is the first capillary bed after entering from the venous system into the heart. From GI tract, the next capillary bed is the liver
(2) The “seed and soil” phenomenon, which may explain the seemingly unpredictable distribution of blood-borne metastases, is due to interactions between malignant cells and the local tumour environment (i.e. the niche) at the secondary site
How do carcinomas usually spread?
Carcinomas typically spread first to draining lymph nodes and then to blood-borne distant sites. Common sites of blood borne metastasis are lung, bone, liver and brain. The neoplasms that most frequently spread to bone are breast, bronchus, kidney, thyroid and prostate.
How do sarcomas tend to spread?
Via the blood stream
Malignant tumours have ‘personalities’. What does this mean?
Some malignant neoplasms are more aggressive and metastasise very early in their course. Eg. Small cell bronchial carcinoma.
Others almost never metastasise eg. Basal cell carcinoma of the skin.
The likelihood of metastasis is related to the size of the primary neoplasm.
What are the local effects of neoplasms?
- direct invasion and destruction of normal tissue
- ulceration at a surface leading to bleeding
- compression of adjacent structures
- blocking tubes and orifices
What are the systemic effects of neoplasms?
Increased tumour burden with secreted factors such as cytokines results in:
- reduced appetite and weight loss (cachexia)
- malaise
- immunosuppression (can also be due to direct bone marrow destruction)
- thrombosis
Benign neoplasms of endocrine glands are well differentiated so typically produce hormones, e.g. a thyroid adenoma produces thyroxine. Malignant tumours sometimes also produce hormones; e.g. bronchial small cell carcinoma can produce ACTH or ADH while bronchial squamous cell carcinoma can produce a PTH-like hormone.
Miscellaneous systemic effects include neuropathies affecting the brain and peripheral nerves, skin problems such as pruritis and abnormal pigmentation, fever, finger clubbing and myositis. Many other signs and symptoms can also occur and the pathogenesis is poorly understood
Describe the insudation theory for the mechanism of atherogenesis.
- Endothelial injury
- Inflammation
- Increased permeability to lipid from plasma
Describe the reaction to injury hypothesis for atherogenesis.
atherosclerosis is a chronic inflammatory response of the arterial wall initiated by injury to the endothelium. Lesion progression is sustained by interaction between modified lipoproteins, macrophages, T lymphocytes and cells of the arterial wall.
Describe the encrustation hypothesis for atherogenesis.
plaques are formed by repeated thrombi overlying thrombi. The lipid core is derived from the thrombi.
Describe the monoclonal hypothesis for atherogenesis.
this hypothesis arose following the finding that some plaques are monoclonal or oligoclonal. This raised the question of whether plaques are benign neoplastic growths, perhaps induced by cholesterol or a virus. However as some areas of normal arteries are clonal this theory hasn’t gained widespread popularity.
What are the risk factors for atherosclerosis?
- hyperlipidaemia
- diabetes mellitus
- hypertension
- age
- gender
- familial predisposition
- cigarette smoking
- alcohol consumption
- infection
- lack of exercise
- obesity
How does hyperlipidaemia increase the risk of atherosclerosis?
High plasma cholesterol - high LDL (most significant), HDL (protective - removed cholesterol from atheromatous plaques and delivers it to the liver for excretion in bile)
Diabetes mellitus causes hypercholesterolaemia
What lipoproteins can be used as a risk factor for atherosclerosis?
Genetic variations in Apo E are associated with changes in LDL levels
Polymorphisms of the genes involved lead to at least 6 Apo E phenotypes
Polymorphisms can be used as risk markers for atherosclerosis
What is hyperlipidaemia an dhow is it linked to atherosclerosis?
• Genetically determined abnormalities of lipoproteins
• Leads to early development of atherosclerosis in teens/early 20’s
• Associated physical signs
◦ Arcus
◦ Tendon xanthomas
◦ Xanthelasma
How can atherosclerosis be prevented?
Decreasing total and LDL cholesterol and increasing HDL. This is probably the most important strategy and can generally be achieved with diet and lipid-lowering drugs. Dietary measures include a low fat and high fibre diet. Food high in soluble fibre reduces circulating lipid,
• Stopping smoking,
• Controlling hypertension,
• Controlling weight and regular exercise,
• Sensible alcohol intake. A moderate intake (1-2 units/day) appears protective. Excess alcohol produces secondary hyperlipidaemia,
• Treating diabetes mellitus,
• Anti-oxidants, such as vitamin E, may be protective.
What is a pathological fracture?
Fracture caused by trivial trauma due to a disease that has led to weakness of bone structure.
What is cachexia?
Weakness and wasting of the body due to severe chronic illness
What is cancer?
Any malignant neoplasm (an abnormal growth of cells that persists after the initial stimulus is removed and invades surrounding tissue with the potential to spread to distant sites)
What is anaplasia?
Growth of cells with no resemblance to any tissue.
What changes are seen in individual cells with worsening differentiation?
Hyperchromasia - increasing nuclear staining
More mitotic figures
Pleomorphism - increasing variation in size and shape of cells and nuclei
What is pleomorphism?
Increasing variation in size and shape of cells and nuclei seen with worsening differentiation
Name for a benign tumour of glandular epithelia?
Adenoma
Name a benign tumour of stratified squamous epithelia.
Squamous papilloma
What is leiomyoma?
A benign connective tissue neoplasm of smooth muscle
What is a benign and malignant neoplasm of fat called?
Benign - lipoma
Malignant - liposarcoma
What are benign and malignant neoplasms of glial cells called?
Benign - glioma
Malignant - malignant glioma
All lymphoid and haematopoietic neoplasms are regarded as malignant.
True or false
Trueeeee
What is a dermoid cyst?
Benign teratoma of the ovary
What is a well differentiated neuroendocrine carcinoma called?
Carcinoid tumours - various organs
Phaeochromocytoma - adrenal
Small cell carcinoma of bronchus
What cell type are blastomas derived from?
Immature precursor cells - mainly in children
What is epithelial-to-mesenchymal transition (EMT)?
Alterations are needed for carcinoma cells to invade a new site:
Altered adhesion
Altered proteolysis
Altered motility
These three changes create a carcinoma cell phenotype that sometimes appears more like a mesenchymal cell than an epithelial cell so this is called EMT.
List the most common sites of blood-borne metastases.
Lung - first capillary bed after returning to RHS of heart
Liver - first capillary bed from GI tract (hepatoportal system)
Brain
List the neoplasms which most frequently spread to bone.
Neoplasms that most frequently spread to bone: • Breast • Bronchus • Kidney • Thyroid • Prostate
Which malignant neoplasms commonly cause lytic and sclerotic lesions in bone?
Lytic regions - destroys bone (all cancers except prostate)
Sclerotic regions - abnormal bone produced (prostate)
How does metastasis to bone present?
Pathological fractures - minor trauma leads to fracture
What is colonisation?
Primary tumour (which has migrated) growing at a secondary site to form a new tumour
Altered adhesion between carcinoma cells involves…
Altered E-Cadherin expression
Altered adhesion between carcinoma cells and stromal proteins involves…
Changes in integrin expression
Small G proteins such as members of the Rho family are involved in…
Signalling through integrins
Altered motility for invasion of a primary tumour to occur
Matrix metalloproteinases are involved in…
Altered expression of proteinases for invasion of a primary tumour to occur
What forms a cancer niche?
Malignant cells take advantage of nearby non-neoplastic cells to form a cancer niche. These provide growth factors and proteases
(Inflammation provides these factors)
Benign tumours of glands are well differentiated so can often produce hormones.
Bronchial small cell carcinoma can produce…
ACTH or ADH
Benign tumours of glands are well differentiated so can often produce hormones.
Bronchial squamous cell carcinoma can produce…
PTH-like hormone
What is pruritis?
Excessive itching often seen with lymphomas
What are the intrinsic risk factors for cancer?
Age
Sex (hormones)
Heredity (genes)
What are the extrinsic risk factors for cancer?
Environment
Lifestyle - BMI, low fruit + veg intake, lack of physical activity, tobacco use, alcohol use
What are the intrinsic causes of cancer?
Inherited mutation
Chronic inflammation
What are the extrinsic causes of cancer?
Chemicals
Viruses
Radiation
There is a long delay between carcinogen exposure and malignant neoplasm onset.
True or false?
True
The risk of cancer depends on total carcinogen dosage.
True or false?
True - the dependence on dosage is why industrial carcinogens and tobacco smoke are especially important causes of cancer.
There is sometimes organ specificity for particular carcinogens.
True or false?
True
Eg. 2-napthylamine causes bladder carcinoma
Carcinogens are either ______ or _______ (or both- complete carcinogens)
Initiators - mutagens
Promoters - cause sustained proliferation
What are complete carcinogens?
Initiator + promoter
What are the types of chemical carcinogens?
- polycyclic aromatic hydrocarbons
- aromatic amines
- nitrosamines
- alkylating agents
- natural products
What are pro-carcinogens?
Converted to carcinogens by the cytochrome P450 enzymes in the liver
2-napthylamine is an example of what class of chemical carcinogen?
Which cancer is caused by this?
Aromatic amine
Bladder cancer
What types of radiation are carcinogenic and where does it come from?
Radiation is any type of energy travelling through space.
• Ultraviolet (UV) light - does not penetrate deeper than skin (MOST IMPORTANT - exposed daily to sunlight leading to increased skin cancer risk)
• Ionising radiation - strips electrons from atoms (MAIN EXPOSURE - radon which seeps from earth’s crust)
◦ X- rays
◦ Nuclear radiation from radioactive elements
‣ Alpha particles
‣ Beta particles
‣ Gamma rays
How does radiation act as a carcinogen?
Acts as an initiator (mutagen) • Directly - Damages DNA ◦ Altered bases ◦ Single strand breaks ◦ Double strand breaks • Indirectly - Generates free radicals
How does ionising radiation damage DNA?
Directly
• Damages DNA bases
• Single strand breaks
• Double strand breaks
How can infections act as carcinogens?
- Directly - affect genes that control cell growth
- Indirectly - cause chronic tissue injury where the resulting regeneration acts either as a promoter for any pre-existing mutations or else causes new mutations from DNA replication errors.
Why is Human Papilloma virus (HPV) carcinogenic?
• Expresses E6 and E7 proteins • These inhibit p53 and pRB protein function respectively ◦ p53 - activates apoptosis ◦ pRB - causes cell cycle to arrest • Increases risk of cervical carcinomas
Why are Hepatitis B and C viruses carcinogenic?
• Cause chronic liver cell injury and regeneration
◦ Resulting tissue either acts as a:
‣ Promoter - for any pre-existing mutations
‣ Initiator - causes new mutations to form
How is Helicobacter pylori carcinogenic?
• Causes gastric inflammation ◦ Resulting tissue either acts as a: ‣ Promoter ‣ Initiation • Increases risk of gastric carcinomas
How are parasitic flukes carcinogenic?
• Causes inflammation in bile ducts and bladder mucosa
◦ Resulting tissue either acts as a:
‣ Promoter
‣ Initiator
• Increases risk of cholangio- and bladder carcinomas
What are tumour suppressor genes and how may they change in neoplasia?
- Inhibit neoplastic growth
* Both alleles must be inactivated (two hits - one for each allele)
What are proto-oncogenes and how do they change in cancer?
- Oncogenes enhance neoplastic growth
- When abnormally activated, become proto-oncogenes
- Only one allele of each proto-oncogene needs to be activated
What are caretaker genes and how may they change in cancer?
Caretaker genes are a class of tumour suppressor genes
- Repair DNA and maintain genetic stability
- One or both alleles can be inactivated depending on the cancer syndrome
What is RAS and explain its role in cancer?
Oncogene
Mutated in approximately 1/3 of all malignant neoplasms
• Function: Encodes a small G protein that relays signals into the cell to push the cell past the restriction point
Mutation in only one allele required
• Mutated version: Mutant RAS encodes a protein that is active all the time, producing a constant signal to pass through the cell cycle’s restriction point
What is the role of c-myc?
Oncogene
Function: encodes transcription factors
What is the role of c-erbB-2 (HER-2)?
Function: encodes growth factor receptors
What is the role of BCL2?
Oncogene
Apoptosis regulator
List some important oncogenes.
RAS
C-myc
HER-2
BCL2
What is the role of retinoblastoma normally and in cancer?
• Function: Restricts cell proliferation by inhibiting passage through the restriction point
Both alleles must be inactivated
• Mutated version: Allows unrestrained passage through the restriction point
Describe the inheritance of Hereditary non-polyposis coon cancer syndrome (HNPCC).
Carcinoma?
Colon cancer
Inheritance?
Autosomal dominant
Mutation?
• First germ line mutation in caretaker gene - affects of of several DNA mismatch repair genes
• Second somatic mutation in tumour suppressor gene/oncogene
Describe the inheritance of familial breast cancer.
Mutation?
First germ line mutation in caretaker gene - affects BRCA1 or BRCA2 genes which are important for repairing double strand DNA breaks (these mutations do not have to be inherited- can be found in sporadic malignant neoplasms
What is the two hit hypothesis?
Explains differences between tumours occurring in families and those occurring in the general population caused by mutations in the retinoblastoma gene (can occur in other tumour suppressor genes)
• Familial cancers
◦ First hit - germline and affected all cells in the body
◦ Second hit - somatic mutation
• Sporadic
◦ First hit - somatic mutation
◦ Second hit - somatic mutation
What is xeroderma pigmentosum?
An example of an inherited cancer syndorome that has a germline mutation that causes malignant neoplasms indirectly by affecting DNA repair
Carcinoma?
Skin cancer at a very young age
Inheritance pattern?
• Autosomal recessive
Mutation
• First germ line mutation in caretaker gene - Germ line in one of 7 genes that affect DNA nucleotide excision repair
• Second somatic mutation in tumour suppressor gene/oncogene - Patients are very sensitive to UV damage and develop skin cancer at a very young age
What are the three stages of carcinogenesis?
Initiation
Promotion
Progression including the adenoma-carcinoma sequence
What is the adenoma-carcinoma sequence?
- Most malignant tumours require alterations affecting a combination of multiple tumour suppressor genes and proto-oncogenes
- Early adenomas, later adenomas, primary carcinomas and metastatic carcinomas have accumulating mutations over a time frame which is typically decades
- This steady accumulation of multiple mutations is called cancer progression. The exact number of mutations needed for a fully evolved malignant neoplasm is unknown but thought to be approximately ten or less
What are the hallmarks of cancer?
- self-sufficient growth signals
- resistance to anti-growth signals
- grow indefinitely
- induce new blood vessels
- resistance to apoptosis
- invade and produce metastases
One of the hallmark features of cancer is:
Self-sufficient growth signals
Give an example of a molecular alteration that causes this.
HER2 gene amplification (breast cancer)
One of the hallmark features of cancer is:
Resistance to anti-growth signals
Give an example of a molecular alteration that causes this.
CDKN2A gene deletion (cyclin dependant kinase inhibitor) - melanoma
One of the hallmark features of cancer is:
Grow indefinitely
Give an example of a molecular alteration that causes this.
Telomeres gene activation (most cancers)
One of the hallmark features of cancer is:
Induce new blood vessels
Give an example of a molecular alteration that causes this.
Activation of VEGF expression (many cancers)
One of the hallmark features of cancer is:
Resistance to apoptosis
Give an example of a molecular alteration that causes this.
BCL2 gene translocation (lymphoma)
One of the hallmark features of cancer is:
Invade and produce metastases
Give an example of a molecular alteration that causes this.
E-Cadherin mutation (gastric cancer)
What is genetic instability?
Result of a mutation in an oncogene, tumour suppressor gene or caretaker gene.
Accelerated mutation rate found in malignant neoplasms
The dye industry is related with what type of carcinogen and malignancy?
2-napthylamine (aromatic amine) used in dye industry
Causes bladder carcinoma
Why do you not need promotion with germ line mutations?
All cells have the germ line mutation
Why are germ line mutations that cause cancer often in tumour suppressor genes?
A mutation in a proto-oncogene in an embryo would result in the formation of an oncogene which causes neoplastic growth. If this was present in an embryo, embryogenesis would not proceed normally so the foetus would not be viable.
A mutation in two tumour-suppressor genes are required for neoplastic growth. If there is a germ-line mutation in one tumour-suppressor gene, it is likely that embryogenesis can proceed as normal and the foetus is viable.
What is replication senescence?
Cells can no longer divide because telomeres have shortened so coding DNA is now lost.
Why is immortalisation one of the Hallmark features of cancer?
There is wastage of cells:
- necrosis
- not every cancer cell has equal ability to divide due to terminal differentiation
What is oncogene senescence?
Recognition and destruction of a cell with a mutated oncogene
What metaplasia of the bronchus occurs with cigarette smoke?
Squamous metaplasia
Which cancers account for over half of all new cancers in UK?
A majority of these cancers are diagnosed in people aged over…
- Breast
- Lung
- Prostate
- Bowel
65 (small proportion in people up to age 24)
Which cancers are common in children younger than 14?
- Leukaemias
- Central nervous system tumours
- Lymphomas
Name 3 cancers that have relatively good survival rates.
- Testicular cancer
- Malignant melanoma
- Breast cancer
Name 3 cancers that have relatively poor survival rates.
- Pancreatic cancer
- Lung cancer - biggest cause of cancer related deaths in UK
- Oesophageal cancer
What factors are considered when determining which individuals will have a favourable outcome for malignant neoplasms?
- Age
- General health status
- Tumour site
- Tumour type
- Grade (differentiation)
- Tumour stage
What is tumour stage and what is its significance?
Measure of the malignant neoplasms overall burden.
It is a powerful predictor of survival.
What is TNM staging?
Commonest, standardised method for assessing the extent of a tumour
Is a powerful predictor of survival
• T - refers to size of primary tumour
◦ T1/T2 = small primary, T2/T3 = large primary
• N - extent of regional node metastasis
◦ N0 to N3
• M - extent of distant metastatic spread
◦ M0 or M1
What is stage I in terms of T, N and M?
T1 or T2
N0
M0
Early local disease
What is stage II in terms of T, N and M?
T3 or T4
N0
M0
Advanced local disease
What is stage III in terms of T, N and M?
Any T
N1 or more
M0
Regional metastasis via lymphatics
What is stage IV in terms of T, N and M?
Any T
Any N
M1
Advanced disease with distant metastasis via bloodstream
Lymphomas have their own system of staging. What is this?
Ann Arbor staging
• Stage I - lymphoma in a single node region
• Stage II - indicates two seperate regions on one side of the diaphragm
• Stage III - spread to both sides of the diaphragm
• Stage IV - diffuse or disseminated involvement of one or more extra lymphatic organs such as bone marrow or lungs
Colorectal carcinoma has its own system of staging. What is it?
Dukes’ staging
• Dukes’ A - invasion into but not through the bowel
• Dukes’ B - invasion through the bowel wall
• Dukes’ C - involvement of lymph nodes
• Dukes’ D - distant metastases
What is tumour grade?
Tumour grade describes the degree of differentiation of a neoplasm.
Is tumour stage or tumour grade subjective?
Grade - describes the degree of differentiation of a neoplasm
How are tumours graded?
- G1 - well-differentiated
- G2 - moderately differentiated
- G3 - poorly differentiated
- G4 - undifferentiated or anaplastic
What is the internationally recognised formal grading system for breast cancer called?
Bloom-Richardson system
What does the Bloom-Richardson system assess?
- Tubule formation
- Nuclear variation
- Number of mitosis
Tumour grade is more important for planning treatment and estimating prognosis in certain types of malignancy. Name them.
- Soft tissue sarcoma
- Primary brain tumours
- Lymphomas
- Breast cancer
- Prostate cancer
What is the curative treatment for most cancers?
Surgery
How is radiotherapy used to treat cancer?
X-rays or other types of ionising radiation are used to kill proliferating cells by triggering apoptosis or interfering with mitosis due to damage to DNA (particularly during G2)
• Triggering apoptosis - high dosage causes either direct or free-radical induced DNA damage that is detected by the cell cycle check-point during G2, triggering apoptosis before M phase
• Interference with mitosis - double stranded DNA breakages cause damaged chromosomes that prevent the M phase from completing correctly
How is damage of healthy tissue minimised when treating cancer with radiotherapy?
- Radiotherapy is focused on the tumour with shielding of surrounding healthy tissue
- Given in fractionated doses
What are the main types of chemotherapy and how do they work?
• Antimetabolites
mimic normal substrates involved in DNA replication eg. Fluorouracil
• Alkylating and platinum-based drugs
cross-link the two strands of the DNA helix eg. Cyclophosphamide and cisplatin (testicular cancer)
• Antibiotics
several methods eg.
Doxorubicin - inhibits DNA topoisomerase needed for DNA synthesis
Bleomycin - causes double-strand DNA breaks
• Plant-derived drugs eg.
vincristine - blocks microtubule assembly and interferes with mitotic spindle formation
Why is hormone therapy advantageous over chemotherapy and radiotherapy?
It is relatively non-toxic (but only available for certain malignant tumours)
Which hormone can treatment can be used to treat hormone receptor-positive breast cancer?
Selective oestrogen receptor modulators (SERMs) Eg. Tamoxifen
They bind to oestrogen receptors, preventing oestrogen from binding.
Blockade of which class of hormones is used in the treatment of prostate cancer?
Androgens
Describe how oncogenes can be targeted by cancer therapy.
Identifying cancer-specific alterations such as oncogene mutations allows drugs to be targeted specifically at cancer cells.
Describe how Herceptin works.
- A quarter of breast cancers have gross over-expression of the HER-2 gene
- Herceptin can block HER-2 signalling
Describe how Imatinib works.
- Chronic myeloid leukaemia (CML) shows a chromosomal rearrangement (t9:22) creating an abnormal ‘philadelphia’ chromosome in which an oncogene gusion protein (BCR-ABL) is encoded
- Imatinib inhibits the fusion protein.
What is adjuvant treatment?
Treatment given after surgical removal of a primary tumour to eliminate subclinical disease (used to treat cancers known to have micrometastases)
What is neoadjuvant treatment?
Treatment given to reduce the size of a primary tumour prior to surgical excision.
What are tumour markers and how are they used?
Various substances are released by cancer cells into the circulation. Although some have role in diagnosis, in general, they are most useful for monitoring tumour burden during treatment and follow up. They include:
- hormones
- oncofetal antigens
- specific proteins
- mucins and glycopeptides
Human chorionic gonadotropin (HCG) is an example of a _______ released by ________
Hormone
Testicular tumours
Alpha feroprotein (AFP) is an example of a ________ released by _______
Oncofetal antigen
Hepatocellular carcinoma
Prostate specific antigen (PSA) is an example of a specific protein released by ________
Prostate carcinoma
Cancer antigen 125 is an example of _________ released by ______
Mucins/glycopeptides
Ovarian cancer
What is the aim of cancer screening?
Attempts to detect cancers as early as possible when the chance of cure is the highest by looking for early signs of disease in healthy people.
What are the problems associated with cancer screening?
• Lead time bias
◦ Although 5-year survival seems to improve, it has not. Cancer has just been detected earlier.
• Length time bias
• Over diagnosis
◦ Screening picks up slow growing benign tumours that would not have turned malignant and would be asymptomatic so we think we have detected more cases but we haven’t
For which cancers are there established national screening programmes for in the UK?
Cervical
Breast
Colorectal
Why is TNM staging not used for leukaemia?
TNM system is for solid tumours
Leukaemia is a ‘liquid tumour’
What is anthracosis?
Blackened lungs
