Mechanisms of Olfaction - Bioelectronic Nose: Integration of Biotechnology and Nanotechnology - page 25

Fig. 2.1 Sagittal view of a mouse head. The anterio-dorsal tip contains the Grueneberg ganglion .
The VNO is located on the ventral side and is divided into 2 halves, each expressing a unique
receptor repertoire, which project to the accessory olfactory bulb located at the distal end of the
olfactory bulb. The dorsal receptors in the olfactory epithelium are depicted in red and the ventral
receptors in blue . The areas they project to on the olfactory bulb are labeled with the same colors .
The septal organ is shown at the ventral base of the nasal septum

2.3 Main Olfactory Epithelium

2.3.1 Anatomy

Neurons responsible for the detection of odors from the environment are found in
the olfactory epithelium (OE) located in the dorso-caudal nasal vault along the up-
per portion of the nasal septum, cribriform plate and the medial wall of the superior
turbinate from where they project their dendrites into the nasal passage. These ol-
factory sensory neurons (OSNs) lie in a pseudostratified columnar epithelium along
with supporting cells (sustentacular cells), microvillar cells and basal cells [ 24 ].
The epithelium lies on top of a highly vascular lamina propia, which contains the
Bowman's gland. Basal cells are stem cells responsible for the replacement of the
OSNs and the Bowman's gland is responsible for secreting the serous component
of the mucous layer covering the OE [ 25 ]. OSNs form a dendritic knob at the junc-
tion between the tissue and the nasal passage from which 5 to 20 cilia emerge; these
cilia are bathed in the mucus in which odor molecules dissolve and then come in
contact with the OR [ 26 ]. These cilia lack dynein and therefore do not exhibit any
motility. Their main advantage is to increase the surface area of the neuron so as
to increase the probability of a molecule encountering its receptor [ 27 ]. Mature
OSNs are identified by the expression of olfactory marker protein (OMP) [ 28 , 29 ]
and are bipolar cells that project their un-myelinated axons through the cribriform