Hemostasis - Blood Coagulation Flashcards
More than 50 important substances in the body affect coagulation. What are the two types and their respective purpose?
Pro coagulants : promote coagulation
Anti coagulants : inhibit coagulation
Which group of coagulation related substances normally predominate in the circulating blood?
Anti coagulants (so that the blood won’t coagulate in the vessels)
What are the 3 essential steps of clotting?
- In response to the damaged vessel ➡️ complex cascade of chemical reactions involving more than 12 blood coagulation factors take place ➡️
resulting in the formation of a complex of activated substances ➡️
Collectively known as Prothrombin activator - Prothrombin activator catalyzes
Prothrombin ➡️ Thrombin - Thrombin acts as enzyme to catalyze
Fibrinogen ➡️ Fibrin fibers
Other than prothrombin activator, what is needed for the conversion of prothrombin to thrombin?
Ca2+ ions
What is the rate limiting factor of blood coagulation?
Formation of prothrombin activator
What is the role played by platelets in the conversion of prothrombin to thrombin?
Much of the prothrombin first attaches to the prothrombin receptors on the platelets that are already bound to the damaged tissue.
What type of molecule is prothrombin? What is it’s molecular weight and concentration in normal plasma?
A plasma protein
α2-globulin

68,700
15 mg/dl
What is the site of prothrombin formation?
What is the nutrient required by it for the normal activation of prothrombin?
Liver
Vitamin K and few other clotting factors
What is the molecular weight of the plasma protein, fibrinogen? What is its concentration in the plasma?
~ 340,000
100 to 700 mg/dl
Where is fibrinogen formed?
What kind of diseases decreases the concentration of circulating fibrinogen?
Liver
Liver diseases
How does the weak proteolytic capabilities of the protein enzyme ‘thrombin’, affect fibrinogen?
It removes four low-molecular-weight peptides from each molecule of fibrinogen, forming one molecule of fibrin monomer.
Fibrin monomers polymerise with other fibrin monomer molecules to form fibrin fibres. Therefore many polymerise in seconds to form long fibrin fibres that constitute the reticulum of the blood clot.
Why is the resultant clot of the early stages of polymerisation, weak and broken apart with ease?
Because the fibrin monomer molecules are held together by weak noncovalent hydrogen bonding, and newly formed fibres are not cross linked with one another
Which substance involves in the process that greatly strengthens the fibrin reticulum?
Where is it present ?
Which structures release it?
Which substance activates it?
Fibrin stabilising factor
In normal plasma globulins in small amounts
It is released from platelets entrapped in the clot.
Thrombin
What does activated fibrin stabilising factor do?
Operates as an enzyme to form covalent bonds between more and more of the fibrin monomer molecules,
as well as multiple cross linkages between adjacent fibrin fibres
(thus adding tremendously to the three-dimensional strength of the fibrin meshwork)
Within 20 to 60 minutes after a clot is formed, it begins to contract and expresses most of the fluid. What is this fluid called?
Serum
