Pathology Flashcards
Define inflammation
A reaction to injury or infection involving cells such as neutrophils and macrophages
How can inflammation be described as good or bad?
Good: in response to injury or infection
Bad: autoimmunity, over-reaction to stimulus
What is the difference between acute and chronic inflammation
Acute = sudden onset, short duration, usually resolves, lots of neutrophils
Chronic = slow onset or sequel to acute, long duration, may never resolve, lots of macrophages/lymphocytes
List 5 cells involved in inflammation
Neutrophils
Macrophages
Lymphocytes
Endothelial cells
Fibroblasts
How are neutrophils involved in inflammation?
These cells are first on scene, but short-lived and usually die at the scene
Their cytoplasmic granules of enzymes kill bacteria
They also release chemicals to attract other inflammatory cells (macrophages)
How are macrophages involved in inflammation?
These cells are long-lived, surviving for weeks-months
They have phagocytic properties, so ingest bacteria and debris
They may present the antigen to lymphocytes
How are lymphocytes involved in inflammation?
These are long lived cells which survive for years
They produce chemicals which attract other inflammatory cells
They contribute to the immunological memory to past infections/antigens
Specialised lymphocytes called plasma cells produce antibodies
How are endothelial cells involved in inflammation?
These cells become sticky (produce nitrous oxide) in areas or inflammation so inflammatory cells adhere
They become porous to allow inflammatory cells to pass into tissues (fluid leakage causes swelling)
They grow into areas of damage to form new capillary vessels
How are fibroblasts involved in inflammation?
These are long lived cells
They form collagen in areas of chronic inflammation and repair
Define granuloma
A pattern of chronic inflammation, consisting of a cluster of macrophages surrounded by lymphocytes, seen in Crohn’s disease and sarcoidosis
When and where does tissue regeneration occur?
When the initiating factor is removed, and where the tissue is undamaged and able to regenerate
Which cells are able to regenerate
Hepatocytes
Pneumocytes
Blood cells
Gut epithelium
Skin epithelium
Osteocytes
When and where does tissue repair occur?
When the initiating factor is still present, and where the tissue is damaged and unable to regenerate
Give examples of where repair takes place
Heart after myocardial infarction
Brain after cerebral infarction
Spinal cord after trauma
In repair, what is damaged tissue replaced by?
Fibrous tissue (collagen) from fibroblasts
In skin wounds, what is healing by 1st intentions?
When the edges of the wound are brought together by sutures
The wound will be bridged by fibrin, collagen forms, and the epithelium regenerates
There will be a smaller scar and faster healing
In skin wounds, what is healing by 2nd intention?
When the edges cannot be / are not brought together
The wound can’t be bridged by fibrin or collagen, so the wound heals from the bottom into the space, with the gap being restored by scar tissue
There will be a larger/more visible scar
Define thrombosis
A solid mass of blood constituents formed within an intact vascular system
Describe the process of thrombosis
- Normal blood flows consistently through the centre of the vessel in laminar flow
- Exposed collagen from endothelium damage causes platelets to stick to the side of the vessel (because nitrous oxide production is stopped)
- Platelets release activating factor which attracts others (positive feedback)
- The blood flow becomes more turbulent and red blood cells also become trapped
- A thrombus forms due to the presence of clotting precursors and fibrin deposition
What are the three causes of thrombosis?
Change in blood flow (laminar -> turbulent)
Change in vessel wall (endothelial damage e.g. from smoking, diabetes etc.)
Change in blood constituents (e.g. abnormal clotting factors)
What is stasis?
A cause of thrombosis in veins due to the blood flow being slower
How is thrombosis prevented?
Low-dose aspirin (inhibits platelet aggregation by irreversibly inhibiting platelet cyclo-oxygenase, no positive feedback loop)
Define embolus
A mass of material in the vascular system which is able to become lodged within a vessel and block it
Give some examples of emboli
Deep vein thrombosis breaks off and becomes lodged in the smaller vessels of the lungs, causing pulmonary embolism
Endocarditis causes material to break off and cause septic emboli, which can become lodged in the liver or lungs
IV drug users are injected emboli into their blood vessels
Define ischemia
A reduction in blood flow
When/where does ischemia occur?
Most commonly in cells which are further away from the vessel, so are receiving less oxygen
The cells are still alive, but poorly/not functioning
Define infarct
A reduction of blood flow (ischemia) with subsequent cell death
When/where does infarction happen?
Occurs in organs with only one blood supply (end artery supply)
A thrombus/embolus blocks off the entire supply to the organ, leading to infarct/death
What are the 5 cardinal signs of inflammation
Redness
Swelling
Heat
Pian
Loss of function
Describe the time course of atherosclerosis and the change in structure
Increases with age (steep increase at 40/50)
- fatty streaks present at younger ages (early stages, mainly inflammatory cells)
- then intermediate lesions (involvement of muscle cells, T lymphocytes, platelets)
- established atherosclerosis at older ages (fibrous plaques/advanced lesions, covered by fibrous cap, prone to rupture)
- plaque rupture (balance shifts in favour of inflammation, cap becomes weak, leads to thrombus and vessel occlusion
Describe the distribution of atherosclerosis
Only in high pressure arteries
- found within peripheral and coronary arteries
- common in aorta
- changes in flow/turbulence (e.g. bifurcations) cause artery to alter endothelial cell function and wall thickness (neointima)
- never in low pressure systems like pulmonary arteries
List the constituents of an atherosclerotic plaque
Fibrous tissue (forms the cap)
Lipid deposits
Cholesterol
T lymphocytes
Macrophages
List some risk factors for atherosclerosis
Modifiable…
Smoking
Weight (obesity)
Lack of exercise
Diet (high serum cholesterol)
Non-modifiable…
Age
Gender
Ethnicity
Family history
Genetic causes of increased weight/hyperlipidaemia/diabetes
List some complications of atherosclerosis
Cerebral infarction
Myocardial infarction, cardiac failure
Carotid atheroma (emboli causes TIA/stroke)
Aortic aneurysm (rupture -> sudden death)
Peripheral vascular disease