The peripheral part of the olfactory apparatus or organ of smell
(Organon olfactus) is that part of the nasal mucous membrane which was
referred to in the description of the nasal cavity as the olfactory
region; this (Regio olfactoria) is limited to the ethmoturbinals and the
adjacent part of the superior turbinal and the septum nasi, in which the
fibers of the olfactory nerve ramify. It is distinguished by its
yellow-brown color, thickness, and softness. It contains characteristic
tubular =olfactory glands= (of Bowman), which are lined by a single
layer of pigmented cells, and a neuro-epithelium, the =olfactory cells=,
the central processes of which extend as non-medullated fibers to the
olfactory bulb.
The epithelium is non-ciliated and is covered by a structureless
limiting layer. It consists essentially of three kinds of cells,
supporting, basal, and olfactory. The supporting cells are of long
columnar form above and contain pigment granules; below they taper and
often branch, and their central processes unite with those of adjacent
cells to form a protoplasmic network. The basal cells are branched and
lie on a basement membrane. The olfactory cells are situated between
the supporting cells; they have the form of long narrow rods, with an
enlarged lower part which is occupied by the nucleus. The peripheral
end pierces the limiting membrane and bears a tuft of fine hair-like
cilia (olfactory hairs). A central process extends from the nucleated
pole of the cell to the olfactory bulb as a non-medullated olfactory
nerve-fiber.
The =vomero-nasal organ= (of Jacobson) lies along each side of the
anterior part of the lower border of the septum nasi. It communicates
with the nasal cavity through the naso-palatine canal. It consists of a
tube of hyaline cartilage lined with mucous membrane; a small part of
the latter along the inner side is olfactory in character.