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Tastant molecule
any substance capable of stimulating the sense of taste
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Papillae
- 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.
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Filiform papillae
- 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.
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Fungiform papillae
- 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.
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Foliate papillae
these are ridges and grooves towards the posterior part of the tongue found on lateral margins.
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Circumvallate papillae
- 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.
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Taste bud
- structure on the tongue that contains several taste receptor cells.
- A young tongue contains ~10,000 taste buds.
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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).
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Microvilli
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
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Taste pore
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.
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Supertasters
- 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
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Gustatory nerves
- 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).
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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
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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).
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Flavor
- 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.
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Gustatory map
cortical representation of the different taste modalities; recent research shows a gustatory map in the right insula
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Disorders of taste:
- Ageusia
- Hypogeusia
- Dysgeusia
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Ageusia
the complete loss of taste; patients will not be able to discriminate differences among sweetness, sourness, bitterness, saltiness, and umami
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Hypogeusia
partial loss of taste; taste sensitivity is reduced
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Dysgeusia
- 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.
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Disorders of the tongue
- Geographical tongue
- Fissured tongue
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Geographical 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
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Fissured tongue
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
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