二.Increased vascularpermeabilityIncreased permeability the most important causeresulting in exudation of fluid and protein(一)MechanismofIncreasedpermeability1. EC retraction :Formation of endothelialgapsin venulesImmediatetransientresponseCytoskeletalreorganization
二 . Increased vascular permeability Increased permeability →the most important cause resulting in exudation of fluid and protein (一)Mechanism of Increased permeability 1. EC retraction : Formation of endothelial gaps in venules Immediate transient response Cytoskeletal reorganization
DReceptor to the mediator invenularEC:histamine,bradykinin,substance P,leukotriene2)Cytoskeletalreorganization:induced by IL-1, TNF , hypoxia2. Increased transcytosis:By transcytoplasmic channelVEGF,histamine, bradykinin,Increasing the number and the size of channels
1) Receptor to the mediator in venular EC: histamine, bradykinin, substance P, leukotriene 2) Cytoskeletal reorganization: induced by IL-1, TNF , hypoxia 2. Increased transcytosis: By transcytoplasmic channel VEGF , histamine, bradykinin, Increasing the number and the size of channels
3.Direct endothelial injuryImmediatesustainedresponse:severe burn,purulent Bacresult in EC necrosis and detachmentleakage starts immediately after injurysustained at a high level for several hoursuntil damaged BV thrombosis and repaired
3. Direct endothelial injury Immediate sustained response: severe burn, purulent Bac result in EC necrosis and detachment leakage starts immediately after injury sustained at a high level for several hours until damaged BV thrombosis and repaired
4.DelayedprolongedleakageMild-to-moderate thermal injury, toxin, X-rayincreased permeability after a delay of2to 12hourslasting for several hours or daysinvolves venules as well as caps5. Leukocyte-mediated endothelial injuryLeukocyte adhere to EC activatedReleasing toxic species and proteolyticenzymes
4. Delayed prolonged leakage Mild-to-moderate thermal injury, toxin, x-ray increased permeability after a delay of 2 to 12 hours lasting for several hours or days involves venules as well as caps 5. Leukocyte-mediated endothelial injury Leukocyte adhere to EC activated Releasing toxic species and proteolytic enzymes
6. High permeability of new caps:Newvessels sprouts remain leaky until ECsdifferentiate and form intercellular junctions.Certain factors that cause angiogenesisVEGF)increasepermeabilityIncreased density ofreceptor for vasoactivemediators in the surface of EC
6. High permeability of new caps: ① New vessels sprouts remain leaky until ECs differentiate and form intercellular junctions. ② Certain factors that cause angiogenesis (VEGF) increase permeability ③ Increased density of receptor for vasoactive mediators in the surface of EC