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Flashcards in Thrombosis Deck (23):

Describe the typical structure of an artery or arteriole

Endothelial cells lining the lumen

Surrounded by basal lamina (made by endothelial cells)

Smooth muscle cells surround basal lamina

Interstitial collagen fibres (collagen in connective tissue between structures) surrounds this


What is the difference between serum and plasma?

Plasma contains clotting factors

Serum is plasma without clotting factors


Where are clotting factors mainly produced?

Endothelial cells


Describe the clotting cascade (amplification sequence) when there is damage to a tissue

1) Damage exposes interstitial collagen fibres and tissue factor

2) TF reacts with various clotting factors, finally producing Xa-Va

3) Promthrombin is converted to thrombin

3) Thrombin causes soluble fibrinogen to to polymerise to form insoluble fibrin

4) Fibrin cross links leading to coagulation


How is the clotting cascade (amplification sequence) initiated?

1) Trauma ∴ blood leaks out of blood vessel

2) Clotting factors in contact with interstitial collagen fibres ∴ activated

3) Tissue factor is released from smooth muscle cells

4) TF binds to clotting factor ∴ initiates clotting cascade


Describe the structure of most clotting factors and how most are activated

Many CF are serine proteases

They have serine Amino Acid section and enzyme section

- CF cleaves next CF in cascade
- Producing active CF and redundant fragment


How are platelets produced?

Produced in bone marrow

From cell called a megakaryocyte

(large cell with many nuclei)

Platelets synthesised in the cell and bud off as fragments from cytoplasmic extensions


Describe how platelets work as coagulants

1) Trauma ∴ exposure of platelets to interstitial collagen

2) Platelets clump together and try to form a bridge to close gap in the blood vessel


What is coagulation?

Solidification of blood

Two types:
1) Thrombus formation
2) Clot formation


What is the difference in the composition of a thrombus and a clot?

Thrombus - Mesh network of fibrin strands + platelets

Clot - Mesh of fibrin strands + RBCs


What are the conditions for the formation of a clot and a thrombus? How are the different?

Thrombus occurs when there is flowing blood

Clots occur when the blood flows out and become stationary


What feature of platelets allow thrombus formation in flowing blood?

They have molecules on their surface that allow adherence to interstitial collagen


What is the function of coagulants?

Haemostasis - stopping bleeding


What ways does the body try to minimise/stop bleeding?

- Clot/thrombus formation

- Vessel vasoconstriction of damaged vessel


Describe how clot and thrombus formation are used together to achieve homeostasis

Clots form in the space around the vessel to fill the void of the wounded tissue

Thrombus forms to seal the gaps in the blood vessel


After a wound is successfully plugged, what will happen?

Angiogenesis - capillaries grow into clot

It becomes granulation tissue

Blood supply provides oxygen/nutrients etc and keeps GT alive


What is ischaemia?

Lack of blood flow to tissues

Can happen if thrombus blocks blood flow

Will lead to hypoxia (lack of oxygen)


Aside from ischaemia & hypoxia, what negative effect cam thrombus formation have?

Blocks blood flow ∴ stagnant blood behind it ∴ clotting

Lead to a mixture of clot and thrombus


Under normal circumstances, once a blood vessel is repaired, then the clot and thrombus are removed.

How is excess thrombus and clot removed?

Fibrinolytic system present in blood

Fibrinolytic = breaks down fibrin

This stops thrombi from propagating


How does the fibrinolytic system work?

Consists of a plasma protein called plasminogen

This is converted to plasmin

Plasmin breaks down fibrin strands


What does Virchow's triad describe?

Factors that cause abnormal clotting/thrombosis which can lead to many diseases


What is Virchow's triad?

Abnormalities of vessel wall

Abnormalities of components of the blood

Abnormalities of vessel flow


Why is Virchow's triad useful?

It defines the 3 abnormalities that lead to thrombosis/clotting in disease