Changes

# '''Momentary vasoconstriction'''  

# '''Momentary vasoconstriction'''  

#* Following contact with the irritant, there is momentary vasoconstriction of the blood vessels in the affected area.

#* Following contact with the irritant, there is momentary vasoconstriction of the blood vessels in the affected area and is reversed within minutes.

#* This is reversed within minutes.

# '''Dilation of the blood vessels'''

# '''Dilation of the blood vessels'''

#* Initially, dilation of the capillaries is caused by the release of chemical mediators.

#* Initially, dilation of the capillaries is caused by the release of chemical mediators. The arterioles then dilate under the influence of a local axon reflex, which gives rise to an initial acceleration of the blood flow to the area. This then later gives way to a slowing of blood flow, caused by alterations in vascular endothelial permeability and the filling of previously closed capillaries.

#* Arterioles then dilate under the influence of a local axon reflex.

#* This gives rise to an initial acceleration of the blood flow to the area.

#**  This later gives way to a slowing of blood flow, caused by alterations   in vascular endothelial permeability and the filling of previously   closed capillaries.

# '''[[Exudation of fluid]]'''

# '''[[Exudation of fluid]]'''

#* Follwing the slowing of blood flow and altered capillary permeability, a protein-rich fluid is exudated.

#* Following the slowing of blood flow and altered capillary permeability, a protein-rich fluid is exudated.

# '''Margination of leukocytes'''

# '''Margination of leukocytes'''

#* Circulating white blood cells are attracted to the altered endothelial surfaces.

#* Circulating white blood cells, in particular [[Neutrophils|neutrophils]], begin adherence to the altered endothelial surfaces.

# '''Emigration of leukocytes'''

# '''Emigration of leukocytes'''

#* [[Leukocytes|Leukocytes]] migrate through the altered endothelium to reach the injured area.

#* [[Leukocytes|Leukocytes]] migrate, by an active process, through the altered endothelium to reach the injured area. This process is called '''diapedesis'''. The cells are stimulated to do this by chemoattractants in the vicinity of the injury, for example the [[Cytokines|cytokines]] TNF-.

#* This is an active process - [http://www.cellsalive.com/chemotx.htm| chemotaxis].

#**  The cells are attracted to the endothelium by release of proteins, and  further into the tissues by factors released from cells in the damaged  area.

#** The emigrated leukocytes and components of the fluid exudate are also chemotactic.

#** The emigrated leukocytes and components of the fluid exudate are also chemotactic.

#** More cells and fluid are attracted to the area.  

#** More cells and fluid are attracted to the area.