Pathology 4 Flashcards
Name the disorders of haemostasis
- Haemorrhage
- Thrombosis
What factors may be affected leading to haemorrhage?
- Endothelium/blood vessel
- Platelets
- Coagulation factors
How might the endothelium/blood vessels be altered in order to lead to haemorrhage?
- Trauma
- Erosion by inflammation/neoplasia
- Endotoxaemia
- Toxins
- Inherited conditions (e.g. Ehlers-Danlos syndrome)
- Acquired conditions (vit C deficiency)
- Vascular fragility
How might platelets be altered leading to haemorrhage?
- Decreased paltelet number (thrombocytopaenia)
- Abnormal platelet function (thrombocytopathy)
How might coagulation factors be altered leading to haemorrhage?
- Inherited deficiencies (e.g. haemophilia A/B, Von Willebrand’s disease)
- Acquired defects (e.g. severe liver disease, warfarin intoxication)
What is petechia?
Pinpoint (1-2mm) haemorrhage
What is ecchymosis?
Haemorrhage up to 2-3cm
What is haematoma?
Haemorrhage in focal, confined space i.e. bruise
What is haemoabdomen?
Blood in the abdomen
What is haemoperitoneum?
Blood in the periotoneal cavity
What is haemothorax?
Blood in the thoracic cavity
What is haemopericardium?
Blood in the pericardial sac
What determines the significance of a haemorrhage?
The amount, rate and location of blood loss
What is thrombosis?
Formation of inappropriate clot of fibrin and/or platelets along with other blood elements
What is a mural thrombus?
A thrombus that forms on the wall of blood or lymphatic vessel or the heart
What is a thromboembolus?
A thrombus free in the lumen of a vessel
What may lead to thrombosis?
- Endothelial injury
- Alterations in blood flow
- Hypercoagulability
Give examples of endothelial injury that may lead to thrombosis
- Infectious agents
- Immune-medaited
- Toxins
- disseminated intravascular coagulation (DIC)
- Faulty intravenous injections
Give examples of alterations in blood flow that may lead to thrombosis
- Local stasis/decreased blood flow
- Cardiac disease
- Aneurysm
- Hypovolaemia
Give examples of hypercoagulabity conditions that may lead to thrombosis
- Inflammation
- Increased platelet activity
- Increased clotting factor activation
- Antithrombin III deficiency
What is Virchow’s triad?
The factors (endothelial injury, hypercoagulability and abnormal blood flow) that may lead to thrombosis
What determines the significance of a thrombus?
- Location
- Ability to disrupt perfusion in a dependent tissue (depends on size, rate of formation, and method or resolution or repair)
What is a thromboembolus?
Portion or whole thrombus can break loose and enter circulation as an embolus
Where are venous thromboemboli often found?
Typically lodge in pulmonary circulation
Where are arterial thromboemboli often found?
Typically near sites of vascular bifurcation
What are the consequences of pulmonary venous thromboemboli?
- Lead to respiratory problems
- Eventually lead to heart disease
What are the potential alterations in blood flow called?
- Hyperaemia (increased blood flow)
- Congestion (decreased blood flow)
- Decreased tissue perfusion
What are the characteristics of hyperaemia?
- Active engorgement of vascular beds
- Inflow increased (via arteriolar dilation)
- Outflow may be normal or decreased
What may cause hyperaemia?
- Physiologic: heat (skin), postprandially (GI)
- Pathologic: inflammation
What are the characteristics of congestion?
- Passive engorgement of vascular beds
- Outflow decreased
- Inflow normal or increased
What may cause congestion?
- Acute: heart failure, euthanasia, anaesthesia
- Chronic: obstruction of venous outflow, heart failure, pulmonary disease
What may lead to decreased tissue perfusion?
- Obstruction of a blood vessel
- Local vascular congestion
- Decreased cardiac output
What is an infarct?
An area of ischaemic necrosis caused by the occlusion of either arterial supply or venous drainage
What does infarction commonly occur secondary to?
Thrombosis/thromboembolism
What factors influence the development of an infarct?
- 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)
What is the effect of slow infarct development?
Provides time to develop alternate perfusion pathways
What are the characteristics of infarct following arterial obstruction?
- Loss of blood flow to downstream tissue
- Abrupt coagulative necrosis downstream of obstruction
What are the characteristics of infarct following venous obstruction?
- Stagnation of blood flow, reduction or loss of venous return
- Progressive ischaemia and ultimately coagulative necrosis of tissue upstream of obstruction site
What is DIC?
Disseminated Intravascular Coagulation
What is DIC?
Serious manifestation of abnormal coagulation that leads to severe dyshaemostasis, caused by generation of excess thrombin
What are the potential causes of DIC?
- Diffuse vascular damage
- Systemic infections
- Any other stimuli that activate release of inflammatory mediators
- Massive anaphylactic events
Describe the mechanism of DIC
- 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
What is shock?
Cardiovascular collapse
Give the sequence of events in shock
- Hypotension
- Decreased tissue perfusion
- Cellular hypoxia
- Shift to anaerobic metabolism
- Cellular degeneration
- Cell death
What are the different types of shock?
- Cardiogenic
- Hypovolaemia
- Blood maldistribution
What is cardiogenic shock?
Failure of the heart to adequately pump blood
What is hypovolaemic shock?
Decreased circulating blood volume due to blood or fluid loss
What are the 3 types of blood maldistribution shock?
- Anaphylactic
- Neurogenic
- Septic
What causes anaphylactic shock?
Generalised type 1 hypersensitivity
What causes neurogenic shock?
Trauma to the nervous system, may be elctrocution, fear, emotional stress
What causes septic shock?
- Peripheral vasodilation caused by components of bacteria (endotoxin) or fungi
- Induce release of excessive amounts of vascular and inflammatory mediators
What factors need to be included in the gross description of an abnormality in post mortem?
- 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
What factors relating to the carcase need to be described in post mortem?
- Main features
- Weight
- Age
- Breed
- Species
- Sex
- Body condition
- Any identifying feature e.g. tattoos, tags
- Abnormaities
- Degree of post-mortem decomposition
In what way should a morphological diagnosis be written?
Organ: severity, duration, distribution, descriptors, diagnosis
