What do the tongue papillae contain

Each taste bud is innervated by 50 nerve fibres which connect up to five taste buds each. However, if the nerve regenerates, the surrounding cells become organised into new taste buds; this is attributed to the influence of a chemical inductive from the redeveloping nerve fibre. The chorda tympani is a branch of the facial nerve which innervates the taste buds on the anterior two-thirds of the tongue, while the posterior third of the tongue and taste buds situated in other areas i.

From the nucleus tractus solitarius , the neurons relay into the medial lemniscus of the medulla oblongata. The axons of these second-order neurons then transmit directly to the ventral posteromedial nucleus of the thalamus where they travel via thalamic radiation to the anterior part of the ipsilateral insula which facilitates conscious perception of taste and taste discrimination [ Figure 1B ].

Previously, it was believed that different areas of the tongue were responsible for perceiving the five different categories of taste sweet, salty, bitter, sour and umami. Flavours are identified as a result of a backdrop of complex chemical mechanisms which involve ionic exchange through specific channels and secondary messenger activity. Supertaster phenomenon refers to the existence of individuals who experience tastes with far greater intensity than normal, to the degree that they can perceive usually tasteless substances, such as phenylthiocarbamide PTC and propylthiouracil PROP.

This concept was first described by Fox in when it was noted that PTC was tasteless to some individuals, yet perceived as bitter by others. In recent years, research has revealed that this phenomenon is genetic in nature. Nasri-Heir et al. The papillae within these boxes were then counted and averaged to arrive at a mean value. Image of fungiform papillae quantification using digital photography and computer software. Reproduced with permission from Khan et al.

Pavlos et al. The fungiform papillae were easily distinguishable as they were lightly stained in comparison to the darker filiform papillae. Zhang et al. Photographs of tongue stained with brilliant blue FCF before A and after B fungiform papillae quantification. Reproduced with permission from Jilani et al.

Nuessle et al. Using image analysis software and digital photography, the fungiform papillae were then characterised based on their shape, colour, size and height.

Eldeghaidy et al. However, one limitation of this methodology is that the software may inaccurately assess the diameter of the papillae because the software considers all fungiform papillae to be exactly circular in shape. Nutrition and age are two major factors that affect the number of papillae present on the dorsum of the tongue. Zinc deficiency can also have similar consequences. Due to their high metabolic activity, cells forming filiform and fungiform papillae are also sensitive to enzyme, circulation or nutrient disturbances which can lead to atrophy.

During atrophy, filiform papillae are more vulnerable to such disturbances compared to fungiform papillae ; moreover, following atrophy, fungiform papillae regenerate faster in comparison to filiform papillae.

Factors potentially resulting in lingual papillae loss Drugs that interfere with the growth and maturation of the epithelium e. The two primary methods of evaluating taste sensation are chemogustometry and electrogustometry. Chemogustometry involves the application of chemical solutions to the oral mucosa ; subsequently, the degree to which any of the five types of taste presents itself is evaluated by equating the taste with that of a reference material.

This is done systematically by either increasing or decreasing the dilution of the substance. Water is used as a control during the process, with the subject ideally being able to discriminate between water and the diluted test solution. Bitterness is detected by the action of the bitter substance on TAS2R receptors, a type of G protein-linked receptor. Taste transduction is thus induced by the influx of sodium ions in the ENaC receptors which facilitates the release of glutamate to depolarise neurons.

Sourness, measured using diluted hydrochloric acid, also acts via the ENaC receptors which allow the inflow of protons and triggers neurons. Sweetness is assessed using a diluted sweet substance such as sucrose or artificial sweeteners like saccharin, which differ in taste due to their distinct chemical structures. Taste transduction occurs via another G protein receptor known as taste receptor 1.

The final type of taste, umami , is savoury in nature. Umami taste is induced by the activation of meta-botropic glutamate receptor 4 as a result of stimulants such as monosodium glutamate. Inosine monophosphate and guanosine monophosphate act as agonists during umami taste induction. One method of chemogustometric evaluation involves presenting tastants to subjects in a clinical setting via soaked elongated strips or circular disks.

Such strips or disks are dissolvable in the oral cavity and do not need to be retrieved afterwards. Using this method, three drops of a chemical tasting solution are placed in the middle of the dorsum of the tongue, approximately 1. Event-related potentials refer to the electrical responses evoked in the brain when an individual is presented with a stimulus. As such, after applying chemical gustatory stimuli to the tongue, electroencephalography can show cortical brain activity associated with the taste sensation, along with its topographical distribution.

Chemogustometry consists of using an array of chemical solutions in multiple concentrations to assess taste sensation. Some advantages of this method include the long shelf-life of the materials needed, the ease of administration, the rapidity of testing and the fact that this method allows for evaluation of each side of the tongue separately. Electrogustometry quantifies taste and measures the threshold of taste sensation by passing a controlled current through the tongue using electrodes.

As cathodal stimuli do not produce any significant recordable sensation, a weak anodal current is used. When an electrode from an electrogustometer is placed on tongue, two types of sensations are induced—tingling and taste. Therefore, electrogustometry aids in differentiating between the chorda tympani and lingual nerves and is especially important in determining the integrity of the neural pathway.

Electrogustometry is a quick and quantitative tool to assess taste threshold, particularly among patients with taste disorders such as hemiageusia and ageusia. Furthermore, electrogustometry can also aid in determining patient prognosis. However, a major drawback of electrogustometry is that it is subjective and relies on feedback from the subject.

Finally, this technique cannot be used for patients with artificial pacemakers as electrical stimuli from the electrodes may cause interference with electrical signals from the pacemaker.

Braud et al. Ovesen et al. These findings indicate that electrogustometry could be a useful diagnostic tool in neoplastic cancers. Epstein et al. As such, it is recommended that taste and olfactory electrogustometric evaluations be made mandatory for all patients undergoing cancer treatment. Dzaman et al. Doty et al. The researchers reported a deterioration in taste sensitivity commencing in middle age and progressively reducing after 50 years of age. Boucher et al. Depressed or altered taste sensation has been reported among chronic smokers.

These not only topically affect taste receptors cells and impede the normal mechanism of taste conduction but also affect the neurological transmission of taste sensations. Using a modified form of electrogustometry, Khan et al. The researchers advocated for the use of electrogustometry as a method of motivating chronic smokers to stop smoking. But as a person ages, some of those taste cells don't get replaced. An older person may only have 5, working taste buds.

That's why certain foods may taste stronger to you than they do to adults. Smoking also can reduce the number of taste buds a person has. But before you give taste buds all the credit for your favorite flavors, it's important to thank your nose.

Olfactory say: ahl-FAK-tuh-ree receptors inside the uppermost part of the nose contain special cells that help you smell.

They send messages to the brain. Here's how it works: While you're chewing, the food releases chemicals that immediately travel up into your nose. These chemicals trigger the olfactory receptors inside the nose. Our Mission. Contact Us.

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Learn more about our commitment to oral health education. Fungiform Papillae and Your Tongue. Top Articles. Papillae: Form and Function Papillae are the tiny raised protrusions on the tongue that contain taste buds. The Life of a Papilla The cells of the papillae are continually regenerated — about every two weeks or so.