Inflammation 1: Vascular changes & formation of cellular exudate Flashcards
Define inflammation
it’s the Dynamic response of any vascularised tissue agianst to tissue injury, to eliminate cause of cell injury & initiate repairing
local Vascular reaction/ vascular change during inflammation is divided into
- Change in vascular Caliber (diameter) & flow
- Increase in Vascular permiability
Describe the changes of vascular Caliber & flow during vascular change of inflammation
- transient Vasoconstricition
-
Histamine released from damaged tissue causes:
* Ateriole vasodilatation —> Hyperemia
* redness (erythrema) & Hotness = Flare - Increase in hydrostatic pressure (fluid capillary permiability increases) so more fluid exits
- the exit of fluid causes increase in blood viscosity (thrombosis/ stasis)
- Formation of Exudate containing fluids & cells
Causes Increase in vascular permibaility during vascular change of inflammation
- histamine & Bradykinin causes contraction & shortening of endothelial cells & forming intracellular gaps
- Endothelial cellular damage during burns or some infections
Define exudate
fluid rich in protein which moves into extravascular tissue
Describe how exudate moves into extravascular tissue
- It’s protein rich, meaning it has increased osmotic presure favoring movoment outside, so it moves down osmotic gradient
- The increased hydrostatic pressure caused the vasodilatation
Enumerate benefits of Exudate/ inflammatory edema
- Dilutes any toxins
- Facilitate the entry of antibodies (lysis or opsonization)
- Transportation of antibiotics to infected site
- transportation of Fibrin to the site of injury/ infection:
* trap organisms & facilitate phagocytosis
* Matrix for healing - deliver oxygen & Nutreints
Formation of cellular Exudate is divded into
- Recruitement of Leukocytes (WBC)
- Activation of Leukocytes
Steps of Leukocyte recruitment
- Margination
- Rolling
- Pavementation
- Emigration/migration/infiltration
- Chemotaxis
Define margination of leukocytes
the Neutrophils will flow from laminar blood flow to plasmatic zone due to loss of intravascular fluid (increased stasis & viscosity)
which receptors are responsible for the rolling of leukocytes
Selectin P & E receptors
Which receptors are responsible for the pavementation of leukocyes onto endothelium after rolling
Integrins
describe attachement and rolling of leukocytes onto endothelium
- After reaching plasmatic zone, leukocytes attach to sticky enothelium by P & E selectin receptors
- they continue to detach and attach, causing them to tumble onto endothelial surface
describe pavementation of leukocytes onto endothelium
tight adhesion of neutrophils to vascular endothelium by integrins
mechanism of integrins
they are present on the WBC, they attach to their ligands that are present on the endothelial wall
Describe Emigration, migration & infiltration of Leukocytes
Leukocytes squeeze themselves through widened endothelial spaces (mainly of venules) by pseudopodia by amoeboid movement driven by cytokines
- they release collagenase to be able to digest and pass through basement membrane
Define Chemotaxis & explain its mechanism
The movement of Leukocytes towards the site of injury via chemical attractor/chemostatic substances, they do that by:
1. reacting on receptor of Leukocyte from the direction of the injury
2. this causes assembly of cytoskeleton contractile elements forming pseudopods facing direction of injury
3. pseudopods anchor to ECM to the pull the cell in the direction of the extension
Enumerate chemotactic factors
- Exogenous (lipids & peptides of baterial products)
- C3a & C5: complement system from plasma
- IL8 (interleukin 8): cytokines of chemokine family produced by cells
- LB4 (leukotriene B4): from arachidonic acid
Define Luekocyte activation/ phagocytosis
Attachement of recongition particles to ingesting leukocytes, causing them to ingulf & kill organisms & degrade the ingested material
Enumerate Opsonins
- IgG
- C3b
define opsonisation
the process of which opsonins coat organisms to make them a target for phagocytosis
describe engulfing mechanism
Luekocytes surround bacteria by pseudopodia & engulf them by endocytosis inside vacuoles called phagosomes
* Inside the leukocyte, phagosomes bind with lysosomes to form phagolysosomes
describe killing & degenration of bacteria done by leukocytes
- By oxygen dependent mechanism (ROS) or oxygen independent (acidic pH)
- after bacteria is dead and broken down, chemical mediators are released (arachidonic acid metabolites & cytokines) causing more recruitement of WBCs
- finally, moncytes (macrophages) arrive at the site
role of Macrophages in acute inflammaiton
- do not predominate until later stages
- play lesser role in phagocytesis compared to neutrophils
- clean tissue debris and damaged cells
- digest inflmmatory exudate and drain them in lymphatics
- secrete growth factor for repair
Final fate of exudate
to be digest by macrophages (monocytes) and drained into lymphatics
