Official Step 1 HY Gastroenterology Concepts & Discussion Thread

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In FA 2014, zone 1 of the liver is most affected by ingested toxins (at least that's my interpretation) and zone 3 contains the cyp450 system and is most sensitive to metabolic toxins.

So if ingested toxins are metabolized by the cyp450 system why would't zone 3 be affected as opposed to zone 1?
 
Ingested toxins hit zone 1 because that's the first region of the liver architecture that receives blood and the highest concentration of toxins. However, there are not a lot of cyp 450 enzymes here to metabolize the toxins. Hence toxins can wreak havoc in zone 1. In zone 3, there is much more cyp 450 enzymes, and so the bulk of detoxifying occurs here.
 
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