Changes

==Evolution of a Thrombus==

==Evolution of a Thrombus==

 

If the animal survives the immediate effects of a thrombus, the thrombus may evolve in one of the following ways:

* If the animal survives the immediate effects of a thrombus, the thrombus may evolve in one of the following ways:

# The thrombus may gradually '''enlarge''' and eventually cause total '''obstruction''' of a vessel.

# The thrombus may gradually '''enlarge''' and eventually cause total '''obstruction''' of a vessel.

# The thrombus may be completely '''removed by fibrinolytic activity'''.

# The thrombus may be completely '''removed by fibrinolytic activity'''; fibrinolysis is a very active process and clots are usually removed within a few days of formation provided that blood flow is sufficient. An occlusive thrombus may prevent the necessary enzymes from reaching the clot but contraction of fresh clots under the influence of thrombasthenin (released by platelets) may provide a slit-like channel beside the thrombus that permits the blood flow to restart and  completely dissolve the clot.

#* Fibrinolysis is a very active process - clots are usually removed within a few days of formation.

# '''Organisation'''; a thrombus acts as a foreign body, causing an inflammatory response in the underlying blood vessel or heart wall. The external surface of the thrombus then quickly becomes covered by endothelium and is excluded from the clotting mechanism. [[Neutrophils|Neutrophils]] invade the mass and may reduce the centre. Occasionally, subsequent invasion by bacteria may lead to to purulent inflammation. Normally, fibroblasts and capillary buds follow the neutrophils into the thrombus and a fibrous vascularised connective tissue forms. Capillaries channels anastomose to produce vessels that traverse the thrombus and re-establish blood flow - this is known as canalisation of a thrombus. Fibrous tissue matures and contracts, eventually causing the thrombus to become incorporated into the vessel wall as a fibrous lump. A piece of the thrombus may '''break off and form an embolus'''.

#* Blood flow is crucial to the process of fibrinolysis.

#** An occlusive thrombus may prevent the necessary enzymes from reaching the clot.

#* To overcome occlusion, contraction of fresh clots under the influence of thrombasthenin (released by platelets) forms a slit-like channel beside the thrombus.

#** The blood that then flows past may completely dissolve the clot.

# '''Organisation'''

#* A thrombus acts as a foreign body, causing an inflammatory response in the underlying blood vessel or heart wall.

#* The external surface of the thrombus quickly becomes covered by endothelium.

#** Is excluded from the clotting mechanism.

#* [[Neutrophils|Neutrophils]] invade the mass and may digest the centre.  

#** Occasionally, subsequent invasion by bacteria may lead to to purulent inflammation.  

#** Normally, fibroblasts and capillary buds follow the neutrophils into the thrombus and a fibrous vascularised connective tissue forms.  

#*** Capillaries channels anastomose to produce vessels that traverse the thrombus and re-establish blood flow.

#**** This is known as canalisation of a thrombus.

#***  Fibrous tissue matures and contracts, eventually causing the thrombus to become incorporated into the vessel wall as a fibrous lump.

# A piece of the thrombus may '''break off and form an embolus'''.

[[Category:Arterial_Pathology]][[Category:Cardiovascular_System_-_Vascular_Pathology]][[Category:To_Do_-_Cardiovascular]]

[[Category:Arterial_Pathology]][[Category:Cardiovascular_System_-_Vascular_Pathology]][[Category:To_Do_-_Cardiovascular]]

[[Category:Venous_Pathology]]

[[Category:Venous_Pathology]]