Question

Discuss the processes of hemostasis and fibrinolysis, but do not list all the coagulation factors (e.g., factors VII, VIII, etc) – I only look for essential ones that initiate the three different coagulation pathways and the final activation mechanism of fibrin formation. Which ion and vitamin play essential roles in hemostasis? Which hematopoietic cell is responsible for the production of platelets? Warfarin is an example of anticoagulants that are clinically used. What are other examples of anticoagulants you learned in the class? Which factor acts as a thrombolytic agent that helps dissolve thrombi or emboli in stroke or heart attack patients?

Answer 1

1)Homeostasis --->The process by which the body seals a ruptured blood vessel and prevents further loss of blood.
Platelets play an important role in homeostasis .

2)Fibrinolysis ---->It is the process in which enzymatic breakdown of fibrin in blood clot.Process by which Plasminogen is activated to form Plasmin and thus it help in lysis of thrombus .

Homeostais -It occur in three steps
1. INJURY --When there is injury to blood vessel blood and blood components ( RBc,Wbc ) leak out of blood vessels.

2.Vascular spasm --Immediately smooth muscle contraction occur and reducing the blood loss .

3.Platelet plug formation --Paltelets are exposed to subendothelial matrix and collagen tissues .Process is assisted by Von willebrand factor glycoprotein in plasma which helps in formation of platelet plug .

Coagulation pathways --
There are three ways by which it is activated
1.Intrinsic pathway --when there is injury to blood vessels .
2. Extrinsic pathway --when there is trauma to extravascular cells tissue injury occur .
3. Common pathway --Both intrinsic and extrinsic finally activate the common pathway and help in stabilisation of clot formation

Both intrinsic and extrinsic pathway cause activation of factor 10
Factor X -------------->>>Factor Xa
It requires calcium ions for its activation

Factor Xa activate Prothrombin to Thrombin with help of calcium ion

Thrombin finally convert fibrinogen to Fibrin and help in stabilisation of clot .

3)VITAMIN K and CALCIUM ions play essential role in homeostasis .
The liver requires the fat-soluble vitamin K to produce coagulation factors .Factor 2,7,9 and factor 10 are dependenton Vit K for their shnthesis .The calcium ion, considered factor 4 also play important role in homeostais.

4)MEGAKARYOCYTE is responsible for production of platelets .
Megakaryocytopoiesis is the process that leads to the production of platelets. This process involves the commited cells for production of platelets are formed from multipotent hematopoietic stem cells
Known as megakaryocyte (MK) progenitors, the proliferation and differentiation of MK progenitors is reponsible for platelet production under the influence of thrombopoeotin .Thrombopoeotin is glycopeotein produced by kidney and liver and hep in regualation of platelet production by acting on Megakaryocytes .

5)Three major groups of anticoagulants used are
Oral drugs --->
1. Vitamin K knhibitors -
-Warfarin
-Dicumarol
-Phenindione
2.Factor Xa inhibitor
-Rivaroxaban
-Apixaban
3.Direct thrombin inhibitors
Ximelagatran
Dabigatran

Parentral drugs
1. Indirect thrombin inhibitors
-- Unfractionated heaprin
---Low molecular weight heparin
a) Enoxaparin
b) Dalteparin
c)Tinzaparin
---Fondaparinux ,Idraparonux

2. Direct thrombin inhibitors
--Hirudin
--Lepirudin
--Argatroban
--Melagatran .