This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
A major source of Von Willebrand factor (vWF) - 
Select and explain. 
A. Erythrocytes, B. Neutrophils, C. Endothelial cells, D. Monocytes
C: Endothelial cells
Answer: C: Endothelial cells 
Explanation: Circulating factor VIII has two components.
(a) Factor VIII c  (Procoagulant protein)

This is the smaller component
It is synthesized in the liver (main source) and kidney.
It is an intrinsic pathway component required for activation of factor X.

(b) Von willebrand factor (vWF)

This is the larger component
It is produced by endothelial cells (main source) and megakaryocytes.
It has two major functions.



Helps in platelet adhesion by interacting platelet membrane glycoprotein Ib-IX.


Stabilizes factor VIIIc.