FUNGIFORM PAPILLAE: CHARACTERISTICS, FUNCTIONS, STRUCTURE - BIOLOGY - 2025

The fungiform papillae are mushroom - shaped projections that are presented on the dorsal surface of the tongue. Due to the multiple blood vessels that supply them, they are generally pink or red. They are visible to the human eye, especially after drinking milk or placing a drop of food coloring on the tip of the tongue.

There are from 200 to 400 fungiform papillae spread throughout the league, although they are densely grouped in the anterior lingual area, at the tip and to the sides, in the so-called V lingual. 87% of these papillae are located up to approximately 2 cm from the tip of the tongue, being very scarce in the posterior part.

By Antimoni (Derivative work of the user Antimoni), via Wikimedia Commons

The fungiform papillae contain the taste-sensitive receptor cells, which form the structures that make up the taste buds on the surface of the papilla.

These taste buds can distinguish the five flavors: sweet, sour, bitter, salty, and umami. The ancient supposed existence of a map of flavors in the language, today is considered one of the greatest sensory myths, and has already been discarded.

characteristics

Shape

The fungiform papillae are raised structures that protrude from the lingual surface, with a characteristic shape of a mushroom. They have a diameter of up to 15 mm.

Location and number

They spread between the filiform papillae throughout the anterior third of the tongue, presenting greater density towards the tip.

The average number of fungiform papillae on the tongue is around 200, most densely located in the anterior two cm of the tip of the tongue.

Semi diagrammatic view of a portion of the mucosa of the tongue. Two fungiform papillae (mushroom-shaped) are shown between several filiform papillae.

In humans, fungiform papillae contain from 3 to 20 or more taste buds, emerging at the top of each papilla, although some fungiform papillae, about 60%, may lack taste buds.

On average, the human tongue can contain 2,000 to 8,000 taste buds, varying according to various factors.

There are reports that suggest that women have, on average, more fungiform papillae than men, increasing their sense of taste. However, there are conflicting results for this claim.

It has also been reported that there is a significantly higher density of fungiform papillae in children than in adults, which has led to the conclusion that fungiform papillae atrophy with age.

These papillae are more stimulated in childhood and old age. They are innervated by a branch of the facial nerve, called the chorda tympani, which is attached to the lingual nerve for most of its course.

Structure

The fungiform papillae have a nucleus of connective tissue and are innervated by the seventh cranial nerve, more specifically through the submandibular ganglion, the chorda tympani nerve, and the geniculate ganglion, which ascends to the solitary nucleus in the brainstem.

Taste buds

Human mushroom papillae contain from zero to more than 25 taste buds, although more than half of them do not have taste buds.

Each of these taste buds contains between 50 to 100 cells, of four morphologically and functionally distinct types, that exhibit neuronal and epithelial cell properties.

About half of the cells in the taste bud are spindle cells type I (dark), which appear to have a similar function to the glia, because they surround other types of cells and express molecules involved in the inactivation of neurotransmitters.

In studies to determine three-dimensional structure, the connective tissue of the fungiform papillae shows a coral-shaped structure, with numerous small rod-shaped protrusions on the lateral surfaces, and in the upper part it has branched flat areas with some small depressions round that house the taste buds.

Mechanoreceptors

The fungiform papillae have in their structure, in addition to the taste buds, the mechanoreceptors. They are primary sensory structures that collect information on the mechanical features of the environment and the particles with which they come into contact.

The entire structure is innervated by the fibers of the taste nerve and the trigeminal nerve. Due to this structure, it has been suggested that fungiform papillae, in addition to being associated with taste, are also responsible for part of oral sensitivity.

Function

The fungiform papillae represent the true organ of taste. They detect the flavors as well as the temperature and the touch of the particles that make up the food.

Sensory cells

Each taste bud has between 10 and 50 sensory cells, which in turn are connected to many different nerve fibers. These sensory cells are renewed once a week.

The sensory epithelial cells of the fungiform papillae form, together with other supporting cells, a special structure, resembling a bud or capsule, somewhat resembling an orange or an onion, with their sections arranged around a center.

At the tip of this capsule there is a pore, a small indentation, that works like a funnel filled with liquid. In the cleft of the funnel there are numerous extensions of the sensory cells, thin and elongated.

Chemicals responsible for flavor are moistened in this funnel-like hole. Proteins on the surface of cell extensions bind to chemicals for tasting. This ensures that the substances are detected and analyzed by as many sensory cells as possible before being swallowed.

Schematic diagram of a taste bud.

Towards the nervous system

The final step in perceiving taste is the transfer of the perceived sensation to the nervous system. This is done by several cranial nerves, which carry all the information to a part of the lower section of the brainstem.

At that point there is a split: some fibers carry taste signals along with signals from other sensory perceptions such as pain, temperature, or contact through various points of exchange with consciousness.

The other fibers bypass these exchange points of conscious perception and lead directly to the parts of the brain that are connected to sensory perception and that are responsible for ensuring our survival. This is where taste signals are combined with different odor signals.

Disorders associated with fungiform pupils

There are reports of various factors related to changes in the density of the fungiform papillae, such as age, sex, smoking, alcohol consumption and regular exposure to organic solvents.

These changes in the number of fungiform papillae present in the lingual epithelium can be associated with various taste disorders, but usually none of them merit a danger to the health of the subject.

Certain neurotrophic factors, known as neurotrophins, appear to play a critical role in the development of fungiform papillae and taste buds.

In this sense, several neurological disorders show among their symptoms a decrease or an increase in the number of fungiform papillae. They can be grouped into two main types:

Disorders with reduced papillae

Such as Machado-Joseph disease, Stüve-Wiedemann syndrome, familial dysautonomia, muscular dystonia, and Behçet's disease.

Disorders with only taste defects

Such as Alzheimer's disease, Huntington's disease, type IV hereditary sensory and autonomic neuropathy, and diabetes mellitus.

Parkinson's disease has also been reported to produce an increased taste sensation.

Atrophic glossitis

Atrophic glossitis is a condition characterized by the absence of filiform or fungiform papillae on the dorsal surface of the tongue. Consequently, the ordinary texture and appearance of the dorsal tongue, determined by the papillary protrusion, becomes a smooth-looking epithelium.

Several etiological factors have been correlated with papillary atrophy, such as congenital or developmental conditions, infections, neoplasms, metabolic disorders, blood dyscrasias, and immune diseases.

Atrophic glossitis has also been correlated with protein deficiency and a hypocaloric diet; as well as iron, vitamin B12, folic acid, riboflavin and niacin deficiencies.

References

1. Cheng LHH, Robinson PP (1991). The distribution of fungiform papillae and taste buds on the human tongue. Arch. Oral Biol., 36 (8): 583-589
2. Erriu, M., Pili, FMG, Cadoni, S., & Garau, V. (2016). Diagnosis of Lingual Atrophic Conditions: Associations with Local and Systemic Factors. A Descriptive Review. The Open Dentistry Journal, 10: 619–635.
3. Gravina S., Yep G., Khan M. (2013) Human Biology of Taste. Annals of Saudi Medicine. 33: 217-222.
4. Zhang GH, Zhang HY, Wang XF, Zhan YH, Deng SP, Qin YM (2009) The Relationship between Fungiform Papillae Density and Detection Threshold for Sucrose in the Young Males, Chemical Senses, 34 (1): 93–99.
5. Fungiform Papillae (2009). In: Binder MD, Hirokawa N., Windhorst U. (eds). Encyclopedia of Neuroscience. Springer, Berlin, Heidelberg.
6. How does our sense of taste work? Available at: ncbi.nlm.nih.gov