38 - Coagulation Series part 4 of 8

KYJ38 - Intrinsic Coagulation System. 4 of 7.


This is the 4th post in a series on Coagulation factors.
In the first three episodes we looked at the Tissue Factor Activation pathway- otherwise known as the Extrinsic pathway.

This edition of a KYJ looks at the initiation of the Intrinsic pathway, or more recently known as the Contact Activation.

Let's start with blood or more specifically Plasma.
Plasma is a cocktail of salts, glucose and proteins. Many of the proteins in plasma serve a role in coagulation, and to date, we have discussed Tissue factor 3, VonWillebrand Factor and the plasma Factors 7, 10, 2, and 1.

Well as you guessed, the numbers in between are all involved in the intrinsic pathway. Let's start with the contact (intrinsic) activation of the coagulation cascade.

If blood comes into contact with a negatively charged surface such as glass, foreign objects, bacteria, or Tissue factors released by damaged cells, it initiates the contact activation pathway.

It starts when a protein called "High-molecular-weight kininogen" (HMWK), (also known as the Williams-Fitzgerald-Flaujeac Factor ) that shares a role in both the coagulation system as well as the kinin-kallikrein system, is activated by a negatively charged contact.

Additionally, a factor called Hageman Factor (Factor XII) And another protein called Prekellikrein (PK)  also activates , and together the three proteins activate Factor 12 into Factor XIIa.

Hageman Factor  was named in 1955 after a Railway worker was found to be deficient in Factor XII. His blood simply wouldn't coagulate in a glass test tube.  Deficiency of factor XII is a rare genetic disease and can be considered a form of a Haemophilia. The genetic link was discovered when some family members also were found to be deficient in this liver manufactured protein.

Are you developing an understanding as to why chronic liver failure patients develop clotting and coagulation disorders??

More on this system in our next edition.