Inflammation Flashcards
inflammation
Inflammation is the reaction of a vascularised living tissue to a local injury
how are inflammation lesions typically indicated
by suffix (ITIS -> appendicitis, bronchitis)
causes of inflammation
• Infectious agents • Tissue necrosis • Foreign bodies • Immune reactions (hypersensitivity responses) • Endogenous • Exogenous
objectives of inflammation
- Localise and eliminate the causative
agent - Limit tissue injury
- Begin the process of repair
5 classic local signs of acute inflammation
- Calor - Heat
- Rubor - Redness
- Tumor - Swelling
- Dolor - Pain
- Functio laesa – loss of function
difference between acute and chronic inflammation
acute - immediate and rapid response but resolves just as fast
chronic - longstanding, primary or followed after acute inflammation
onset differences of acute and chronic inflammation
acute - fast (minutes - hours)
chronic - slow (days)
cellular infiltrate difference between acute and chronic swelling
acute - mainly neutrophils
chronic - monocytes/macrophages and lymphocytes
the difference in the extent of tissue injury and fibrosis in acute an chronic inflammation
acute - Usually mild and self limited
chronic - Often severe and
progressive
difference in local and system signs between acute and chronic inflammation
acute - Prominent
chronic - less
how is acute inflammation characterised
accumulation of fluid, protein and acute inflammatory cells at the site of injury
what white blood cells are the main cells in acute inflammation
neutrophils
what is acute inflammation mediated by
chemical products which cause dilatation of the
vessels & start inflammatory process derived from plasma
vascular events of acute inflammation
• Vasodilatation – increased blood flow
• Increased vascular permeability
– permitting plasma proteins and white blood cells to leave the circulation
cellular events in acute inflammation
Accumulation and activation at the site of the injury – main inflammatory cell
-> neutrophil
vascular changes in acute inflammation
vasodilation - small blood vessels, inc. blood flow and hydrostatic pressure -> redness + heat
more permeable - ooze of protein rich fluid -> swelling
oedema
pus
describe pus
purulent inflammatory exudate rich in neutrophils and
cell debris
cells in acute inflammation
white blood cells - especially neutrophils and macrophages
what white blood cells respond to bacteria
neutrophils
what white blood cells respond to viruses
lymphocytes
what white blood cells respond to allergies/hypersensitivity
eosinophils
beneficial effects of inflammation
- Dilution of toxins
- Fibrin production delays bacterial spread
- Arrival of antibodies to the site of inflammation
- Destruction of microbial agent
- Drug transport
harmful effects of inflammation
- Mechanical effect e.g. epiglottitis
- Impaired flow e.g. acute meningitis
- Impaired function
- Tissue destruction
systemic effects of inflammation - clinical
- Pyrexia
- Increased tendency to sleep
- Constitutional symptoms
- Pain
- Lymphadenopathy and splenomegal
systemic effects of inflammation - laboratory
leucocytosis
raised ESR
Anaemia
acute reactive proteins - c -reactive protein
outcomes of acute inflammation
complete resolution
abscess formation
healing by connective tissue replacement (fibrosis) after substantial tissue destruction
progression to chronic inflamamtion
what causes chronic inflammation
• Acute inflammation – prolonged normal
healing
• Persistence/repeated bouts of acute inflammation
• Low grade, smouldering
persistent infection - rubercle, bacilli, viruses
hypersensitivity
exposure to potentially toxic subtances
abscess
a walled off collection of pus
what are the main effector cells of chronic inflammation
macrophages - sense and engulf particles
induce inflammatory response
function of lymphocytes in chronic inflammation
activated by macrophages and activate other inflammatory cells
granulomatous inflammation
• Specific form of chronic inflammation characterised
by nodular aggregates of macrophages and giant cells
examples of granulomatous inflammation
infection - TB, Fungi
unknown aeitology of what granulomatous inflammation
sarcoidosis
crohn’s disease
initial response of a damaged tissue
acute inflammation
leads to complete resolution and fibrosis
complete resolution
• Regeneration – through proliferation of adjacent surviving structures and tissue stem cells
fibrosis
• Fibro proliferative response -> scar
• Resolution of inflammation ->
organisation
healing process
regeneration and scar remove causative agent clear inflammatory debris architectural damage chronicity of associated inflammation
labile cells
• Continuously dividing cells
• Epithelial cells such as skin, oral cavity and GIT
• Injury to such tissue can easily heal by regeneration if the
supporting stroma is intact
stable cells
- Normally low level of replication
- Liver cells
- Cells can be stimulated to divide
- Healing by regeneration if the supporting stroma is intact
permanent cells
- Non dividing cells
- Neurons
- Myocardial cells
- No regeneration
- Replaced by connective tissue healing by fibrosis
regeneration
• Replacement of lost cells by cells of the same type through cell division to return to its pre-injury state
how is regeneration controlled
by stimulatory and inhibitory factors and interactions between
cells and extra-cellular matrix (supporting
framework)
what must be in order for regeneration to occur
The supporting framework must be intact
function of fibrosis
to help with limited restorative capacity -fibroproliferative response that ‘patches’ rather than restores the tissue
when does fibrosis occur
- Destruction to both functional
(parenchymal) cells and stromal framework - Death of permanent cells
- Long-standing inflammation
phases of healing
- Inflammatory phase
- Proliferative phase
- Remodelling phase
inflammatory phase
- Haematoma formation
- Infiltration by neutrophils
- Infiltration by macrophages
- Removal of tissue debris
proliferative phase
• Epithelial cell proliferation
• Proliferation of fibroblasts and new vessels formation
(granulation tissue)
matrix remodelling
- Replacement of the granulation tissue by a fibrous stroma (scaffold)
- Degradation of excessive extra-cellular matrix by metalloproteinase
purpose of matrix remodelling phase of healing
• Increase in the strength of the wound
types of wound healing on the skin
primary intention
secondary intention
primary intention
- Wound with apposed edges
- Minimal loss of tissue
- Surgical incision or clean wound
secondary intention
- Large gaping wound
- Extensive loss of cells
- Infarction
- Ulcer
- Abscess
stages of wound healing by primary intention in Day 1
• Wound filled with blood clot
• Acute inflammation in the surrounding
tissue
• Proliferation of epithelial cells
stages of wound healing by primary intention in Day 2
- Macrophages
* Epithelial cells start to close the wound by proliferating on the surface
stages of wound healing by primary intention Day 3
• Granulation tissue formation
stages of wound healing by primary intention Day 5
collagen deposition
stages of wound healing by primary intention Day 7
sutures removed
what is the wound strength after sutures are removed in 1 week
only 10% of unwounded
skin
what is the wound strength after 3-4 months
wound strength is about
80% of unwounded skin
what is the difference between wound healing by secondary intention
similar but; Slower • The inflammatory reaction is more intense • Wound contraction (myofibroblast) • More scarring
pathologic aspects of wound healing
- Deficient scar formation
- Wound rupture/ulceration • Excessive scar formation
- Contracture deformity
examples of excessive scar formation
hypertrophic scar
keloid scar
hypertrophic scar
raised, due to excessive collagen formation
keloid scar
extends beyond the original area of injury
cause of contracture deformity
Excessive wound contraction
producing claw deformities / limit joint
mobility
examples of healing in mucosal surfaces
- Erosion is healed by regeneration
* Ulceration by regeneration and fibrosis
examples of healing in liver
- A single short lived injury is healed by regeneration
* Chronic injury by cirrhosis
examples of healing in muscle
- Cardiac muscle -> Fibrosis
* Skeletal muscle -> Regeneration
examples of healing in nervous system
- Central nervous system -> Gliosis
* Peripheral nerves -> Regeneration
healing of bone
- haematoma formation
- External callus bridges the fracture site outside the bone
- Internal callus bridges the fracture in the medullary cavity
- remodelling
factors that influence healing
- Local factors
* Systemic factors
local factors
- Infections
- Ischaemia
- Mechanical forces (motion/wound tension)
- Foreign bodies
- Type of tissue
- Size and location
systemic factors
- Age & Nutrition (protein, Vit C)
- Metabolic status (DM)
- Hormones (steroids)
- Malignancy, Chemotherapy, Radiotherapy