Quantitative changes in taste sensations
In pathological physiology, several typical forms are distinguished in which specifically the strength (intensity) of taste perception changes. These include ageusia, hypogeusia, and hypergeusia.
- Ageusia is a typical form of disorder characterized by the absolute absence of taste sensations. A patient with ageusia is completely incapable of recognizing the taste of food.
- Hypogeusia is a condition in which taste sensations are present, but their acuity is pathologically reduced.
- Hypergeusia is a typical form of taste disorder manifested by a pathological increase in taste sensations. It is important to note that in hypergeusia, the subjective sensation is completely inadequate to the real strength of the stimulus.
Etiology of hypergeusia: The most frequent cause of this condition is hypersensitization (increased sensitivity) of taste receptors located in the oral cavity. Classical examples of the pathophysiological mechanisms of hypersensitization include a violation of the acid-base state (ABS) of the interstitial fluid in the tissues of the tongue, as well as dysionia (disturbance of the normal ionic composition) of saliva, which is often observed in various stomatitis.
Qualitative distortions and taste perversions
In addition to quantitative changes, there are typical disorders in which a false or perverted perception is formed.
- Parageusia is a typical taste disorder characterized by a qualitative difference between the subjective taste sensation and the normal one. In the clinical picture, this manifests as an ordinary substance being perceived by the patient in a completely distorted manner, forming a false sense of taste. Classical examples of parageusia: a sour substance is perceived by a person as bitter, sweet food seems salty, and an objectively bitter taste is felt as sour.
- Dysgeusia is a more severe typical form of disorder manifested by a pathological change and deep perversion of not only the taste sensations themselves, but also the patient's taste preferences. The clinical picture of dysgeusia is extremely specific: a person begins to actively consume spoiled products or completely non-food objects that pose a direct danger to health. Examples of such eating behavior include eating grass, paper, sand, or excrement.
Etiology of parageusign and dysgeusias: Unlike hypergeusia, where the problem lies at the receptor level, the main cause of qualitative taste distortions is damage to the central nervous structures involved in the formation of taste sensations. Such pathologies are typical for diseases such as encephalitis, schizophrenia, and various neuroses.
Impact on appetite and general consequences for the body
Taste disorders never pass without a trace for the body. Their main consequences include pathological changes in appetite, serious disruptions of digestive processes, and, consequently, changes in body weight (it can become either insufficient or excessive compared to the physiological norm).
Since taste is closely related to eating behavior, it is necessary to consider the concept of appetite. Appetite is a subjective sensation directly related to the body's need for a certain quality and quantity of food.
In pathophysiology, the following typical forms of appetite disorders are distinguished:
- Anorexia (the term originates from the Greek word Orexis, meaning "appetite") is a typical form of disorder characterized by a complete lack of appetite.
- Hyporexia is a condition characterized by a marked decrease in appetite.
- Hyperrexia is a pathological increase in appetite, forcing a person to consume an excessive amount of food.
- Pararexia is a perversion of appetite that often accompanies dysgeusia and forces the patient to seek atypical or inedible objects to satisfy nutritional needs.
Briefly: answers to topical questions
Which cranial nerves provide taste innervation of the tongue?
Taste innervation of the tongue is provided by sensory fibers of three pairs of cranial nerves.
- Facial nerve (n. facialis, Pair VII) — innervates the anterior 2/3 of the tongue via its branch, the chorda tympani (chorda tympani).
- Glossopharyngeal nerve (n. glossopharyngeus, IX pair) provides taste sensitivity of the posterior third of the tongue, as well as vallate papillae (papillae vallatae).
- Vagus nerve (n. vagus, X pair) carries taste fibers predominantly from the most posterior sections and the root of the tongue (near the epiglottis).
The cell bodies of neurons belonging to the taste fibers of these cranial nerves are located in their respective sensory ganglia, and their axons are directed into the brainstem to the nucleus of the solitary tract.
Where is the cortical end of the gustatory analyzer located?
The cortical end of the gustatory analyzer is located in the uncus (uncus) of the limbic lobe of the cerebral cortex.
Which types of tongue papillae contain taste buds?
Taste buds contain three types of tongue papillae, the epithelium of which is stratified squamous non-keratinized.
- Fungiform papillae (papillae fungiformes) are scattered among filiform papillae at the apex and edges of the tongue; taste buds occur irregularly in the epithelium of their apex.
- Foliate papillae (papillae foliatae) are represented by folds of the mucous membrane along the lateral edges of the tongue; receptors are located in the epithelium of the lateral surface of these papillae.
- Vallate papillae (papillae vallatae) are the largest formations at the border of the root and body of the tongue; they contain up to half of all taste buds located on their side walls and adjacent surface of the mound.
Filiform and conical papillae perform an exclusively mechanical function and do not have taste buds.
To easily memorize terms, focus on the prefixes: A-geusia (negation — complete absence of taste), Hypo-geusia (decrease), Hyper-geusia (excessive enhancement), Para-geusia (near/past — false perception of ordinary foods), Dys-geusia (gross disturbance — craving for the inedible).
Class and exam questions
How does parageusia fundamentally differ from dysgeusia?
In parageusia, the perception of ordinary substances is distorted (e.g., sweet tastes salty, and sour tastes bitter). In dysgeusia, taste preferences themselves are perverted: the patient begins to consume dangerous non-food items (sand, paper, feces) or spoiled products.
What is the etiology of hypergeusia?
The most frequent cause is hypersensitization (increased sensitivity) of taste receptors in the oral cavity. This can occur due to a violation of the acid-base state of the tongue's interstitial fluid or saliva dysionia against the background of stomatitis.
What pathologies cause qualitative taste disorders?
Parageusias and dysgeusias most often develop when central nervous structures involved in the formation of taste sensations are damaged. The main pathologies leading to this are encephalitis, schizophrenia, and neuroses.
How do taste disorders affect appetite?
They cause typical appetite disorders: anorexia (complete absence), hyporexia (decrease), hyperrexia (pathological increase), or pararexia (perversion). Ultimately, this leads to digestive disorders and changes in body weight.
What else to study on this topic
- Mechanisms of hypersensitization of oral taste receptors
- Saliva dysionia in stomatitis and its effect on digestion
- Pathogenesis of central taste disorders in schizophrenia and neuroses
- Relationship between dysgeusia and pararexia
- The effect of the acid-base state on the interstitial fluid of the tongue
Master the entire topic in the "Pathophysiology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Taste disorders" and another 4,913 pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 135 video lessons on the subject
Other topics in "Chapter 24. Typical Forms of Digestive System Pathology"
Free video lessons: pathophysiologyShort lessons with lecture notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.