The olfactory mucosa is the neuroepithelial

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

lining the roof and upper parts of the

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

and lateral wall of the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nas ...

which contains bipolar neurons of the primary receptor neurons of the olfactory pathway, as well as supporting cells. The neurons' dendrites project towards the nasal cavity while their axons ascend through the

cribriform plate In mammalian anatomy, the cribriform plate (Latin for lit. '' sieve-shaped''), horizontal lamina or lamina cribrosa is part of the ethmoid bone. It is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities. It s ...

as the olfactory nerves. The part of the nasal cavity that is lined with olfactory mucosa is known as the olfactory region (''pars olfactoria tunicae mucosae nasi''), while the rest of the nasal cavity that is lined by ordinary respiratory mucosa is known as the respiratory region.

Structure

Olfactory mucosa lines about 5cm² of the posterosuperior parts of the lateral nasal wall. Parts of the nasal cavity lined by olfactory mucosa include: parts of the roof of the nasal cavity, the superior nasal concha and some upper parts of the middle nasal concha, parts of the nasal septum, and the sphenoethmoidal recess. The olfactory mucosa is thicker and lighter in colour (yellowish-brown) in comparison to the (pinkish) respiratory mucosa lining the rest of the nasal cavity. Glands of the olfactory mucosa secrete a mostly serous fluid.

Histology

The olfactory mucosa consists of the

olfactory epithelium The olfactory epithelium is a specialized epithelium, epithelial tissue inside the nasal cavity that is involved in olfaction, smell. In humans, it measures and lies on the roof of the nasal cavity about above and behind the nostrils. The olfact ...

and the underlying

lamina propria The lamina propria is a thin layer of connective tissue that forms part of the moist linings known as mucous membranes or mucosae, which line various tubes in the body, such as the respiratory tract, the gastrointestinal tract, and the urogenital ...

, connective tissue containing fibroblasts, blood vessels,

Bowman's glands Olfactory glands, also known as Bowman's glands, are a type of nasal gland situated in the part of the olfactory mucosa beneath the olfactory epithelium, that is the lamina propria, a connective tissue also containing fibroblasts, blood vessels ...

and bundles of fine

axons An axon (from Greek ἄξων ''áxōn'', axis) or nerve fiber (or nerve fibre: see spelling differences) is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action pot ...

from the olfactory

neurons A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

. In

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

, the olfactory epithelium consists of a three basic cell types: bipolar

olfactory receptor neuron An olfactory receptor neuron (ORN), also called an olfactory sensory neuron (OSN), is a sensory neuron within the olfactory system. Structure Humans have between 10 and 20 million olfactory receptor neurons (ORNs). In vertebrates, ORNs are Bi ...

sustentacular cell A sustentacular cell is a type of cell primarily associated with structural support, they can be found in various tissues. * Sustentacular cells of the olfactory epithelium (also called supporting cells or Sertoli cells) have been shown to be inv ...

s, a type of supporting cell; and basal cells, the

stem cell In multicellular organisms, stem cells are undifferentiated or partially differentiated cells that can change into various types of cells and proliferate indefinitely to produce more of the same stem cell. They are the earliest type of cell ...

s that continuously give rise to new olfactory receptor neurons and sustentacular cells.

Electron microscopy An electron microscope is a microscope that uses a beam of electrons as a source of illumination. It uses electron optics that are analogous to the glass lenses of an optical light microscope to control the electron beam, for instance focusing i ...

studies show that Bowman's glands contain cells with large secretory vesicles. The exact composition of the secretions from Bowman's glands is unclear, but there is evidence that they produce odorant binding protein.

Physiology

The

mucus Mucus (, ) is a slippery aqueous secretion produced by, and covering, mucous membranes. It is typically produced from cells found in mucous glands, although it may also originate from mixed glands, which contain both Serous fluid, serous and muc ...

protects the olfactory epithelium and allows

odor An odor (American English) or odour ( Commonwealth English; see spelling differences) is a smell or a scent caused by one or more volatilized chemical compounds generally found in low concentrations that humans and many animals can perceive ...

s to dissolve so that they can be detected by

Research

Adult stem cell harvesting Cells in the olfactory mucosa have been used in clinical trials for

adult stem cell Adult stem cells are undifferentiated cells, found throughout the body after development, that multiply by cell division to replenish dying cells and regenerate damaged tissues. Also known as somatic stem cells (from Greek σωματικóς ...

therapeutic treatments and successfully harvested for future applications. CB1 receptors and obesity Type 1 cannabinoid receptors (CB1 receptors) are present in the sustentacular cells of the olfactory mucosa, in the periglomerular cells of the

olfactory bulb The olfactory bulb (Latin: ''bulbus olfactorius'') is a neural structure of the vertebrate forebrain involved in olfaction, the sense of smell. It sends olfactory information to be further processed in the amygdala, the orbitofrontal cortex (OF ...

, and in the anterior olfactory nucleus and olfactory cortices. A study in 2008 in mice has shown that the level of CB1 expression in various brain regions, including the olfactory nucleus, is modulated by diet-induced

obesity Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...

References

{{Olfactory_system Olfactory system

Structure

Histology

Physiology

Research

See also

References