The nasal cavity and its olfactory sensory territories

Citation: Salazar I (2015) The nasal cavity and its olfactory sensory territories. The sense of smell is more complex than previously believed. For different reasons, the receptors traditionally thought of having the ability to identify chemical olfactory signals were exclusively confined to the epithelium of the mucosa lining both the posterior part of the walls of the nasal cavity and the ethmoturbinates. However, at the end of the nineteenth century, the vomeronasal organ (VNO) was demonstrated to have its own sensory epithelium, able to perform a similar function (Retzius, 1894). In later years, a small and isolated area of olfactory epithelium was detected in the nasal septum (Rodolfo-Masera, 1943); this structure was denominated septal organ. Later evidence showed than a group of cells located on the superior and anterior part of the nasal vestibuli (Grüneberg, 1973) also had a functional role within the olfactory system (Fuss et al., 2005). These findings led to being currently accepted that in certain macrosmatic animals the olfactory sensory receptors are located in four different regions of the nasal cavity: the main olfactory epithelium (MOE), the vomeronasal epithelium (VnE), the septal organ (SO), and the ganglion of Grüneberg (GG). Besides, a subdivision of both the MOE and the VnE can be done into four and two areas respectively. Following a morphological criterion four/eight structures integrate the olfactory subsystems (OSbS) (Breer et al., 2006). However, the axonal projections of those structures onto the olfactory bulb have been observed to show overlapping (Munger et al., 2009), and the concept of OSbS should be limited to the morphological location of the mentioned structures. That point of view has been used in this Research topic. To begin to understand the sense of smell as a whole in the mammalian class, one of the biggest challenges we are confronted with is to find answers to some basic and critical questions as, for instance: what are exactly the GG, the VNO and the SO, and what are their precise functions? How are the connections between them and how does each of them interact with the MOE? What happens if one or more than one of such structures is absent in a particular species? From an evolutionary perspective, it is reasonable to assume that partial or total response to these questions and others can be found, but it would require having the genome of the species, and a deep knowledge of the …