The following are essential components of the intrinsic coagulation system -a) Pre-kallikreinb) High molecular weight kininogenc) Factor VIId) Tissue factore) Factor X
## **Core Concept**
The intrinsic coagulation pathway is a complex cascade of enzymatic reactions that leads to the formation of a blood clot. It is one of the three pathways that activate the coagulation cascade, the others being the extrinsic and common pathways. The intrinsic pathway is activated by internal factors within the blood itself.
## **Why the Correct Answer is Right**
The intrinsic coagulation system involves several key components:
- **Pre-kallikrein** and **High molecular weight kininogen** are crucial as they are part of the contact activation system which initiates the intrinsic pathway. Pre-kallikrein is converted to kallikrein, which then activates Factor XII.
- **Factor VII** is actually a part of the extrinsic pathway when activated by tissue factor. However, its inactive form, not the activated one, isn't exclusively part of the intrinsic pathway but can interact in a broader coagulation context.
- **Tissue factor** is a key initiator of the extrinsic pathway, not the intrinsic pathway.
- **Factor X** is a critical component of the common coagulation pathway, which is activated by both the intrinsic and extrinsic pathways.
## **Why Each Wrong Option is Incorrect**
- **Option C (c, d, e):** This option includes Factor VII, tissue factor, and Factor X. Factor VII and tissue factor are primarily associated with the extrinsic pathway, not the intrinsic pathway. Factor X, while crucial for coagulation, is part of the common pathway.
- **Option D (a, b, c, d):** This option incorrectly includes Factor VII and tissue factor, which are not components of the intrinsic pathway.
- **Option B (b, c, d, e):** This option incorrectly includes Factor VII, tissue factor, and does not accurately represent the intrinsic pathway components.
- **Option A (a, b):** This option only includes pre-kallikrein and high molecular weight kininogen, missing other essential components but not incorrectly including extrinsic pathway components.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the intrinsic pathway is activated by factors within the blood and involves factors XII, XI, IX, VIII, X, V, II (prothrombin), and fibrinogen. Pre-kallikrein and high molecular weight kininogen play roles in the initiation of this pathway through the contact activation system.
## **Correct Answer:** .