Session 1 Flashcards
Define disease
Pathological condition of a body part, organ or system characterised by an identifiable group of signs or symptoms
What is pathology?
The study of suffering (disease and cellular dysfunction)
Cytopathology involves the study of…
Disaggregated cells rather than tissues to study disease
Histopathology involves the study of…
Tissues to study disease
Give examples of histologcal procedures (3)
Core biopsies
Cancer resection specimens
Excised skin lesions
Give examples of cytological procedures (2)
Fine needle aspirates of breast/thyroid/salivary glands
Cervical smears
Give 2 advantages of histological investigations/procedures over cytological investigations/procedures
Often therapeutic as well as diagnostic
Can assess architecture as well as cell atypia
Give 3 advantages of using cytological procedures/investigations over histological procedures/investigations
Faster and cheaper
Non-invasive or minimally invasive
Can be used for cells in fluid
The staging of cancer often follows the TNM system which looks at…
Tumour
Nodes
Metastases
What is autolysis? How can this affect microscopy of a tissue?
Self digestion of a tissue which occurs when the blood supply is cut off
Destroys cell and tissue architecture
How can autolysis be prevented?
By use of fixatives that inactivate tissue enzymes, prevent bacterial growth and harden the tissue
What chemical is typically used in fixation of sample for microscopy? What change in appearance will the tissue show after the fixative is applied?
Formalin
Raw meat —> Cooked meat
Tissues that have been fixed are placed into a ________ with holes in it to allow the chemical to penetrate the sample
Cassette
Why is it important for the tissue to be hard? What is this process called?
Allows the tissue to be cut into very thin slices
Embedding
What is commonly used as the hardening agent when a tissue is embedded?
Paraffin wax
Outline the process of embedding a tissue
Dehydration using alcohol in a vacuum
Alcohol replaced with xylene as it can mix with wax
Xylene replaced with molten paraffin wax
Tissues are typically cut to what thickness? Using which piece of equipment?
~3-4 microns
Microtome
What stain is most commonly used to stain samples?
H & E stain
Haematoxylin + Eosin
What does haematoxylin stain the most?
The nucleus most strongly blue
What does eosin stain the most?
The EM (cytoplasm and connective tissue) most strongly pink
What is the purpose of mounting a slice of tissue?
Preserves and protects the sample
What does immunohistochemistry involve?
Demonstrates substances in/on cells by labelling them with specific antibodies. These antibodies are usually linked to an enzyme that catalyses a colour-producing reaction.
What are cytokeratins? What is the clinical significance of these?
Family of intracellular fibrous proteins present in epithelial cells
They are markers for epithelial differentiation and show a tissue specific distribution in epithelia. So they can be used to show whether a cancer is a carcinoma and its primary site depending on the combination of different cytokeratins found
Why are frozen sections sometimes taken?
It’s a method of hardening tissue quickly - useful intra-operatively as it gives a quick result and can influence the course of the operation
Why are frozen sections not routinely used?
They provide a lower quality sample - cell morphology is not as good as in paraffin sections
What piece of equipment is used to take frozen sections?
A cryostat (microtome inside a freezer)
What is hypoxia?
Decreased oxygen supply to certain cells/tissues
What is ischaemia?
Decreased blood supply to certain cells/tissues
Why is ischaemia worse than hypoxia?
In ischaemia other nutrients such as glucose are also not supplied to cells/tissues
Name 4 types of hypoxia
Hypoxaemic hypoxia
Anaemia hypoxia
Ischaemic hypoxia
Histiocytic hypoxia
What is hypoxaemic hypoxia? Give an example of a cause
Where the arterial content of oxygen is low - e.g. There is reduced absorption of oxygen in the lungs
What is anaemic hypoxia? Give an example of a cause
Where there is decreased ability of haemoglobin to carry oxygen (e.g. In anaemia)
What is ischaemic hypoxia? Give an example of a cause
Where there is interruption to blood supply (e.g. There is blockage of a vessel)
What is histiocytic hypoxia? Give an example of a cause
The inability to utilise the oxygen within cells (e.g. Damaged oxidative phosphorylation enzymes due to cyanide poisoning)
The effects of hypoxia depends on…
Which cells/tissues it is affecting, some cells are damaged more quickly by hypoxia
E.g. Neurones last a few minutes, Fibroblasts last a few hours
What are hypersensitivity reactions?
Where the host tissue is injured secondary to an overly vigorous immune reaction
What are autoimmune reactions?
Immune system fails to distinguish self from non-self
What are free radicals?
Reactive oxygen species that have a single unpaired electron in its outer orbit making it unstable and more reactive
What are 3 significant free radicals? Which is the most dangerous?
OH* (hydroxyl)
O2- (superoxide)
H2O2 (hydrogen peroxide)
Hydroxyl
How are free radicals produced? (5)
Normal metabolic reactions - e.g. Oxidative phosphorylation
Inflammation - oxidative burst of neutrophils is used to kill microorganisms
Radiation - converts water to hydroxyl
Contact with unbound metals within the body (e.g. Fe/Cu)
Drugs (e.g. Metabolism of paracetamol in the liver)
Haemachromatosis is caused by…
Excess of iron
Wilson’s disease is caused by…
Excess of copper
What controls do we have against free radicals? (3)
Anti-oxidant system
Metal carrier and storage proteins
Enzymes that neutralise free radicals
What does the anti-oxidant system consist of? How does it work against free radicals?
Vitamins A, C & E
They donate electrons to the free radical
Give an example of a metal carrier protein that sequesters…
(I) iron
(II) copper
Transferrin
Ceruloplasmin
Give 3 examples of enzymes that neutralise free radicals.
Superoxide dismutase
Catalase
Glutathione peroxidase
How do free radicals injure cells?
They injure cell membranes and cause lipid peroxidation and then further free radicals
What is oxidative imbalance?
Where the number of free radicals overwhelms the anti-oxidant system
As well as lipids, which other cell structures can be oxidised by free radicals? What are the consequences of this?
Proteins, carbohydrates, DNA
Causes mutations in DNA and can therefore be carcinogenic, also bends proteins out of shape
What is the function of heat shock proteins?
During any cell injury, these proteins stop producing their usual products and aim to mend mis-folded proteins
What is karyolysis?
Nuclear fading - dissolution of chromatin due to action of DNAases and RNAases leading to cell death
What is pyknosis?
Nuclear shrinkage - DNA condenses into shrunken basophilic mass leading to cell death
What is karyorrhexis?
Nuclear fragmentation - nuclear membrane ruptures and nucleus undergoes fragmentation leading to cell death
How will injured cells appear under the microscope?
Often pale and swollen due to poorer function of the membrane
Hypoxia can result in cytoplasmic changes, nuclear changes and abnormal cellular accumulations seen under the microscope what is an example of these abnormal accumulations?
Fat in hepatocytes
What is an example of a reversible change that can be seen in an injured cell under an electron microscope?
Blebbing because the cytoskeleton is being broken down by proteases
How can cell death be diagnosed?
Cells placed in fluid with a dye - dead cells with non-functioning membranes will take up the dye
What is oncosis?
Cell death with swelling, the spectrum of changes that occur in injured cells prior to death
What is necrosis?
In a living organism, the morphological changes that occur after a cell has been dead some time (after 12-24 hours)
Name 4 types of necrosis
Coagulative
Liquefactive
Caseous
Fat
Coagulative necrosis takes place in which sorts of tissues?
Solid organs with a lot of connective tissue support e.g. Kidneys
Liquefactive necrosis takes place in which sorts of tissues?
Loose tissues e.g. Brain
What happens in coagulative necrosis?
Denaturation of proteins dominates over the release of active proteases
How does coagulative necrosis look under the microscope?
The cellular architecture is somewhat preserved with the ‘ghost outline’ of cells
What happens in liquefactive necrosis? How does it appear under the microscope?
Enzyme degradation is substantially grater than denaturation and there is enzymatic degradation of tissues
resulting in no cell architecture being seen under the microscope
What is caseous necrosis? In what cases is it most common?
Contains amorphous (structureless) debris - ‘cottage cheese’ appearance
In infections - especially TB
What type of necrosis is particularly associated with infections such as TB?
Caseous necrosis
Give two examples of where fat necrosis can be seen?
In pancreatitis
In the breast
What happens in pancreatitis with regards to fat necrosis?
Digestive enzymes leak out into the abdominal cavity and break down lipids into fatty acids. Fatty acids react with calcium to form calcium soaps which are then deposited.
What happens in the breast with regards to fat necrosis?
There is disruption of fat in the breast and a hard lump forms in the breast
What is gangrene?
Necrosis visible to the naked eye
What is dry gangrene?
Visible necrosis modified by exposure to air - commonly coagulative necrosis
What is wet gangrene?
Visible necrosis modified by infection - commonly liquefactive necrosis
What is gas gangrene?
Wet gangrene where the infection is with anaerobic bacteria that produce gas
What is an infarction?
Necrosis caused by reduction in arterial blood flow
What is an infarct?
An area of necrotic tissue which is the result of loss of arterial blood supply
Name two common causes of infarction
Thrombosis
Embolism
Infarcted tissue can appear which two colours?
White or red
Where are white infarcts most common? What causes them? What is the reason for their appearance? What type of necrosis is commonly associated with white infarcts?
Solid organs e.g. Kidneys
There is usually occlusion of an end artery with no collateral blood supply
There is no blood haemorrhage into the area giving a white appearance
Coagulative
Where do red infarcts commonly take place? What is the reason for their red appearance?
Loose tissues e.g. Lungs
There is haemorrhage into necrotic areas. There is often a dual blood supply with not enough blood to rescue the area but blood still pumping.
What is ischaemia-reperfusion injury?
Worse damage that results from reperfusing ischaemic tissues. Results in…
Increased production of oxygen free radicals
Increased number of neutrophils and more inflammation
Activation of the complement pathway
Leaky membranes can cause molecules to leak out of cells as well as in. What can leak out? What effect can each molecule have?
Potassium
Enzymes
Myoglobin
What can too much calcium outside a cell result in?
Cardiac arrest
Myoglobin can leak out of damaged skeletal muscle cells in response to…
What can it result in? (2)
Trauma/Extreme Exercise
Brown urine and renal failure
What is apoptosis?
Cell death with shrinkage
Does apoptosis require ATP?
Yes
How does apoptosis work?
Activates enzymes that degrade its own nuclear DNA and proteins
How is DNA broken down in apoptosis? How is DNA broken down in oncosis?
Inter-nucleosomal cleavage of dna
Random cleavage of DNA
How is membrane integrity affected in apoptosis? Are lysosomal enzymes involved in apoptosis? How fast is the process of apoptosis?
Membrane integrity is maintained
No
Quick - few hours
Give 3 physiological examples of apoptosis in the human body.
To maintain a steady number of cells
To reduce the size of ovaries after removal of oestrogen in post menopausal women
Apoptosis between the digits on a human hand
Give 3 examples of pathological apoptosis in the human body.
Cytotoxic T cell killing of virus infected or neoplastic cells
Damaged cells with damaged DNA
Graft versus host disease
What are the 3 phases of apoptosis?
Initiation
Execution
Degradation & Phagocytosis
Apoptosis can be activated via ___________ or ___________ pathways. Both pathways result in the activation of ___________
Extrinsic or intrinsic
Caspases
What are caspases?
Enzymes that control and mediate apoptosis, cause the cleavage of DNA + proteins
What is meant by the intrinsic pathway of apoptosis? What typically triggers it?
Everything happens within the cell
Irreparable DNA damage
What happens in the intrinsic pathway of apoptosis?
P53 protein is activated —-> Outer mitochondrial membrane becomes leaky —-> Cytochrome C is released from the mitochondria —-> Activation of caspases
What is meant by the extrinsic pathway of apoptosis? What typically triggers it?
Initiated by extracellular signals
Cells that are a danger e.g. Tumour cells/virus infected cells
What happens in the extrinsic pathway of apoptosis?
E.g. TNFalpha secreted by t killer cells in response to cells that are a danger —-> Bind to cell membrane death receptor (death receptor) —-> Activation of caspases
What happens to the apoptotic bodies produced in the intrinsic/extrinsic pathways?
They express proteins on their surface that allow them to be recognised, phagocytosed and degraded by phagocytes or neighbouring cells
Why does cellular accumulation occur?
As a result of a cell not being able to metabolise something
What is meant by the term hydropic swelling?
Accumulation of fluid
When does fluid accumulation occur?
When energy supplies are cut off - e.g. In hypoxia
What happens in fluid accumulation?
Na+ and water flood into the cell
Why is cerebral oedema a particular problem?
Increased pressure on the skull, structures in the brain/spinal cord get compressed - blood supply may be compromised
What is steatosis? Where is it commonly seen and why?
The accumulation of triglycerides in a cell
The liver as it is a major organ of fat metabolism
What are some common causes of steatosis?
Alcohol
Diabetes
Obesity
Cholesterol can only be eliminated through the _______
Liver
Is cholesterol soluble or insoluble?
Insoluble
How is excess cholesterol stored?
In cells within vesicles
In particular what two types of cells can cholesterol accumulate in?
Smooth muscle cells and macrophages
Produces foam cells
How do accumulated proteins appear under the microscope?
As eosinophilic droplets in the cytoplasm
What protein accumulations are seen in alcoholic liver disease?
Mallory’ hyaline - accumulation of damaged keratin filaments
What causes alpha1-antitrypsin deficiency? What can it result in?
Incorrectly folded a1-antitrypsin proteins - accumulates in ER and leads to deficiencies as a result
Can lead to emphysema as proteases act unchecked in the lungs
What are some examples of exogenous pigments that can accumulate in the body?
Air pollutants such as carbon, coal dust, soot
What happens to pigments such as soot that are inhaled?
They are phagocytosed by alveolar macrophages resulting in anthracosis (blackening of the lungs) and blackened peribronchial lymph nodes
Small amounts of pigment accumulation is usually harmless. Large amounts can result in…
Fibrosis and emphysema (coal worker’s pneumoconiosis)
What happens to some of the pigment following a tattoo…
Some reaches and stays in the draining lymph nodes
What is haemosiderin?
An endogenous pigment and iron storage molecule derived from haemoglobin
What colour does haemosiderin have?
Yellow/brown colour
When does haemosiderin form?
When there is a systemic or local excess of iron
What happens when there is a systemic excess of iron?
Haemosiderosis - it is deposited in organs
What can cause haemosiderosis? (3)
Haemolytic anaemia, blood transfusions and hereditary haemochromatosis
What is the result of hereditary haemochromatosis?
Increased intestinal absorption of dietary iron and deposition of iron in organs (haemosiderosis).
What are some symptoms of hereditary haemochromatosis?
Liver damage, heart dysfunction and endocrine failures
What is the treatment for hereditary haemochromatosis?
Repeated bleeding?
Jaundice is as a result of the accumulation of…
What colour does it have?
Bilirubin
Bright yellow
How is bilirubin formed? In which cells of the body?
As a breakdown product of heme
All cells of the body
How is bile excreted?
Taken from tissues bound to albumin to the liver and excreted in the bile
When does jaundice occur?
When bile flow is obstructed or overwhelmed
Where is bilirubin deposited in jaundice?
Extracellularly or in macrophages
What is meant by the calcification of tissues?
Abnormal deposition of calcium salts within tissues
Calcification of tissues can either be localised (___________) or generalised (__________)
Dystrophic
Metastatic
Is dystrophic calcification more or less common than metastatic calcification? When does it occur? (5)
More common
In areas of dying tissue, atherosclerotic plaques, ageing or damaged heart valves, TB lymph nodes, malignancies
What happens in metastatic calcification?
Hypercalcaemia in the blood as a result of abnormal calcium metabolism results in calcium hydroxyapatite crystals being deposited in normal tissues throughout the body
What are two main causes of hypercalcaemia?
Increased secretion of parathyroid hormone (PTH) resulting in bone resorption (can be primary, secondary or ectopic)
Destruction of bone tissue
After a certain number of divisions cells reach ____________ _____________ where they can no longer divide. This is related to the length of their ___________.
Replicative senescence
Telomeres
What is the function of telomerase? Which types of cells produce telomerase?
Maintains the length of telomeres so cells can continue to replicate
Germ cells, stem cells and cancer cells
