inflammation Flashcards
what is inflammation?
it is the **reaction **of vascularised living tissue to a local injury
what is the suffix associated with inflammation?
ITIS
eg appendicitis, bronchitis
what are examples of causes of inflammation?
- infectious agents - eg viruses, bacteria, fungi
- tissue necrosis
- foreign bodies
- immune reactions - hypersensitivity reactions - endogenous (autoimmune) or exogenous agents - eg allergy
what are 3 objectives of inflammation?
- **localise and eliminate **the causative agent
- limit tissue injury
- begin the **process of repair **
what are 5 classic signs of acute inflammation?
- heat
- redness
- swelling
- pain
- loss of function
define** acute vs chronic inflammation**
- acute - immediate and early response to injury, devekops rapidly and resolves rapidly
- **chronic **- longstanding inflammation, primary or following an acute inflammation
what is acute inflammation characteristed by?
- accumulation of fluid, protein and acute inflammatory cells at the site of injury
what are the main cells involved in acute inflammation?
neutrophils
what are the ‘mediators’ of acute inflammation?
- chemical products derived from the plasma or produced by cells
- they initiate the inflammation process - & cause vasodilation of vessels
what are the** vascular events** that take place in acute inflammation?
- vasodilatation of blood vessels - which leads to **increased blood flow and increased hydrostatic pressure** - redness and heat symptoms
- vessels become more permeable or ‘leaky’ - exudate protein rich fluid - leads to swelling
- both of the above lead to increased blood viscosity (intrinsic factor of blood)
- wbc’s accumulate against the inner layer of vessel wall
what is oedema?
excess fluid in the interstitial tissue or body cavities
what is pus?
purulent inflammatory exudate rich in neutrophils and cell debris
what is exudate?
fluid that leaks out of blood vessels into nearby tissues
describe the **margination, rolling & transmigration ** in the cellular events that occur in acute inflammation
- with** vasodilatation and increased vascular permeability,** fluid & plasma proteins will leak out of the vessel - which will lead to stasis and **wbc’s will accumulate **against the vessel wall
- wbc’s will then** roll against the vessel wall** and** transmigrate** through the vessel and into the surrounding tissue
apart from migration, rolling, transmigration and migration to site of injury, what other cellular events occur in acute inflamation?
- phagocytosis - cells engulf bacteria etc
- cells release enzymes and other products if necessary
what are the main cells involved in acute inflammation & what to they do ?
- white blood cells - esp **neutrophils and macrophages **are recruited to site of injury - they recognise pathogens and debris
- they eliminate them and produce growth factors to allow for repair
what are the** beneficial effects** of inflammation?
- toxins are diluted
- fibrin is produced - which delays bacterial spread
- antibodies arrive to site of injury
- destruction of microbial agent
- delivery of nutrients and o2 - due to vasodilation
- removal of tissue debris
what are the **harmful effects **of inflammation?
- can impair blood flow
- can cause mechanical effects - eg swelling of epiglottis in throat
- impaired function
- can destruct tissue
what are the systemic effects of inflammation?
- pyrexia - fever
- increased tendency to sleep
- pain
what can be seen in the laboratory about the systemic effects of inflammation?
- leucocytosis - increased wbc’s
- anaemia - if there is blood loss
- acute reactive proteins - c reactive proteins
what are the main outcomes of acute inflammation?
- complete resolution
- absess formation - rare - occurs if there is not complete removal
- healing by connective tissue replacement - fibrosis
what is chronic inflammation?
- prolonged inflammation - for weeks or even months
why do people get chronic inflammation?
- persistent or repeated bouts of acute inflammation
- prolonged normal healing
what are some examples of the causes of chronic inflammation?
- persistent infection - eg bacilli bacteria or viruses
- hypersensitivity - may be autoimmune, or abnormal response to normal host flora
- exposure to potentially toxic substances - may be exogenous eg silica or endogenous eg lipids
what are the main features of chronic inflammation?
- infiltration or presence of inflammatory cells - macrophages, lymphocytes and plasma cells
- tissue destruction - due to persistent injury
- repair - attempt at healing by connective tissue replacement
what are the main effector cells in chronic inflammation?
macrophages
what is the function of macrophages?
- sense and engulf particles
- induce an inflammatory response
what important cells do macrophages activate?
lymphocytes
what is granulomatous inflammation?
* special type of chronic inflammation that is characterised by nodular aggregrates of macrophgaes and multinucleated giant cells
what are examples of things that may lead to granulomatous inflammation?
- infections - eg tb or fungal infections
- foreign body - will trigger ongoing response
- tumours
define healing
the replacement of destroyed or lost tissue by a viable (usable) tissue
what is the initial response of damaged tissue to injury?
acute inflammation
what is complete resolution?
regeneration through proliferation of adjacent surving structures and tissue stem cells
what is fibrosis ?
- fibro proliterative response
- scarring
does the healing process usually involve regenration or scarring?
- usually a combination of both
- does depend on .. ability of body to remove cauative agent, ability to clear the inflammatory debris, ability of cells to regenerate and the degree of architectural damage
what are liable cells?
- they are continuously dividing cells
- examples - epithelial cells such as skin, oral cavity and GIT
what process occurs after injury to liable cells?
regeneration - if the supporting stroma is intact
what are stable cells?
- cells that have a low level of replication
- example - liver
- they can be stimulated to divide
what process occurs after injury to stable cells?
- healing by regeneration - if the supporting stroma is intact
what are permanent cells?
- non dividing cells
- eg neurons and myocardial cells
what process occurs after injury to permanent cells?
- NO REGENERATION
- replaced by connctive tissue - and healing by fibrosis
Describe regeneration
- replacement of lost cells by cells of the same type through cell division
- however - the supporting framework must still be intact
- tissue is returned to its pre injury state
- controlled by stimulatory and inhibitory factors
describe **fibrosis **
- fibroproliferative response that patches rather than restores the tissue
- occurs when there is destruction to both functional cells and stromal cells, death of permanent cells and long standing inflammation
what are the 3 phases of healing?
- inflammatory phase
- proliferative phase
- remodelling phase
What does the inflammatory phase of healing involve?
- haematoma formation - injury to blood vessel
- presence of neutrophils
- presence of macrophages
- removal of tissue debris
what does the proliferative phase of healing involve?
- epithelial cell proliferation - granulation tissue forms
- proliferation of fibroblasts and new vessel formation
what does the remodelling phase of healing involve?
- replacement of the granulation tissue by a fibrous stroma
- degradation of excessive extra cellular matrix by metalloproteinase
- increase in the strength of the wound
what are the 2 types of wound healing on the skin?
- primary intention
- secondary intention
describe primary intention
- used in small wounds where the edges are close together
- where there is minimal loss of tissue
- eg after a surgical incision or clean wound
describe secondary intention
- for large gaping wounds
- where there is an extensive loss of cells
Describe the stages of wound healing by primary intention - day 1-7
- day 1 - wound filled with blood clot and there is acute inflammation in surrounding tissue
- day 2 - macrophages come and the epithelial cells start to close the wound by proliferating on the surface
- day 3 - granulation tissue formation
- day 5 - collagen deposition
- day 7- sutures removed
how is wound healing by secondary intention different to primary intention?
- process is similar
- slower - as there is a much larger wound
- more intense inflammatory reaction
- more scarring
by what process does healing occur in skeletal muscle ?
regeneration
what are examples of local factors that influence healing?
- infections
- forgein bodies
- type of tissue
- size and location
what are systemic factors that can affect healing?
- age and nutrition
- hormones
- chemotherapy etc
what are the 4 stages of bone healing?
- haematoma formation
- external callus bridges the fracture site outside the bone
- internal callus bridges the fracture in medullary cavity
- remodelling
