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New page: * An embolus is a detached intravascular mass that is carried by the blood to a site distant from its point of origin. ** May be solid or gaseous. * Emboli will lodge in a vessel too smal...
* An embolus is a detached intravascular mass that is carried by the blood to a site distant from its point of origin.
** May be solid or gaseous.
* Emboli will lodge in a vessel too small to permit further passage.
** Results in occlusion.
===Types of Embolism===
====Thromboembolism====
* These are pieces of thrombi that have broken away from their primary site.
* The most common cause of embolism.
====Air embolism====
* Caused by accidental injection of air from a badly filled hypodermic syringe.
* Small air bubbles may occlude the blood vessels of the brain and cause severe ischaemic necrosis.
====Fat embolism====
* Pieces of adipose tissue from the bone marrow cavity may enter the blood stream following fracture.
====Fibrocartilagenous embolus====
* Seen in the dog.
* Thought to arise from a damaged intervertebral disc.
* Cause occlusion of spinal blood vessels.
** Results in:
*** Spinal cord necrosis.
*** Severe sudden paralysis.
====Tumour emboli====
* Otherwise known as [[Neoplasia - Pathology#Dissemination of malignant neoplasia|metastasis]].
* Small groups of tumour cells may break off and be carried in vessels to reach another site
in the body.
* May use the lymphatic or blood vessels.
====Bacterial emboli====
* Some bacteria travel in colonies.
** Come to rest in small capillaries and incite an inflammatory response.
===The results of Embolism===
* The results of embolism depend on several factors.
*# The extent of the occlusion and the availability of an adequate collateral circulation.
*#* Some emboli may be irregularly shaped, allowing blood to flow around them.
*# Duration for which the embolus blocks a vessel.
*#* Some small thrombi may undergo lysis and quickly disappear.
*# Nature of the embolus.
*#* Bacterial emboli will incite an extensive inflammatory reaction.
*#* Tumour emboli will multiply and grow into tumour masses.
*# The site at which the embolus comes to rest.
*#* There are two main considerations here.
*#** The type of tissue supplied.
*#*** The brain and heart are quickly affected by anoxia.
*#** The type of blood supply to the tissue.
*#*** Occlusion of vessels to a tissue with an end arterial supply will cause '''ischaemic necrosis''' or '''infarction'''.
====[[Ischaemia and Infarction - Pathology#Ischaemia|Ischaemia]]====
* This is the local reduction of blood flow to an area.
** Usually refers to the arterial flow.
* Ischaemia may be partial.
** Results in hypoxia and atrophy of the tissue supplied.
====[[Ischaemia and Infarction - Pathology#Infarction|Infarction]]====
* Blockage of an end artery results in acute ischaemic coagulation necrosis, or infarction.
* Some end arteries and their branches are of particluar importance.
** The renal artery.
** The splenic artery.
** The coronary arteries.
** Some cerebral and spinal cord arteries.
** The anterior mesenteric artery.
* There are some areas that have a tendency for infarction.
** The kidneys of pigs and dogs.
** The spleen of the pig.
** The intestine of the horse.
** N.B Infarction of the heart and brain is rare in animals.
=====Kidney Infarcts=====
* Typically appear on the cortex.
* Appear as a sharply demarcated pale area surrounded by a red line of haemorrhage.
** A white line of [[[[Neutrophils|Neutrophils]] - WikiBlood|neutrophils]] forms inside the red line after a few days.
* The necrotic tissue undergoes liquefactive necrosis.
** The area is invaded by fibrous tissue.
*** Eventually the lesion ends up as a pale, depressed scar.
=====Splenic infarcts=====
* Appear red in colour due to haemorrhage into the necrotic area.
* This is an important diagnostic lesion in swine fever.
=====Intestinal Infarcts=====
* Small emboli break off followinf thrombosis and occlude intestinal vessels.
** Small intestinal infarcts develop.
*** Thought to cause bouts of colic.
* [[Strongylus vulgaris|''Strongylus vulgaris'']] may also cause intestinal infacts in the horse.
** Lodge at the root of the cranial mesenteric artery.
=====Lungs=====
* Emboli from the venous system may end up in the [[Lungs Circulatory - Pathology#Embolism, thrombosis and infarction|lung]].
* The lung has an extensive collateral cirulcation, and so little damage is caused.
[[Category:Arterial_Pathology]][[Category:Venous_Pathology]]
** May be solid or gaseous.
* Emboli will lodge in a vessel too small to permit further passage.
** Results in occlusion.
===Types of Embolism===
====Thromboembolism====
* These are pieces of thrombi that have broken away from their primary site.
* The most common cause of embolism.
====Air embolism====
* Caused by accidental injection of air from a badly filled hypodermic syringe.
* Small air bubbles may occlude the blood vessels of the brain and cause severe ischaemic necrosis.
====Fat embolism====
* Pieces of adipose tissue from the bone marrow cavity may enter the blood stream following fracture.
====Fibrocartilagenous embolus====
* Seen in the dog.
* Thought to arise from a damaged intervertebral disc.
* Cause occlusion of spinal blood vessels.
** Results in:
*** Spinal cord necrosis.
*** Severe sudden paralysis.
====Tumour emboli====
* Otherwise known as [[Neoplasia - Pathology#Dissemination of malignant neoplasia|metastasis]].
* Small groups of tumour cells may break off and be carried in vessels to reach another site
in the body.
* May use the lymphatic or blood vessels.
====Bacterial emboli====
* Some bacteria travel in colonies.
** Come to rest in small capillaries and incite an inflammatory response.
===The results of Embolism===
* The results of embolism depend on several factors.
*# The extent of the occlusion and the availability of an adequate collateral circulation.
*#* Some emboli may be irregularly shaped, allowing blood to flow around them.
*# Duration for which the embolus blocks a vessel.
*#* Some small thrombi may undergo lysis and quickly disappear.
*# Nature of the embolus.
*#* Bacterial emboli will incite an extensive inflammatory reaction.
*#* Tumour emboli will multiply and grow into tumour masses.
*# The site at which the embolus comes to rest.
*#* There are two main considerations here.
*#** The type of tissue supplied.
*#*** The brain and heart are quickly affected by anoxia.
*#** The type of blood supply to the tissue.
*#*** Occlusion of vessels to a tissue with an end arterial supply will cause '''ischaemic necrosis''' or '''infarction'''.
====[[Ischaemia and Infarction - Pathology#Ischaemia|Ischaemia]]====
* This is the local reduction of blood flow to an area.
** Usually refers to the arterial flow.
* Ischaemia may be partial.
** Results in hypoxia and atrophy of the tissue supplied.
====[[Ischaemia and Infarction - Pathology#Infarction|Infarction]]====
* Blockage of an end artery results in acute ischaemic coagulation necrosis, or infarction.
* Some end arteries and their branches are of particluar importance.
** The renal artery.
** The splenic artery.
** The coronary arteries.
** Some cerebral and spinal cord arteries.
** The anterior mesenteric artery.
* There are some areas that have a tendency for infarction.
** The kidneys of pigs and dogs.
** The spleen of the pig.
** The intestine of the horse.
** N.B Infarction of the heart and brain is rare in animals.
=====Kidney Infarcts=====
* Typically appear on the cortex.
* Appear as a sharply demarcated pale area surrounded by a red line of haemorrhage.
** A white line of [[[[Neutrophils|Neutrophils]] - WikiBlood|neutrophils]] forms inside the red line after a few days.
* The necrotic tissue undergoes liquefactive necrosis.
** The area is invaded by fibrous tissue.
*** Eventually the lesion ends up as a pale, depressed scar.
=====Splenic infarcts=====
* Appear red in colour due to haemorrhage into the necrotic area.
* This is an important diagnostic lesion in swine fever.
=====Intestinal Infarcts=====
* Small emboli break off followinf thrombosis and occlude intestinal vessels.
** Small intestinal infarcts develop.
*** Thought to cause bouts of colic.
* [[Strongylus vulgaris|''Strongylus vulgaris'']] may also cause intestinal infacts in the horse.
** Lodge at the root of the cranial mesenteric artery.
=====Lungs=====
* Emboli from the venous system may end up in the [[Lungs Circulatory - Pathology#Embolism, thrombosis and infarction|lung]].
* The lung has an extensive collateral cirulcation, and so little damage is caused.
[[Category:Arterial_Pathology]][[Category:Venous_Pathology]]