Pathological Processes - Semester 2 Flashcards
What is the difference between HISTOLOGY and CYTOLOGY?
HISTOLOGY - involves viewing tissue sections under microscope; cellular architecture and atypia are assessed; higher accuracy than cytology; more invasive
CYTOLOGY - non-invasive; fast, cheap and safe; used in preliminary testing; study of cells sucked out / scraped from an organ or extracted from a body fluid
What is the most commonly used fixative?
Formalin (formaldehyde in water)
What does a ‘fixative’ do?
Holds tissue in suspended animation Inactivates tissue enzymes Denatures proteins Blocks autolysis Hardens tissue Prevents bacterial growth
What is used to embed the fixed tissue for histological examination?
paraffin wax
What is a ‘microtome’ used for in the preparation of a slide for microscopy?
Microtome cuts thin slices (3-4 microns thick) so that you can see through the sections using a microscope
What does H&E stand for?
haematoxylin
eosin
What does haematoxylin stain, and what colour?
Haematoxylin stains nuclei purple
What does eosin stain, and what colour?
Eosin stains cytoplasm, proteins, collagen and CT pink
In what situation might a frozen section be necessary instead of histology?
Time constraints - is this tissue cancerous or not?
The result will determine the course of the surgery.
How is a frozen section produced?
(bypass formalin fixation and paraffin wax embedding)
Rapidly freeze small fresh piece of tissue using the CRYOSTAT
Thinly slice the piece of tissue
Stain tissue
Mount and view using microscope
Give 4 causes of cell injury and death
Hypoxia (anaemia, ischaemia, histocytic, hypoxaemia)
Physical agents (trauma, radiation, electric currents)
Chemical agents and drugs (poisons, O2 extremes, alcohol)
Microorganisms
Immune mechanisms
Dietary insufficiency/excess
Genetic abnormalities
How does hypoxic injury occur?
Cell deprived of O2
Mitochondrial ATP production stops
Slowed down activity of ATP driven membrane ionic pumps
Na+ and H2O enter the cell
Cell swells, plasma membrane stretches
Glycolysis allows cell to stay alive temporarily (so increased lactic acid and decreased pH)
Heat shock response
Ca2+ enters cell, activating harmful enzymes (phospholipases, ATPase, endonucleases, proteases)
ER and other organelles swell
Enzymes leak out of lysosomes and attack cytoplasmic components
Blebbing
Cell dies (burst of bleb)
Why is it sometimes worse if blood returns to the tissue that has been ischaemic but isn’t yet necrotic THAN if blood flow hadn’t been restored?
Ischaemic-reperfusion injury
What is the mechanism of ischaemic-reperfusion injury?
Increased production of O2- free radicals with reoxygenation
More neutrophils, more inflammation and tissue injury
Delivery of complement proteins and activation of the inflammation pathway
Define “free radical”
Highly reactive, uncharged atom/molecule with a single unpaired electron in an outer orbit. Goes on to produce more free radicals. A reactive oxygen species with a single unpaired electron on the outer orbit.
How do free radicals injure cells?
Free radicals attack lipids in cell membranes, damage proteins, carbohydrates and nucleic acids. They are mutagenic.
How does the body defend itself against free radicals?
Antioxidant system Vitamins A, C and E Enzymes Free radical scavengers Storage proteins
What protein do cells release when they are injured (in order to protect themselves) and what does this protein do?
Heat shock proteins (e.g. ubiquitin)
Maintains protein viability and maximises cell survival
Characteristics of reversible cell injury under an electron microscope (3)
clumped chromatin
cell organelles swell
cytoplasmic blebs
ribosomes separate from the ER
Characteristics of irreversible cell injury under an electron microscope (3)
Increased cell swelling karyolysis membrane defects lysis of ER densities in swollen mitochondria myelin figures
What is the difference between oncosis and necrosis?
Oncosis is the changes to the injured cell prior to death
Necrosis is the changes to the dead cell after it has been dead for some time
What is the difference between necrosis and apoptosis?
Necrosis - cell died with swelling; due to cell injury
Apoptosis - programmed cell suicide; cell died with shrinkage; regulated intracellular process where the cell itself degrades its own nuclear DNA and proteins
How is necrotic tissue removed from an area?
Phagocytosis by white cells
Enzymatic degradation
If some tissue remains, it calcifies - DYSTROPHIC CALCIFICATION
What are the four types of necrosis?
Coagulative
Liquifactive
Caseous
Fat
Name a disease that characteristically results in caseous necrosis
Tuberculosis
What is the difference between coagulative necrosis and liquifactive necrosis?
Coagulative necrosis - solid organs - proteins denature and coagulate
Liquifactive necrosis - loose tissues - proteins undergo autolysis
What is the difference between gangrene and necrosis?
Gangrene is necrosis visible to the naked eye
What is the relationship between infarction and ischaemia?
Ischaemia (restriction of blood supply) —-> infarction (death of tissue)
What are the two types of infarction?
Red (hemorrhagic)
White (anaemic) - after occlusion of an end artery
Name a molecule that leaks out from an injured cell
Myoglobin
Enzymes
Potassium
Under a light microscope, how does a cell undergoing apoptosis appear?
Shrunken
Eosinophilic
Chromatin condensation
Fragmentation of nucleus - karyorrhexis
Under an electron microscope, how does a cell undergoing apoptosis appear?
Cytoplasmic BUDDING (NOT BLEBBING)
________ control and mediate apoptosis
CASPASES
Which abnormal protein accumulates in alcoholic liver disease?
Mallory’s hyaline
Give an example of a reason for exogenous pigment accumulation
Coal dust, tattoo
Give an example of a reason for endogenous pigment accumulation
Haemosiderin
Bilirubin (jaundice)
What are the two causes of pathological calcification?
Dystrophic
Metastatic
What is the difference between dystrophic and metastatic calcification?
Dystrophic - localised in one area of dying tissue, no abnormality in Ca2+ metabolism
Metastatic - body-wide/generalised, abnormality in Ca2+ metabolism
Give 3 consequences of cellular aging.
Accumulation of damage to DNA
Accumulation of damage to cellular components
Accumulation of abnormally folded proteins
Accumulation of lipofuscin pigment
Reduced ability to replicate
Give 2 effects on liver of chronic excessive alcohol intake
Fatty change
Cirrhosis
acute alcoholic hepatitis
Acute inflammation is a rapid response to an injurious agent that aims to do what?
Deliver mediators of host defence (leucocytes and plasma proteins) to the site of injury and so limit tissue damage, protect against infection, clear damaged tissue
Acute inflammation is carried out by:
a) innate immune system, or
b) adaptive immune system?
a) innate immune system
What is the difference between exudate and transudate?
Exudate - protein rich - develops in inflammation
Transudate - protein poor - e.g. seen in heart failure
Give 3 major causes of acute inflammation
Microbial infections Acute phase hypersensitivity reactions Physical agents Chemicals Tissue necrosis
5 cardinal signs of infection:
Rubor Dolor Calor Tumor Loss of function
Name the 3 tissue changes in acute inflammation:
Vascular flow
Formation of a fluid exudate
Neutrophil emigration
Explain the change in blood flow that occurs in acute inflammation
Arterioles vasodilate
Acceleration of flow in arterioles and capillaries
Increased capillary pressure
Why is an increased capillary flow important in acute inflammation?
Increased delivery of fluid and leucocytes to injured area
What is the main force pushing fluid out of blood vessels?
capillary hydrostatic pressure
What is the main force pushing fluid into blood vessels?
colloid osmotic pressure
In four steps, explain how vascular leakage occurs in acute inflammation.
1) Endothelial contraction —-> gaps
2) Plasma proteins leak into interstitial space
3) Upstream vessel dilates
4) Net flow of fluid out of vessels - OEDEMA
Why is a fluid exudate useful in acute inflammation?
Delivers plasma proteins to site of injury
Excess fluid drains in the lymphatics taking antigens + microorganisms with it, presenting them to lymph nodes
Neutrophils are “end cells”. What are end cells?
Cannot multiply
Give the four steps how neutrophils get out of the vessels to kill microorganisms:
1) Margination - neutrophils line up on the edge of the vessel due to stasis
2) Rolling - Neutrophils roll along the endothelial surface
3) Adhesion - stick to the endothelium
4) Emigration
Then recognition, attachment and phagocytosis
Give four important chemical mediators in acute inflammation
Histamine Bradykinin Prostaglandin Complement system Cytokines and chemokines
What is the effect of prostaglandin?
Makes skin more sensitive to pain and causes fever
Which medication stops the production of prostaglandin?
NSAIDs and aspirin
What is the effect of histamine on the body?
Burning pain
increased vascular permeability
vasodilation
Which cells store histamine in the body?
Mast cells, basophils and platelets
How does the complement system kill bacteria?
Punches holes in bacteria
Causes inflammation also
C3b is an opsonin, aiding the phagocytosis of antigens
What is the function of a cytokine, such as TNF?
Messengers between cells
Give three local complications of acute inflammation
Damage to normal tissue
Obstruction of tubes, compression of vital structures
Loss of fluid
Pain and loss of function
Give three systemic complications of acute inflammation
Fever
Leucocytosis (increaased leucocytes circulating)
Acute phase response
Shock
Give 3 types of exudate
Pus
Hemorrhagic
Serous
Fibrinous
Give the type of inflammation (acute or chronic), a complication and causative organism of LOBAR PNEUMONIA
acute exudative inflammation secondary to airborne infection of the entire pulmonary lobe
by Streptococcus pneumoniae/pneumococcus
complication: lung abscess, pleural effusion, lung fibrosis
Name a causative organism of ascending cholangitis
E. coli
Name one inherited disorder of the acute inflammatory process
Hereditary angio-oedema - inherited deficiency of C1-esterase inhibitor, attacks of non-itchy cutaneous angio-oedema
Alpha-1 antitrypsin deficiency - so proteases released from neutrophils act unchecked and damage normal lung and liver tissue as they are not deactivated
Chronic granulomatous disease - phagocytes cannot generate the oxygen burst
What is chronic inflammation?
CHRONIC response to injury with associated fibrosis
What is the difference between chronic and acute inflammation?
Fibrosis
Chronic takes over acute after a few hours if the injurious agent is not removed
What are the dominant cells in chronic inflammation?
Macrophages
Lymphocytes
Give a disease where chronic inflammation occurs without any preceding acute inflammation.
TB
autoimmune diseases
toxic agents
Give the THREE main roles of macrophages in chronic inflammation
Phagocytosis
Produces important proteins and enzymes
Controls other cells via cytokine release
Presentation of antigens to immune system
What is the major difference in role between T and B lymphocytes?
T - cytotoxic functions
B - makes antibodies
What are macrophages called when they are circulating in the blood?
Monocytes
Do macrophages replicate?
Yes, unlike neutrophils!
Are lymphocytes usually present in tissues?
No! So their presence indicates antigenic material has been there.
Which cell type dominates in allergic reactions / parasitic infections?
Eosinophils
Which type of giant cell is characteristic of tuberculosis?
Langhan’s giant cell
What are the three kinds of giant cells involved in chronic inflammation?
Touton - lesions with high fat content
Langhan’s - TB
Foreign body
Give three possible complications of chronic inflammation
XS fibrosis - e.g. cirrhosis
Impaired function - e.g. Crohn’s
Tissue destruction - e.g. healthy tissue taken over by fibrosis
Atrophy
Define the term “granuloma”
organised collection of macrophages
In which case would granulomatous inflammation occur?
Granuloma forms around a particle that is DIFFICULT TO DISSOLVE in an effort to destroy it.
What are the two types of granulomas?
Foreign body and Hypersensitivity granulomas
What is the difference between foreign body and hypersensitivity granulomas?
Foreign body - forms around material that is NOT antigenic
Hypersensitivity - forms around material that IS antigenic
Which kind of cells make up a foreign body granuloma
Lymphocytes surrounding epitheloid cells
In TB, you also have caseous necrosis at the centre of the granuloma plus Langhan’s giant cells involved too
What is the role of thrombin in clot formation?
Thrombin: fibrinogen —> fibrin (insoluable)
What is the name of the process by which clots are DESTROYED?
Thrombolysis
What are the three steps of haemostasis?
1) Severed artery contracts
2) Primary haemostatic plug of activated platelets
3) Secondary haemostatic plug of fibrin filaments (about 30 mins after initial injury)
Which cell produces PLATELETS?
Megakaryocytes
Name two platelet activators.
Collagen surfaces
ADP (released from activated platelets and injured RBCs)
Thrombin
Thromboxane
Once activated, what do platelets stick to?
Activated platelets stick to von Willebrand factor on the exposed subendothelium
In one simple statement, how does aspirin prevent clotting?
Inactivates an enzyme involved in platelet aggregation (thromboxane A2)
How does thrombin become activated?
Clotting factors
Some clotting factors require Vitamin __ for their synthesis
K
What is the difference between intrinsic and extrinsic pathways to blood clotting?
Intrinsic - all factors contained in blood and no vessel needs to be broken to kickstart the process
Extrinsic - needs a “tissue factor” which is not present in blood
Name an endothelial secretion that opposes blood clotting
tissue plasminogen activator
thrombomodulin
Name an endothelial secretion that favours blood clotting
Von Willibrand factor
Tissue factor
____ __________ helps to pull the sides of small wounds together and may toughen the clot by squeezing water out
CLOT RETRACTION
Name 2 plasminogen activators
Streptokinase
Urokinase
Tissue plasminogen activator
What is the role of plasmin?
Dissolves fibrin (fibrinolysis) and therefore thrombi and thromboemboli
How does the clotting cascade set fibrinolysis in motion?
Becauses fibrin increases the activity of tissue plasminogen activator which produces plasmin which causes fibrin —-> FDPs
Name one inherited bleeding disorder
Haemophilia A + B
Von Willebrand Disease
How do patients with haemophilia present?
Haemorrhage post-surgery
Easy bruising
Recurrent bleeding into joints
Petechiae
What kind of disease is haemophilia in terms of how it is associated with chromosomes?
X linked recessive
How can you diagnose haemophilia using blood coagulation tests? e.g. platelet count, bleeding time, PT, APTT
normal platelet count
normal bleeding time
normal PT (so extrinsic pathway is fine)
BUT abnormal APTT (so intrinsic pathway is affected)
What really is the problem in people with haemophilia?
Cannot produce enough fibrin so impaired clotting despite normal platelets
What is the problem in people with von Willebrand disease?
Deficient / abnormal vWF
How can you diagnose von Willebrand disease using blood coagulation tests? e.g. platelet count, bleeding time, PT, APTT
Raised bleeding time raised APTT (because platelets "stick less" to the endothelium so less platelet aggregation and hence, clotting)
What is the inheritance pattern of von Willebrand disease?
Autosomal dominant
What is thrombocytopenia?
Low platelet count
How does thrombocytopenia show up in blood coagulation tests?
prolonged bleeding time
normal PT + APTT (as extrinsic and intrinsic pathways are intact, the problem is the platelets!)
Give three causes of thrombocytopenia
Sequestration e.g. hypersplenism
Dilutional e.g. after blood transfusion
Decreased platelet survival e.g. immunological destruction, non-immunological destruction (DIC)
Decreased platelet production e.g. bone marrow infiltration by malignancy, drugs (cytotoxic)
Give 1 cause of thrombophilia
Protein C/S deficiency
antithrombin deficiency
What is disseminated intravascular coagulation?
clotting activator gets into blood and microthrombi are formed throughout the circulation, using up fibrin, platelets and coagulation factors and causing haemorrhage
Give three causes of DIC
sepsis severe trauma extensive burns snake bites malignancy
What is the treatment for DIC?
TREAT THE CAUSE
Give 2 ACQUIRED coagulation factor disorders
Anticoagulants e.g. warfarin
liver disease
Vitamin K deficiency
Regeneration (of cells) only occurs in ____ / _____ tissues (NB, not a type eg muscle, rather the general name for a group of these tissues!)
labile
stable
What is also known as “healing by primary intention”?
regeneration
What is also known as “healing by secondary intention”?
fibrous repair
Why does healing by fibrous repair occur in some cases instead of just regeneration?
Significant tissue loss/ if collagen or CT framework is destroyed
Ongoing chronic inflammation
Give an example of a labile tissue
Surface epithelia of bone marrow
Haemopoietic tissues
Columnar epithelia of GI tract and uterus
Give an example of a permanent tissue
Cardiac muscle cells
Skeletal muscle cells
Neurons
Give an example of a stable tissue
Resting lymphocytes
Bone
Parenchymal cells of liver, kidneys, pancreas
What is the difference between labile, stable and permanent tissues?
Labile - continuously dividing tissues as cells are short lived
Stable - rapid division in response to stimuli, quiescent
Permanent - non-dividing tissues
Stem cells undergo assymetric replication. What does this mean?
When the stem cell divides, it produces a stem cell like itself and a differentiated cell
Give 2 places where stem cells can be found in the body
Liver, between hepatocytes and bile ducts
Epidermis, in basal layer
Intestinal mucosa, at bottom of crypts
What is the difference between totipotent, multipotent and unipotent stem cells?
Unipotent - produces one type of differentiated cell
Totipotent - produces ANY type of differentiated cell (this is an embryonic stem cell)
Multipotent - produces several types of differentiated cell
Give an example of a multipotent stem cell
Haemopoietic stem cell of the bone marrow
Which three cell types are involved in fibrous repair?
Inflammatory cells like neutrophils, macrophages which phagocytose the debris
Endothelial cells (angiogenesis)
Fibroblasts and myofibroblasts
What are the four steps of the fibrous repair process?
Phagocytosis… of necrotic tissue debris
Proliferation… of epithelial cells - angiogenesis
Proliferation… of fibroblasts and myofibroblasts which synthesise collagen and cause wound contraction
Fibrous scar…. forms then matures and shrinks (myofibroblasts)
Enzymatic modification of the polypeptide alpha chain in collagen synthesis involves hydroxylation which requires Vitamin ___.
vitamin C
In collagen synthesis, procollagen is cleaved to produce _______ which goes on to polymerize, forming fibrils.
TROPOCOLLAGEN
At the last step of collagen synthesis, cross linkage of collagen fibres increases ____ ______
tensile strength
Name an acquired condition that results in defective collagen synthesis?
Scurvy
In which cellular component does the intracellular part of collagen synthesis occur?
Endoplasmic reticulum
Name three inherited conditions which result in defective collagen synthesis.
Osteogenesis imperfecta
Ehlers-Danlos Syndrome
Alport syndrome
What are 3 characteristic features of Ehlers-Danlos syndrome?
Hyperextensible skin, fragile skin, hypermobile joints, poor wound healing