Pathology 4

Question 1

Name the disorders of haemostasis

Answer 1

• Haemorrhage

- Thrombosis

Question 2

What factors may be affected leading to haemorrhage?

Answer 2

• Endothelium/blood vessel
• Platelets
• Coagulation factors

Question 3

How might the endothelium/blood vessels be altered in order to lead to haemorrhage?

Answer 3

• Trauma
• Erosion by inflammation/neoplasia
• Endotoxaemia
• Toxins
• Inherited conditions (e.g. Ehlers-Danlos syndrome)
• Acquired conditions (vit C deficiency)
• Vascular fragility

Question 4

How might platelets be altered leading to haemorrhage?

Answer 4

• Decreased paltelet number (thrombocytopaenia)

- Abnormal platelet function (thrombocytopathy)

Question 5

How might coagulation factors be altered leading to haemorrhage?

Answer 5

• Inherited deficiencies (e.g. haemophilia A/B, Von Willebrand’s disease)
• Acquired defects (e.g. severe liver disease, warfarin intoxication)

Question 6

What is petechia?

Answer 6

Pinpoint (1-2mm) haemorrhage

Question 7

What is ecchymosis?

Answer 7

Haemorrhage up to 2-3cm

Question 8

What is haematoma?

Answer 8

Haemorrhage in focal, confined space i.e. bruise

Question 9

What is haemoabdomen?

Answer 9

Blood in the abdomen

Question 10

What is haemoperitoneum?

Answer 10

Blood in the periotoneal cavity

Question 11

What is haemothorax?

Answer 11

Blood in the thoracic cavity

Question 12

What is haemopericardium?

Answer 12

Blood in the pericardial sac

Question 13

What determines the significance of a haemorrhage?

Answer 13

The amount, rate and location of blood loss

Question 14

What is thrombosis?

Answer 14

Formation of inappropriate clot of fibrin and/or platelets along with other blood elements

Question 15

What is a mural thrombus?

Answer 15

A thrombus that forms on the wall of blood or lymphatic vessel or the heart

Question 16

What is a thromboembolus?

Answer 16

A thrombus free in the lumen of a vessel

Question 17

What may lead to thrombosis?

Answer 17

• Endothelial injury
• Alterations in blood flow
• Hypercoagulability

Question 18

Give examples of endothelial injury that may lead to thrombosis

Answer 18

• Infectious agents
• Immune-medaited
• Toxins
• disseminated intravascular coagulation (DIC)
• Faulty intravenous injections

Question 19

Give examples of alterations in blood flow that may lead to thrombosis

Answer 19

• Local stasis/decreased blood flow
• Cardiac disease
• Aneurysm
• Hypovolaemia

Question 20

Give examples of hypercoagulabity conditions that may lead to thrombosis

Answer 20

• Inflammation
• Increased platelet activity
• Increased clotting factor activation
• Antithrombin III deficiency

Question 21

What is Virchow’s triad?

Answer 21

The factors (endothelial injury, hypercoagulability and abnormal blood flow) that may lead to thrombosis

Question 22

What determines the significance of a thrombus?

Answer 22

• Location
• Ability to disrupt perfusion in a dependent tissue (depends on size, rate of formation, and method or resolution or repair)

Question 23

What is a thromboembolus?

Answer 23

Portion or whole thrombus can break loose and enter circulation as an embolus

Question 24

Where are venous thromboemboli often found?

Answer 24

Typically lodge in pulmonary circulation

Question 25

Where are arterial thromboemboli often found?

Answer 25

Typically near sites of vascular bifurcation

Question 26

What are the consequences of pulmonary venous thromboemboli?

Answer 26

- Lead to respiratory problems | - Eventually lead to heart disease

Question 27

What are the potential alterations in blood flow called?

Answer 27

- Hyperaemia (increased blood flow) - Congestion (decreased blood flow) - Decreased tissue perfusion

Question 28

What are the characteristics of hyperaemia?

Answer 28

- Active engorgement of vascular beds - Inflow increased (via arteriolar dilation) - Outflow may be normal or decreased

Question 29

What may cause hyperaemia?

Answer 29

- Physiologic: heat (skin), postprandially (GI) | - Pathologic: inflammation

Question 30

What are the characteristics of congestion?

Answer 30

- Passive engorgement of vascular beds - Outflow decreased - Inflow normal or increased

Question 31

What may cause congestion?

Answer 31

- Acute: heart failure, euthanasia, anaesthesia | - Chronic: obstruction of venous outflow, heart failure, pulmonary disease

Question 32

What may lead to decreased tissue perfusion?

Answer 32

- Obstruction of a blood vessel - Local vascular congestion - Decreased cardiac output

Question 33

What is an infarct?

Answer 33

An area of ischaemic necrosis caused by the occlusion of either arterial supply or venous drainage

Question 34

What does infarction commonly occur secondary to?

Answer 34

Thrombosis/thromboembolism

Question 35

What factors influence the development of an infarct?

Answer 35

- Nature of vascular supply (e.g. kidney and spleen have end-arterial supply) - Rate at which occlusion develops - Vulnerability to hypoxia - Oxygen content of the blood (i.e. venous or arterial)

Question 36

What is the effect of slow infarct development?

Answer 36

Provides time to develop alternate perfusion pathways

Question 37

What are the characteristics of infarct following arterial obstruction?

Answer 37

- Loss of blood flow to downstream tissue | - Abrupt coagulative necrosis downstream of obstruction

Question 38

What are the characteristics of infarct following venous obstruction?

Answer 38

- Stagnation of blood flow, reduction or loss of venous return - Progressive ischaemia and ultimately coagulative necrosis of tissue upstream of obstruction site

Question 39

What is DIC?

Answer 39

Disseminated Intravascular Coagulation

Question 40

What is DIC?

Answer 40

Serious manifestation of abnormal coagulation that leads to severe dyshaemostasis, caused by generation of excess thrombin

Question 41

What are the potential causes of DIC?

Answer 41

- Diffuse vascular damage - Systemic infections - Any other stimuli that activate release of inflammatory mediators - Massive anaphylactic events

Question 42

Describe the mechanism of DIC

Answer 42

- Excess thrombin leads to platelet aggregation and fibrin formation - Get widespread microvascular clots - Consumption of coagulation factors - Widespread haemorrhages occur as clots are using up coagulation factors

Question 43

What is shock?

Answer 43

Cardiovascular collapse

Question 44

Give the sequence of events in shock

Answer 44

- Hypotension - Decreased tissue perfusion - Cellular hypoxia - Shift to anaerobic metabolism - Cellular degeneration - Cell death

Question 45

What are the different types of shock?

Answer 45

- Cardiogenic - Hypovolaemia - Blood maldistribution

Question 46

What is cardiogenic shock?

Answer 46

Failure of the heart to adequately pump blood

Question 47

What is hypovolaemic shock?

Answer 47

Decreased circulating blood volume due to blood or fluid loss

Question 48

What are the 3 types of blood maldistribution shock?

Answer 48

- Anaphylactic - Neurogenic - Septic

Question 49

What causes anaphylactic shock?

Answer 49

Generalised type 1 hypersensitivity

Question 50

What causes neurogenic shock?

Answer 50

Trauma to the nervous system, may be elctrocution, fear, emotional stress

Question 51

What causes septic shock?

Answer 51

- Peripheral vasodilation caused by components of bacteria (endotoxin) or fungi - Induce release of excessive amounts of vascular and inflammatory mediators

Question 52

What factors need to be included in the gross description of an abnormality in post mortem?

Answer 52

- Location - Number/extent - Demarcation (well/poor) - Distribution (focal, multifocal, locally extensive, diffuse etc) - Colour - Size (metric units) - Shape - Consistency and texture - Extent (% of organ affected) - Any other information e.g. odour, sound

Question 53

What factors relating to the carcase need to be described in post mortem?

Answer 53

- Main features - Weight - Age - Breed - Species - Sex - Body condition - Any identifying feature e.g. tattoos, tags - Abnormaities - Degree of post-mortem decomposition

Question 54

In what way should a morphological diagnosis be written?

Answer 54

Organ: severity, duration, distribution, descriptors, diagnosis