Blood clotting Flashcards
what is haemostasis?
process that helps your body stop bleeding
What are the key cellular components of blood?
Erythrocytes (red blood cells)
Leukocytes (white blood cells)
Platelets
These are suspended in plasma (watery ECF)
what is the normal colour of blood plasma?
It has a pale colour. its colour indicates healthy blood
There are a range of proteins in blood plasma. How can they be separated?
electrophoresis
What proteins are included in the blood plasma?
Albumin
Fibrinogen (clotting protein)
Immunoglobulins
What are the properties of Erythrocytes (RBC)?
most abundant cell in blood (haematocrit)
Non-nucleated biconcave discs maximising SA:Vol
Mainly composed of Haemoglobin
Shape maintained by cytoskeleton anchored to plasma membrane
what is haematocrit?
*Think of blood samplec
Height of RBC / Total height
What are the mechanisms of Haemostasis?
Vasoconstriction (contraction)
Increase tissue pressure
Platelet plug (primary haemostasis) - these are made instantly and temporary
Clot formation (secondary haemostasis)
What are the properties of Platelets?
Nucleus free fragments (2-3 microns diameter)
Contain alpha granules (contain VWF, fibrinogen, clotting factor, platelet derived growth factor)
External coat rich in platelet receptors
cytoskeleton contains actin and myosin –> dispersed at rest / dynamic shape change in activation / clot retention
why are alpha granules important in platelets?
Alpha granules release von Willebrand factor (VWF), a protein that helps platelets adhere to the injured blood vessel wall.
They release fibrinogen, a protein that binds to receptors on platelets, facilitating their aggregation and the formation of a platelet plug.
platelet derived growth factor- important for wound healing
What are the three major functions of erythrocytes?
O₂ carriage from lungs to systemic system
CO₂ carriage from tissues to lungs
Buffering of acids/bases
What are the three stages of platelet plug formation?
The three stages are:
Adhesion
Activation
Aggregation
Describe the process of platelet adhesion
*Platelet plug formation is a rapid temporary seal to
prevent further blood loss
Damage to endothelium exposes subendothelial collagen – most thrombogenic (blood clotting)
Plasma VWF binds to exposed collagen and platelet receptors
Binding of platelet receptors cascade of IC events
Describe the process of Platelet Activation
Secretion platelet derived growth factor (PDGF) –> cell proliferation and wound healing
Thromboxane –> vasoconstriction + inflammation
Cytoskeletal changes *
Expression of fibrinogen receptors *
Describe the process of Platelet Aggregation
Platelet fibrinogen receptors bind to plasma fibrinogen *
forms molecular bridges between platelets –> aggregation
plugs breach the endothelium
eventually actin and myosin contract –> more compact platelet plug
What is the composition of a blood clot?
Erythrocytes
Leukocytes
Serum
Mesh of fibrin (and platelets)
What are the 2 pathways of clotting?
Intrinsic
Extrinsic
Describe the intrinsic and extrinsic pathways of clotting
Intrinsic- slower, activated by surface damage
Activated platelet initiates a cascade of protease reactions ending in activated factor 10a
Extrinsic- activated by trauma or inflammation
Injury to endothelium results in activated factor 10a
The intrinsic and extrinsic pathway form a common pathway. What is the common pathway?
Factors 10a from both pathways enters common pathway to generate thrombin (enzyme) that forms the final part which is fibrin –> fibrin forms the mesh like clot
What are the factors that promote Anti-thrombotic state? (so not making a clot)
Normal endothelial cells
Paracrine factors - e.g. prostacyclin promotes vasodilation, nitric oxide WHICH inhibits platelet adhesion and aggregation
Many anti-coagulant factors (including thrombomodulin - complexes with thrombin)v
What would promotion of pro-thrombotic state cause?
-Promotion of pro-thrombotic state VIA
Event of vascular damage
-Leads to hypoxia (lack of oxygen) –> leading to expression of procoagulants
Whats the difference between normal and abnormal blood flow, and what leads to abnormal blood flow?
Normal –> parabolic profile - fast flow in the middle and velocity decreases as you get closer to the sides
Abnormal –> turbulent - may blood flow leads to endothelial injury
what would cause turbulent flow in blood flow?
Turbulent flow caused by:
Local stenosis (narrowing of blood vessel)
Large radius (e.g. aorta) - not something to worry about tho
High velocity (e.g. high cardiac output) - not something to worry about tho
what is thrombus?
A blood clot that forms within blood vessels or chamber of heart
