Pathology Flashcards
Define inflammation.
The body’s response to injury or infection using different cells.
Define acute inflammation.
Neutrophil-mediated inflammation.
Sudden onset, short duration, usually resolves.
Give 6 causes of acute inflammation.
- Microbial infections (most common)
- Chemicals
- Physical agents
- Hypersensitivity reactions
- Bacterial toxins
- Tissue necrosis
Describe how microbial infections cause acute inflammation.
Viruses: cell death due to intracellular multiplication.
Bacteria: The release of exotoxins (involved in the initiation of inflammation) or endotoxins.
Describe how chemicals cause acute inflammation.
Corrosive chemicals (acids, alkalis, oxidising agents) cause inflammation through gross tissue damage.
Infecting agents may release specific chemical irritants that lead to inflammation.
Describe how physical agents cause acute inflammation.
Tissue damage as a result of physical trauma, UV, ionising radiation, burns or excessive cooling (frostbite).
Describe how hypersensitivity reactions cause acute inflammation.
An altered state of immunological responsiveness causes an inappropriate or excessive immune reaction, damaging tissues.
The types of reactions all have cellular or chemical mediators similar to those involved in inflammation.
Describe how tissue necrosis causes acute inflammation.
Death of tissues from lack of oxygen or nutrients resulting from inadequate blood flow (infarct) is a potent inflammatory stimulus.
Describe chronic inflammation.
Macrophage/lymphocyte-mediated inflammation.
What are neutrophil polymorphs?
White blood cells produced in the bone marrow, they have a very short lifespan (2 or 3 days).
They have a polylobed nucleus, hence the name ‘polymorph’.
What is the function of neutrophil polymorphs?
Phagocytosis of debris and bacteria.
Release of lysosomes which digest phagocytosed bacteria.
What are macrophages?
White blood cells with longer lifespans than neutrophils (months to years).
What is the function of macrophages?
Phagocytosis of debris and bacteria.
Transportation of material to lymph nodes and lymphocytes to induce a secondary immune reaction.
What are macrophages called in the liver, bone and brain respectively?
Kupffer cells (liver)
Osteoclasts (bone)
Microglial cells (brain)
What are lymphocytes?
Long-lived white blood cells (years).
What is the function of lymphocytes?
Producing chemicals involved in controlling inflammation.
Production of antibodies from B lymphocyte plasma cells (immunological memory).
What are fibroblasts?
Cells which produce collagenous connective tissue in scarring following certain types of inflammation.
Describe the sequence of acute inflammation.
- Injury or infection
- Neutrophils arrive and phagocytose and release enzymes
- Macrophages arrive and phagocytose
- Either resolution (with clearance of inflammation) or progression (chronic inflammation)
Give 3 examples of acute inflammation.
Acute appendicitis, physical trauma, streptococcal sore throat.
Describe the sequence of chronic inflammation.
- Either progression from acute inflammation or starts as ‘chronic’ inflammation (eg. infectious mononucleosis)
- No or very few neutrophils
- Macrophages and lymphocytes arrive, then fibroblasts
- Can resolve if no tissue damage (eg. glandular fever) but often results in repair and formation of scar tissue
Give 3 examples of chronic inflammation.
Tuberculosis, Crohn’s disease, rheumatoid arthritis.
What are granulomas?
An aggregate of epithelioid histiocytes (derivatives of activated macrophages resembling epithelial cells).
These cells secrete ACE (a blood marker of someone who has granulomatosis disease eg. TB, leprosy and Crohn’s)
Describe the systemic effects of inflammation.
- Pyrexia
- Weight loss
- Reactive hyperplasia of the reticuloendothelial system
- Haematological changes
- Amyloidosis
What is reactive hyperplasia of the reticuloendothelial system?
Hyperplasia of the reticuloendothelial system (RES), which removes immune complexes from the circulation in healthy persons.
The RES is formed of monocytes of the blood, macrophages in connective tissue, lymphoid organs, bone marrow, liver and lung.