The sense of smell, its signalling pathways, and the dichotomy of cilia and microvilli in olfactory sensory cells

Smell is often regarded as an ancillary perception in primates, who seem so dominated by their sense of vision. In this paper, we will portray some aspects of the significance of olfaction to human life and speculate on what evolutionary factors contribute to keeping it alive. We then outline the functional architecture of olfactory sensory neurons and their signal transduction pathways, which are the primary detectors that render olfactory perception possible. Throughout the phylogenetic tree, olfactory neurons, at their apical tip, are either decorated with cilia or with microvilli. The significance of this dichotomy is unknown. It is generally assumed that mammalian olfactory neurons are of the ciliary type only. The existance of so-called olfactory microvillar cells in mammals, however, is well documented, but their nature remains unclear and their function orphaned. This paper discusses the possibility, that in the main olfactory epithelium of mammals ciliated and microvillar sensory cells exist concurrently. We review evidence related to this hypothesis and ask, what function olfactory microvillar cells might have and what signalling mechanisms they use

Upper aerodigestive tract cancer: summary of the National Institute for Health and Care Excellence guidelines for England and Wales.

The cancers of the upper aerodigestive tract (CUADT) considered in this guideline document include the oral cavity, oropharynx, nasopharynx, hypopharynx, larynx and paranasal sinus. Squamous cell carcinomas (SCC) are the predominant (91%) histological type of malignancies seen at these sites,with approximately 8500 people per annum being diagnosed with CUADT in England and Wales. This guideline deals with SCC and mucosal melanoma and applies to 94% of CUADT cancers. Between 1990 and 2006, the incidence of oropharyngeal cancer has doubled, oral cavity cancer showed a slight increase, whilst cases of larynx cancer have declined.1 Although the age and sex distribution varies across primary sites, SCCs are commoner in men with incidence starting at the age of 40, and peaking after the age of 60. The aetiologic factors associated with CUADT are smoking, alcohol, human papillomavirus (oropharynx only) and certain occupations.</p