This Tuesday morning I’ve had the delight of musing about our incredible gut and how this organ exemplifies the old adage in biology that “structure defines function”.

Our bodies are full of other examples of this: our opposable thumbs allow us to grasp items large and small, our lengths of blood vessels in the cardiovascular system permit the distribution of oxygen and nutrients throughout our tissues, and the distinct structure of our neurons (brain cells) with their axons and dendrites begets an efficiency of intercellular communication that is the basis of memory, thought, and emotion.

When it comes to the gut, the beauty of its structure and function is often under-appreciated.

The gut is a dynamic and adaptable interface with the outside world. No other organ must take the foreign, alien environment outside the body and delicately separate out our basic life nourishment from that which may kill us. It is no wonder why there is so much potential for mishaps and mistakes as our immune system tries to determine what is friend or foe and the cells of the gut (enterocytes) seek out the carbohydrates, fats, and proteins that every part of our body needs to stay alive.

The population of trillions of microbes living inside our gut needs to be regularly sampled by dendritic cells (immune system surveillance cells) by way of the latter’s tentacle-like protrusions that squeeze their way through tight junctions (spaces between enterocytes). When a dendritic cell encounters even one pathogenic organism, a cascade of phosphorylations (the transfer of phosphates in cell signaling) act as alarm bells and can set off an immune response. White blood cells called macrophages and neutrophils then rush to the scene to protect against that pathogenic organism and can leave a wake of tissue damage in the intestinal barrier, damage which permits the leakage of bacterial organisms and food particles across that barrier and which necessitates further immune response.

This complex emergence of function from the shape and structure of the gut system is nothing short of beautiful. When we consider serious conditions involving the inner-workings of the gut such as Inflammatory Bowel Disease, we can look to the very structure of the gut system and accordingly match our interventions to restore function. A single medication, probiotic, or diet alone is generally no match for the vast complexity of biology, but a nuanced, comprehensive, and community-based approach that leverages all the available science may stand a chance.

 

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