Differences between thrombus and blood clot
Thrombus
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Blood clot
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Formation
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Blood vessels
Platelets
Blood clotting system
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Blood clotting system
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Composition
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Platelets
Fibrin
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Only fibrin
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Prognosis
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Life threatening
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Life saving
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Causes for
- Injury to endothelium
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Trauma : lacerations, contusion, rupture, i/r injection
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Toxins : Streptococci, erysipelothrix (vegetations)
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Degenerations : Atherosclerosis (damage to intima)
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Viruses : Hog cholera virus
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Parasites : Strongylus vulgaris in anterior mesenteric artery in horses
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Tumours : Invading tumours
Mechanism of thrombus formation
- Active
- Antithrombotic factors and prothrombotic factors are seen on surface of endothelium
- Passive
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Endothelium is thromboresistant wheras subendothelial connective tissue is highly thrombogenic.
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Subendothelial onnective tissue consists of collagen, elastic, fibrinonectin, laminin glycosoaminoglycans and thrombosporin.
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Damage to endothelium exposes the subendothelial connective tissue and activates intrinsic blood clotting pathway and platelet adhesion.
Antithrombotic factors (present on endothelial cells) - Inhibit thrombosis
Thrombotic factors
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Tissue factor (Thromboplastin)
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von Willebrand factor (vWF)
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Platelet Activating Factor (PAF)
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Inhibitor of Plasminogen Activator
Normal homeostasis: There will be a balance between antithrombotic and prothrombotic factors in normal endothelium.
Thrombus formation
Alterations in constituents of blood
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Increase in number of platelets
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Increase in adhesiveness of platelets
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Decrease in heparin (anticoagulant) in diseases
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Increased plasma fibrinogen and prothrombin
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Increased viscosity of blood
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Sludging of blood
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Increased fragility of RBCs
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Increased cortisone therapy – Rheumatoid arthritis - Increase blood lipids - Increase platelet aggregation - Coronary thrombosis
Alterations in normal blood flow
Types of thrombus
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Arterial thrombus
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Venous thrombus
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Cardiac thrombus
Causes for slowing of blood
Comon sites for thrombosis
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Animals
- Scrotal plexus - horses
- Vascular sinuses – horse and cows (Nasal passage)
- Large veins of Broad ligament of uterus – cow
- Anterior mesenteric artery - horses
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Humans
- Leg veins – Congestive heart failure, bed ridden patients
I. Based on location within blood vascular system
1.Cardiac thrombi
- Mural thrombus: Seen on the wall of left auricle
- Bovines - black quarter
- Caused by Clostridium chauvoei
- Valvular thrombus
- Pigs – Streptococcus pyogenes, Erysipelothrix rhusiopathiae
- Cattle– Cornybacterium pyogenes
- Horses– Streptococcus equi
- Ball thrombus: Seen in auricle - Unattached. If it is large,it causes valvular obstruction
2. Arterial thrombi
- Located within arteries
- Common in domestic animals
- Horses : Strongylus vulgaris larvae in anterior mesenteric artery
- Dogs : Spirocerca lupi in aorta
- Cattle: Onchocerca armillata in aorta
3. Venous thrombi
- Phlebothrombosis
- Common in bed ridden patients
- Rare in animals
- Seen in recumbent calves
Leg veins collapse and press against hard surface. Endothelium gets damaged and thromboplastin is released resulting in thrombus formation. In general passive hyperaemia, veins will be distended and leads to slowing of blood which favours thrombus formation.
Locations
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Human - Femoral, popliteal, iliac veins
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Animals
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Nasal vascular sinuses – Cow, horses
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Veins of broad ligament – Cow
4. Capillary thrombi
5. Lymphatic thrombi
II. Classification based on location within heart or bood vessels
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Mural thrombi - Attached to wall of heart / blood vessel
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Valuvlar thrombi - Valves
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Lateral thrombi - Attached to one side of blood vessel
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Occlusive thrombi - Attached to entire circumference of vessel
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Saddle thrombi -Site of bifurcation of blood vessel
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Canalised thrombi - New blood channel is formed through clot
III. Classification based on infectious agent
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Septic thrombi - Bacteria
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Aseptic thrombi - Without bacteria / parasites
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Parasitic thrombi - Strongylus vulgaris (Horses) and Dirofilaria immitis (Dogs)
IV. Classification based on colour of thrombi
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Pale / White Thrombi - composed of platelets and are seen in heart / aorta
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Red Thrombi – composed of platelets / fibrin, RBCs and WBCs and are seen in veins ( Commonly seen)
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Mixed Thrombi –Mixture of White and red thrombi (White - Formed during fast flow of blood; Red - Formed during sluggish flow)
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Laminated thrombi
Fate of thrombus
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Propagation : Enlargement - obstruction of vessel
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Contraction : Shrinkage of thrombus may occur due to contraction of fibrin
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Embolus : Carried to other sites; and cause dangerous infarction
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Abscessation : Pyogenic bacteria in thrombus may gives rise to bacterial emboli
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Resolution : Fibrinolysis
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Organization & Canalisation
Significance and results
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Negligible effects - Jugular vein; carotid arteries
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Beneficial effects - Control of haemorrhages
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Harmful effects - Vessel without collateral circulation
Character
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Thrombus
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Postmortem clot
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Size
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Fills vessels
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Small
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Consistency
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Dry & friable
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Smooth / glistening
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Color
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White, red, mixed
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Red / yellow
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Attachment
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Yes
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No
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Endothelium
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Damaged
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Undamaged
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Composition
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Platelets
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Fibrin
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Rapidity of blood flow
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Formed in flowing stream
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Stagnant stream
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Animal
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Living
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Dead
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Organization
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Yes
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No
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Structure
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Laminated (Line of Zahn)
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Homogenous
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