tailieunhanh - Chapter 030. Disorders of Smell, Taste, and Hearing (Part 1)

Harrison's Internal Medicine Chapter 30. Disorders of Smell, Taste, and Hearing Smell The sense of smell determines the flavor and palatability of food and drink and serves, along with the trigeminal system, as a monitor of inhaled chemicals, including dangerous substances such as natural gas, smoke, and air pollutants. Olfactory dysfunction affects ~1% of people under age 60 and more than half of the population beyond this age. Definitions Smell is the perception of odor by the nose. Taste is the perception of salty, sweet, sour, or bitter by the tongue. Related sensations during eating such as somatic sensations of coolness, warmth,. | Chapter 030. Disorders of Smell Taste and Hearing Part 1 Harrison s Internal Medicine Chapter 30. Disorders of Smell Taste and Hearing Smell The sense of smell determines the flavor and palatability of food and drink and serves along with the trigeminal system as a monitor of inhaled chemicals including dangerous substances such as natural gas smoke and air pollutants. Olfactory dysfunction affects 1 of people under age 60 and more than half of the population beyond this age. Definitions Smell is the perception of odor by the nose. Taste is the perception of salty sweet sour or bitter by the tongue. Related sensations during eating such as somatic sensations of coolness warmth and irritation are mediated through the trigeminal glossopharyngeal and vagal afferents in the nose oral cavity tongue pharynx and larynx. Flavor is the complex interaction of taste smell and somatic sensation. Terms relating to disorders of smell include anosmia an absence of the ability to smell hyposmia a decreased ability to smell hyperosmia an increased sensitivity to an odorant dysosmia distortion in the perception of an odor phantosmia perception of an odorant where none is present and agnosia inability to classify contrast or identify odor sensations verbally even though the ability to distinguish between odorants or to recognize them may be normal. An odor stimulus is referred to as an odorant. Each category of smell dysfunction can be further subclassified as total applying to all odorants or partial dysfunction of only select odorants . Physiology of Smell The olfactory epithelium is located in the superior part of the nasal cavities and is highly variable in its distribution between individuals. Over time the olfactory epithelium loses its homogeneity as small areas undergo metaplasia producing islands of respiratory-like epithelium. This process is thought to be secondary to insults from environmental toxins bacteria and viruses. The primary sensory neuron in the olfactory .