Our gastrointestinal system is filled with regulatory molecules that place brakes in the absorption process. For instance, the food that we consume daily is filled with harmful substances that our body does not absorb, and these substances are later excreted. However, when ingesting poison or a potentially poisonous substance at high quantities our gastrointestinal system ends up absorbing these poisonous substances in sufficient quantities (if present) to kill us. Why can't these regulatory mechanisms not entirely prevent the absorption of toxic/poisonous substances that can cause us harm or death?

  • $\begingroup$ Is there a specific substance you are thinking about? $\endgroup$ – Arsak Apr 6 at 4:43
  • $\begingroup$ regulating is not the same as control entirely, your skin is proof against many materials but DMSO or mercury pass right through it. $\endgroup$ – John Apr 6 at 13:02
  • $\begingroup$ Yes Arsak, any pharmaceutical drug, for instance Ibuprophen. If any person ingests enough Ibuprophen,the pharmaceutical will no longer be therapeutic, as it would get absorbed in sufficient quantity to cause toxicity. $\endgroup$ – mellamoleon Apr 6 at 17:20
  • $\begingroup$ Thanks for the insight John. However, the gastrointestinal tract, contrary to the skin is under more scrutiny in terms of absorption regulation. We rarely abosrb substances through the skin, but continuously need to regulate which substances are absorbed or excreted in the gastrointestinal tract. Hence, my question. Why can't the gastrointestinal put a momentary full stop on absorption, say for 2 hours. Is it so important for continual absorption to occur that it cannot be stopped? $\endgroup$ – mellamoleon Apr 6 at 17:23

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