Bleeding And Impaired Hemostasis

Question 1

Hemostasis

Answer 1

2 stages -
Primary hemostasis - Endothelial cells start releasing proteins, platelets clump up at the site of injury resulting in platelet plug.
Secondary hemostasis - Fibrinoid attaches to platelet plug to strengthen it, coagulation factors get activated -> Fibrinogen turns into Fibrin -> coagulation cascade -> clot at injured site

Question 2

Primary hemostasis

Answer 2

Step 1 - vasoconstriction -> nerve reflex or Endothelin
Step 2 - platelet adhesion -> VWF binds to the injured site
Step 3 - Activation and Degradation -> granules release proteins such as - Fibrin, Thromboxane and SAC
Step 4 - platelet aggregation - clumping and platelet plug forms

Question 3

Secondary hemostasis

Answer 3

Coagulation cascade leads to fibrin from Fibrinogen. Coagulation cascade gets activated two ways - subendothelial collagen -> Intrinsic pathway , Tissue factor / Thromboplastin -> Extrinsic pathway. Formation of fibrin mesh has Ca2+ and phospholipid surface -> stable clot

Question 4

How do we make blood clots ?

Answer 4

After a blood vessel damages, the collagen outside blood vessel attracts platelets to clump and form platelet plug at the site. After platelet plug forms Fibrinogen turns into fibrin at damage site due to presence of Tissue factors (present at the endothelial cells), then Fibrin polymerizes to form a mesh forming clot.

Question 5

Coagulation cascade

Answer 5

Intrinsic pathway -> one factor catalyzes for transformation of other
Extrinsic pathway -> gets initiated by damage and shoots straight up
If these pathways fail Hemophilia occurs - uncontrolled bleeding
Hemophilia A - clotting factor 8 deficiency
Hemophilia B - clotting factor 9 deficiency
Hemophilia c - clotting factor 11 deficiency

Question 6

Anticoagulation and Thrombolysis

Answer 6

Heparin like molecules (found on endothelial cells) interacts with anti-thrombin 2 -> inhibits 10 factor and thrombin -> prevents fibrin formation
Another way - the complex of protein c, protein s, thrombin and thrombomodulin -> inhibits 5 and 8 factors -> anticoagulations plasmin (breaks down fibrin) -> comes from plasminogen -> healthy endothelial cells produce tissue plasminogen factor -> thrombolysis