The Sense of Taste

The 2000-10000 taste buds of the tongue are the specialized taste organs. There are four types of taste buds: fungiform in the front of the tongue, caliciform and foliated in the back, and filiforms, which are less developed. The taste buds are found not only the tongue, but the pharynx and palate as well. The buds contain groups of 10-12 taste cells. Chemoreceptors are found in the taste cells, and are ordered in each bud in a similar fashion as segments of an orange, that is, oriented so that one pore is in the surface of the tongue and is not covered by its epithelium.

The taste cells are bipolar epithelial cells that renew every 10 days. The pole that is oriented towards the oral cavity has a membrane with tiny hairs that contain the taste chemoreceptors. It seems that certain parts of the tongue are more specialized for a certain flavor: sweetness in the point, salty and acidic in the lateral and sour in the end. However, not all scientists agree with this assumption. The saliva plays an important role, dissolving and distributing the different chemical compounds present in the food and facilitating its access to the pores. Almost any chemical component can generate a taste, although there are traditionally 4 basic groups: sweet, acid, salty and sour. To this end, the opposite pole of the taste cells connect with the synapse of neurons that send the nerve impulse. The nervous fibers that collect the taste cell-stimuli are 3 cranial nerves: taste (cranial nºVII), glossopharyngeal (cranial nºIX) and vagus (cranial nºX). The 3 nerves converge in the nucleus of the solitary tract in the posterior part of the brain, where the vagus nerve also directs the messages from the intestines and digestive tubes. However, in food there is a combination of fundamental molecules and flavors that present many variations that give rise to a wide variety of taste sensations. It is considered that the most basic tastes are perceived by the brain not by one pack of neuronal fibers but of several neurons with different thresholds of excitation, although there is always a preference for one of the 4 basic tastes.