AP help- Intrinsic/Extrinsic pathways

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Can anyone help me understand the intrinsic and extrinsic pathways of the coagulation cascade? I've read the section in my textbook several times and for some reason it's just not sinking in. I was hoping that someone might be able to explain it in another way that might click with me.

I guess what I'm getting confused on is generally what is the difference between the two? Is it situational? Meaning does it depend on what causes the need for the clotting to begin with that determines the pathway? I feel like an idiot for being so confused :confused:

For reference, this is what the text says:

Intrinsic Pathway:

  • Triggered by negatively charged surfaces such as activated platelets, collagen, or glass.
  • Called intrinsic because the clotting factors are present within the blood.

Extrinsic Pathway:

  • Triggered by exposing blood to a factor found in tissues underneath the damaged endothelium. This factor is called tissue factor (TF).
  • Called extrinsic because the tissure factor it requires is found outside of the blood.

I guess I just need a "dumbed down" very basic explanation lol.

Thanks to anyone that can help!

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If you google "intrinsic extrinsic coagulation pathway" and then click on "videos", you'll get lots of help.

I found that with physiology, watching various youtube videos was a great help to give me different perspectives and help me to understand better.

Here's a good example:

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