tailieunhanh - Chapter 030. Disorders of Smell, Taste, and Hearing

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. | Chapter 030. Disorders of Smell Taste and Hearing 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 SmellThe 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 epithelium is the bipolar cell. The dendritic process of the bipolar cell has a bulb-shaped vesicle that projects into the mucous layer and bears six to eight cilia containing odorant receptors. On average each bipolar cell elaborates 56 cm2 9 of surface area to receive olfactory stimuli. These primary sensory neurons are unique among sensory systems in that they are short-lived regularly replaced and regenerate and establish new central connections after injury. Basal stem cells located on the basal surface of the olfactory epithelium are the .