One of the first anecdotes I heard as an undergraduate was about taste buds being present around the anus. Since it was mentioned briefly in a lecture, there was no opportunity to discuss it further. Who made the discovery was not mentioned. I subsequently tried to find out more. As a postgraduate student, I mentioned it to a couple of colleagues. One said that he had also heard this but knew nothing more. Another wondered whether it might be salivary glands rather than taste buds. The salivary gland idea makes sense. Salivary glands would lubricate the anus, easing the passage of the faeces.
We are used to the idea of tasting food as it goes in. Apart from enjoying certain flavours, disliking others is particularly important. What tastes unpleasant is often also harmful. Such food is best spat out. Tasting spent food on the way out seems odd - if not pointless.
I recently discovered an article in New Scientist (Jan 27th 2024. No 3475) called Why are there taste receptors on our testicles? (What we used to call taste buds were referred to as taste receptors.) The article pointed out that taste receptors are present in the guts of rats. That is a finding made in the 1990s. Subsequent work found them in our guts also. Finding this spread of taste receptors - between mouth and anus - is not necessarily strange. All the parts mentioned so far belong to the gastrointestinal tract. Perhaps genes responsible for their formation are expressed randomly throughout. However, taste receptors are now known to be present in other organs and tissues not part of the gastrointestinal tract. They are present in the heart, brain, bladder, lungs, body fat and, as the article’s title implied, the testicles.
Our choice of words may be causing problems. I still use the old taste bud terminology. Using the term taste receptor may be no better. We associate taste with our mouths. It is a mental construct. It is something in our consciousness - a product of the mind/brain. They are neither taste buds nor taste receptors as such. They are, more generically, sensors. These sensors detect things about the body. They provide information that forms a basis for a physiological response. The nutritional and energy states of the body are perhaps what is detected. Instead of finding taste receptors throughout the body, sensors found more widely have a specialised role in the mouth. They give us information our minds experience as taste.
What began as an anecdote heard as an undergraduate student in the late 1970s now forms the basis for new ideas about the human body. It is an organism permeated with sensors monitoring itself in ways far more extensive than previously imagined.
