[A] 1.21 Thrombosis

Question 1

Define: Thrombosis

Answer 1

• A sold mass formed from blood constituents in a vessel or hear lumen during life
• Inappropriate formation of thrombus

Question 2

Factors predisposing to thrombosis

Answer 2

Alterations in:

• Vascular endothelium
• Blood flow
• Blood constituents

Question 3

Alterations in the vascular endothelium leading to thrombosis

Answer 3

• Vascular damage, endothelial injury
  
  • Viral, bacterial, fungal, parasitic
• Immune-mediated vasculitis
• Exposure of collagen, release of inflammatory mediators

Question 4

Alterations in blood flow leading to thrombosis

Answer 4

• Prestasis, stasis → Reduced flow
• Turbulence (caused by an aneurysm)
• Circulatory disturbances → Hypovolaemia, shock
• Cardiopathy → Cardiomyopathy

Question 5

Alterations in blood constituents leading to thrombosis

Answer 5

• ↑ Number of platelets
• ↑ Adhesivity of platelets
• Changes in blood constituent proportion
• ↑ Conc. of aggregation promoting substances
• ↓ Conc. of anti thromboplastic substances

Question 6

The appearance of thrombi depends on

Answer 6

• Underlying cause
• Location
• Composition

Question 7

The significance of thrombi depends on their

Answer 7

• Location
• Ability to disrupt blood flow, perfusion
• Rate of formation/ size

Question 8

List the forms of thrombus

Answer 8

• White/pale thrombus
• Red thrombus
• Mixed thrombus
• Hyaline thrombus (Fibrin thrombus in small vessels)

Question 9

White thrombus

Answer 9

“Conglutination thrombus”

• Vascular damage
• Attachment of the thrombocytes
• Fibrin accumulation
  
  • Grey-white mass attached to the endothelium
  • Fibrin only

Question 10

Red thrombus

Answer 10

“Coagulation thrombus”

• Composed of fibrin, thrombocytes & RBCs
• Seen in stasis
• Coupled with white thrombus

Question 11

Red thrombus is usually accompanied by…

Answer 11

White thrombus

• In the case of obturation
• Before or after → Stasis of the blood

Question 12

Red thrombus stasis for any reason can lead to…

Answer 12

• Heart failure
• Right side failure
  
  • Tr. pulmonalis, lung
• Hypoalbuminaemia
  
  • Cachexia, liver/kidney failure

Question 13

Mechanism of thrombosis

Answer 13

• Stasis
  
  • Plasma
  • Higher viscosity
  • Higher resistance the lumen
  • Slowing down of blood flow

Question 14

Hyalin thrombi

Answer 14

• Hypercoagulobility of the blood
  
  • ↑ Thrombocytes, fibrinogen & globulins
  • Substances causing thrombocyte aggregation
  • Shock → Endotoxins
• Plasma or fibrin thrombi
• In the small blood vessels
  
  • Arterioles, venules
  • Terminal circulatory bed

Question 15

Summarise DIC

Answer 15

Disseminated intravascular coagulopathy

• Pathologic activation of the clotting cascade
• Exposure of blood to tissues factor

Can be caused by septicaemic, toxaemia, shock, acidosis, necrosis

Question 16

Forms of the thrombi

Answer 16

Mural thrombus (parietal with tail)

• White thrombus: Mural → occlusive

Occlusive thrombus

• Red thrombus

Question 17

Outcomes of thrombosis

Answer 17

• Healing - After vessel injury
• Organ failure, sudden death
• Local/systemic circulatory disturbance
  
  • Stenosis
• Heart
  
  • Stenosis
  • Cardiac valvular insufficiency
• Thromboembolism

Question 18

Fate of the thrombus (generally)

Answer 18

• Complete elimination by fibrinolysis
  
  • 1-2 days
• Colliquation
  
  • By proteolytic enzymes of granulocytes
  • By pyogenic bacteria
• Endothelisation
  
  • Afer 1 week

Question 19

Fate of a thrombus after 1 week

Answer 19

• Organisation, calcification
• Recanalisation (channel formation)
• Embolus formation

Question 20

Thrombosis in species

Answer 20

• Horse: A. mesenterialis cran., abdominal aorta
• Cattle: Wall of the uterus
• Cat: Abdominal aorta
• Swine, cattle dog: Endocarditis

Question 21

Mixed thrombi

Answer 21

• Changes in the circumstances
• White-red-white-red

Question 22

Thrombosis of the lymph vessels

Answer 22

Plasma thrombi