You may think that we've got a pretty good handle on which organs there are in the body by now, but it turns out that the final count is surprisingly contentious. Researchers at Karolinska Institutet in Sweden claim to have discovered a new sensory organ in the skin that's involved in pain detection and response.
For better or worse, the skin is very sensitive to the outside world. Previously, it's been believed that nociceptive sensory nerve endings in the skin are directly responsible for picking up pain sensations. But they might not be working alone, according to the team on the new study.
The Karolinska researchers have apparently discovered a new type of glial cell in the skin that are highly sensitive to thermal and mechanical pain sensations. Thermal, as you may have guessed, are those pain signals related to extreme heat or cold on the skin, while mechanical pain includes those from cuts, pricks or pressure.
These cells are arranged within the skin in a mesh-like structure, which the team is calling an organ. Activation of these cells appears to create an electrical impulse, which then triggers the nerve cells we already knew were there. That in turn triggers a reflex action – such as sharply removing your hand from a hot object – and the experience of pain.
The researchers also say they ran experiments where they blocked the organ, and the ability to feel mechanical pain decreased as a result. They haven't clarified whether that's in mice, humans or something else, but it could be a promising lead towards new targets for particular types of pain relief.
"Our study shows that sensitivity to pain does not occur only in the skin's nerve fibers, but also in this recently-discovered pain-sensitive organ," says Patrik Ernfors, chief investigator on the study. "The discovery changes our understanding of the cellular mechanisms of physical sensation and it may be of significance in the understanding of chronic pain."
Whether or not this new body part officially joins the ranks as an organ remains to be seen. The definition can be fluid, depending on who you ask, and the argument was dredged up last year when the interstitium was discovered. That anatomical feature is made up of a complex series of interconnected cavities that help drain fluids into the lymphatic system. While the researchers called it a new organ, other scientists disagreed, likening them to blood vessels as components that are present throughout the body but don't fit the "organ" label.
Either way, the discovery of this new arrangement of pain-sensitive cells helps improve our understanding of how our body registers sensations, and could lead to new ways to treat chronic pain.
The research was published in the journal Science.
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