ICS - Pathology Flashcards
Two different types of autopsy? % of all autopsies in UK
Hospital 10% , medico-legal 90%
Two types of medico-legal autopsies?
coronial (standard), forensic (deaths involving crime)
What are hospital autopsies used for?
teaching, research, governance
Types of death referred to coroners?
- Presumed natural (cause of death not known)
- Presumed iatrogenic (anaesthetic deaths, abortion, etc.)
- Presumed unnatural (accidents, suicide, neglect, unlawful killing, etc.)
Who refers death to coroners?
Doctors (GMC guidance, no statutory duty), registrar of BDM, relatives, police
Laws related to autopsies?
Coroners Act 1988, Coroners Rules 1984, Amendment Rules 2005, Coroners and Justice Act 2009, Human Tissue Act 2004
Define inflammation
the local physiological response to tissue injury
Benefits of inflammation?
destruction of invading microorganisms, walling off an abscess cavity (thus preventing the spread of infection)
Problems of inflammation?
- an abscess in the brain would lead to compression of vital surrounding structures
- fibrosis resulting from chronic inflammation may distort tissues and alter their function
5 different cells involved in inflammation?
neutrophil polymorphs, macrophages, lymphocytes, endothelial cells, fibroblasts
What is acute inflammation?
initial and often transient series of tissue reactions to injury
Acute inflammation steps (I’VE NO Really Sick Opening Pick-ups)
Initial reaction to tissue injury
Vascular component - dilation of vessels
Exudative component - vascular leakage of protein-rich fluid
Neutrophil polymorph - characteristic cell recruited to the tissue
Outcome(s)- (1) Resolution, (2) Suppuration (pus formation), (3) Organisation (tissue replacement by granulation tissue), (4) Progression to chronic inflammation
Causes of acute inflammation (My Hairy Backside Cannot Poo Today)
Microbial infections Hypersensitivity reactions Bacterial toxins Chemicals Physical agents (e.g. trauma, radiation) Tissue necrosis
Signs of acute inflammation? (Some People Really Hate Leicester)
Swelling (tumor) Pain (dolor) Redness (rubor) Heat (calor) Loss of function
Chemical mediators of acute inflammation inducing pain?
Bradykinin, prostaglandins, serotonin
In the early stages of acute inflammation, what accumulates in the extracellular spaces of damaged tissue?
Oedema fluid, fibrin, neutrophil polymorphs
Acute inflammation involves which 3 response processes?
- Vessels get wider, increased flow
- Increased vascular permeability and formation of fluid exudate
- Formation of cellular exudate, emigration of neutrophil polymorphs into the extravascular space
Diagnostic histological feature of acute inflammation?
Accumulation of neutrophil polymorphs in the extracellular space
Chemical mediators in acute inflammation?
Histamine, serotonin, prostaglandins
Large source of histamine in acute inflammation?
Mast cells
Define chronic inflammation?
subsequent and prolonged tissue reactions to injury following the initial response
4 causes of chronic inflammation?
- primary chronic inflammation
- transplant rejection
- progression from acute inflammation
- recurrent episodes of acute inflammation
What are granulomas?
Collection of macrophages, structure found during inflammation
granulation tissue?
important component of healing and comprises small blood vessels in a connective tissue matrix with myofibroblasts
In chronic inflammation what type of cells are typically in the cellular infiltrate?
Lymphocytes, plasma cells, macrophages
Most common form of granuloma?
tuberculosis
What is lobar pneumonia?
affects a lobe of the lung rather than the whole thing, characterised by inflammatory exudate (neutrophil polymorphs) within the intra-alveolar space (Streptococcus pneumoniae)
What is granulation tissue?
New connective tissue and microscopic blood vessels that form on the surfaces of wounds during the healing process (combination of myofibroblasts and capillary loops)
define organisation?
repair of specialised tissues by the formation of a fibrous scar
What is wound contraction?
reduces the volume of tissue repair due to contraction of myofibroblasts
Incised skin wounds - healing by 1st intention
- Incision (e.g. by surgical scalpel) causes minimal tissue damage either side of cut
- Blood vessels occluded by thrombosis
- Exudation of fibrinogen, forms weak fibrin join to bind two sides
- Collagen synthesis and epidermal re-growth
Tissue loss - healing by 2nd intention
A tissue loss injury/ other reason meaning the wound margins are not aligned, requiring another mechanism for repair:
- Loss of tissue, formation of granulation tissue
- Organisation - early fibrous scar
- Scar contraction
- Phagocytosis to remove any debris
- Granulation tissue fills in defects
- Epithelial regeneration to cover surface
Cells that regenerate?
hepatocytes, pneumocytes, all blood cells, gut epithelium, skin epithelium, osteocytes
Cells that DON’T regenerate?
myocardial cells, neurones
Repair - when tissue is damaged and unable to…? Damaged tissue is replaced by…? examples?
Regenerate, fibrous tissue, heart after myocardial infarction, spinal cord after trauma
Cell renewal
- Labile cells - good capacity to regenerate, e.g. surface epithelial cells
- Stable cell populations - divide at slow rate, e.g. hepatocytes
- Permanent cells - no regeneration, e.g. nerve cells
- Stem cells
Hepatocytes have excellent regenerative capacity, they are part of which cell population?
Stable
Define thrombosis
solidification of blood contents that forms WITHIN the vascular system during LIFE
How is a CLOT different from thrombosis? A clot is
Blood coagulated OUTSIDE the vascular system or after DEATH
Why doesn’t thrombosis occur all the time? (2)
- Laminar flow - cells travel in the centre of vessels
2. Endothelial cells (healthy) are not ‘sticky’
Platelets are derived from cells in the bone marrow called?
megakaryocytes
Granules within platelets?
Alpha - structural components e.g. fibrinogen
Electron dense - e.g. ADP, TxA2 which cause platelets to aggregate
When are platelets activated and subsequently release the contents of their granules?
When they come into contact with exposed collagen in the damaged endothelium
Shape change of platelets?
Smooth discoid –> spiculated, develop pseudopodia
Action of TxA2 in platelet aggregation?
Stimulates platelet binding and causes contraction of action and myosin to condense aggregation
Platelets bind to collagen via?
vWF
Thrombosis may be caused by 3 factors?
- Changes in vessel wall
- Changes in blood flow
- Changes in blood constitutents
How do lose does of aspirin inhibit thrombosis?
Inhibit COX-1 enzyme which is required for the formation of thromboxane A2 which stimulates platelet aggregation
Atheroma?
degeneration of the walls of the arteries caused by accumulated fatty deposits and scar tissue, thus leading to restricted circulation and risk of thrombosis
Where do most venous thrombi begin? Why?
Valves, induce a degree of turbulence
Why does immobilisation increase the risk of deep vein thrombosis?
Venous return from the legs is very reliant upon calf and muscle contraction and relaxation
How does warfarin prevent clot formation (in severe cases)?
Blocks the liver from using vitamin K to produce clotting factors (inhibits vitamin K epoxide reductase complex 1 which activates vitamin K int he body)
What is an embolus?
Mass material in the vascular system able to lodge in a vessel and block the lumen (usually caused by part of a thrombus that has broken off)
What is meant by embolism?
The process of a solid mass in the blood being carried through the circulation to a place where it gets stuck and blocks the vessel
Venous embolism –> pulmonary embolism?
If an embolus enters the venous system it will enter the R atrium via the vena cava and will lodge somewhere in the pulmonary arteries resulting in a pulmonary embolism
Why can’t a pulmonary embolism –> arterial circulation?
Vessels in the lung split down to capillary size, thus the lungs act as a filter for any venous emboli
Ischaemia?
Reduction of blood flow to a tissue without any other implications
Infarction?
reduction of blood flow to a tissue that is so reduced that it cannot even support mere maintenance of the cells in the tissue so they die