any substance capable of stimulating the sense of taste
- The majority of taste buds on the tongue sit on raised protrusions of the tongue surface called papillae.
- papilla = singular form
- papillae = plural form
- There are four types of papillae present in the human tongue.
- These types differ by shape, location on tongue, and location of taste buds within a papilla.
- these are thin, long papillae "V"-shaped cones that don't contain taste buds but are the most numerous.
- These papillae are mechanical and not involved in gustation.
- as the name suggests, these are slightly mushroom-shaped if looked at in section.
- these are present mostly at the apex (tip) of the tongue, as well as at the sides.
these are ridges and grooves towards the posterior part of the tongue found on lateral margins.
- there are only about 3-14 of these papillae on most people, and they are present at the back of the oral part of the tongue.
- They are arranged in a circular-shaped row just in front of the sulcus terminalis of the tongue.
- structure on the tongue that contains several taste receptor cells.
- A young tongue contains ~10,000 taste buds.
Taste receptor cells
- provide taste information.
- They are located throughout the tongue in the taste buds, have areas of higher sensitivity, and have a very short life span (i.e., they are replaced frequently with new taste cells).
microscopic cellular membrane protrusions that increase the surface area of cells and minimize any increase in volume and are involved in a wide variety of functions
any of numerous spherical clusters of receptor cells found mainly in the epithelium of the tongue and constituting the end organs of the sense of taste.
- people who have a genetic mutation producing extra fungiform papillae and an increase of gustatory nerve fibers per papilla.
- They therefore experience a greater intensity of taste than normal, and may be especially sensitive to bitter tastes and the texture of fat
- nerve fibers at each taste bud that receive information from the taste receptor cells.
- Their axons join three different cranial nerves to carry taste information to cortex (which cranial nerve depends on location in tongue and pharynx/throat).
Anterior insula & frontal operculum
- adjacent cortical regions involved in taste processing
- considered to be primary gustatory cortex. Plays a primary role in taste identification and evaluation of taste intensity
Orbitofrontal cortex for taste
- ventral region of the frontal lobes that is located just above the orbits of the eyes.
- Contains secondary gustatory cortex, which is involved in identifying taste, determining the reward value (e.g., pleasantness) of a taste, combining multisensory information to determine flavor, and signaling satiety (fullness).
- The perception of flavor is a multisensory experience, which relies on the integration of cues from most of the human senses.
- The process of flavor perception involves the complex interaction of taste with the smell, texture (from S1), and sight of food.
- In addition, flavor perception changes over time during a meal to signal satiety – or fullness.
cortical representation of the different taste modalities; recent research shows a gustatory map in the right insula
Disorders of taste:
the complete loss of taste; patients will not be able to discriminate differences among sweetness, sourness, bitterness, saltiness, and umami
partial loss of taste; taste sensitivity is reduced
- distortion or alteration of taste; food tastes abnormal
- Causes of ageusia, hypogeusia, dysgeusia – medication side effects, vitamin deficiencies, and respiratory illnesses with clogged nasal sinuses are common causes of dysgeusia and hypogeusia. Trauma is a common cause of ageusia.
Disorders of the tongue
- Geographical tongue
- Fissured tongue
an inflammatory condition of the mucous membrane of the tongue in which the loss of fungiform papillae produce smooth, red, painful regions that change location over time; May result from other infections or medications like antibiotics
benign condition characterized by deep grooves (fissures) in the top surface of the tongue; associated with geographical tongue, aging, environmental factors, and genetic conditions like Down’s syndrome