Intro to Clinical Sciences Flashcards
What is inflammation?
The local physiology response to tissue injury.
N.b. it is NOT a disease but instead usually a manifestation of disease
Discuss the benefits and limitations of inflammation
Benefits:
-Destruction of invading microorganisms and the walling off of an abscess cavity thereby preventing the spread of infection
Limitations:
- Disease e.g. an abscess in the brain will act as a space-occupying lesion COMPRESSING vital surrounding structures
- Fibrosis resulting from CHRONIC INFLAMMATION may distort tissues and permanently alter their function
What is acute inflammation?
The initial and often transient series of tissue reactions to injury which may last from a few hours to a few days
e.g. appendicitis
Describes the steps involved in acute inflammation
- Initial reaction of tissue to injury:
- Vascular component: dilation of vessels
- Exudative component: vascular leakage of protein rich fluid
- Neutrophil polymorph, the characteristic type of WBC that is recruited to the tissue
What are the 3 main outcomes of acute inflammation?
- Resolution - goes away
- Suppuration - pus formation e.g. abscess
- Organisation - fibrosis scar tissue formation
- Progression to chronic inflammation
Describe the ‘organisation’ outcome process from acute inflammation
- Involves healing by fibrosis (scar formation) when there is substantial damage to the CT framework and/or tissue lacks ability to regenerate specialised cells
- Firstly dead tissues and acute inflammatory exudate are removed from damaged areas by macrophages
- Defect becomes filled by the ingrowth of GRANULATION TISSUE, a specialised vascular CT
- Granulation tissue gradually produces collagen to form a fibrous (collagenous) scar –> this constitutes the process of repair
Name 6 causes of acute inflammation
- Microbial infections e.g. pyrogenic (pus causing) bacteria, viruses
- Hypersensitivity reactions e.g. parasites, tubercle bacilli
- Physical agents e.g. trauma, ionising radiation, heat, cold
- Chemicals e.g. corrosives, acids, alkalis, reducing agents
- Bacterial toxins
6, Tissues necrosis e.g. ischaemic infarction
How do microbial infections lead to acute inflammation?`
- Viruses lead to death of individual cells by intracellular multiplication
- Bacteria release specific ENDOTOXINS that they synthesis themselves, which specifically INITIATE inflammation and are associated with their cell walls
- Some organisms cause immunologically mediated inflammation through hypersensitivity reactions
e. g. Parasitic infections and tuberculous inflammation are instances where hypersensitivity is important
n.b. microbial infections are the MOST COMMON CAUSE
How do hypersensitivity reactions lead to AI?
- Occurs when an altered state of immunological responsiveness causes a inappropriate or excessive immune reaction that damages the tissues
- Hypersensitivity reactions have cellular or chemical mediators similar to those involved in inflammation
How do physical agents lead to AI?
- Physical trauma, UV or other ionising radiation, burns or frostbite cause tissue damage which leads to inflammation
How do irritant and corrosive chemicals lead to AI?
- Corrosive chemicals provoke inflammation through GROSS TISSUE DAMAGE
- Infecting agents may release specific chemical irritants that lead directly to inflammation
How does tissue necrosis lead to AI?
- Inadequate blood flow (INFARCTION)* causes a lack of oxygen and nutrients leading to death of tissues
- Potent inflammatory stimulus
- Edge of a recent infarction often shows an acute inflammatory response due to peptides released from dead tissue.
Describe the essential macroscopic appearances of AI?
- Redness - rubor
Due to dilation of small blood vessels within the damaged area e.g. in skin affected by sunburn, cellulitis due to bacterial infection or acute conjuctivitis - Heat - calor
Increased blood flow (hyperaemia) through the region resulting in vascular dilation and delivery of warm blood to the site
n.b. increase in temp only seen in peripheral parts of body e.g. skin
Systemic dever - Swelling - tumor
Caused by oedema fluid accumulation in the extravascular space –> fluid exudate
Physical mass of inflammatory cells that have migrated into the area
Formation of new CT contributes - Pain - dolor
Due to stretching and distortion of tissues due to inflammatory oedema, particularly from pus under pressure in an abscess cavity
Chemical mediators of AI e.g. bradykinin, prostaglandins, serotonin are known to induce pain - Loss of function
Movement of an inflamed area is consciously and reflexly inhibited by pain
Severe swelling may physically immobilise tissue
