Anatomy & Organs

Olfactory mucosa – structure, function & diseases

Olfactory mucosa

The olfactory mucosa is responsible for the sense of smell. It is part of the nasal mucosa in the area of ​​the nasal roof . Diseases of the olfactory mucosa can lead to olfactory disorders.

What is the olfactory mucosa?

The olfactory mucosa contains special sensory cells that absorb smells and transmit the information via electrical impulses to the brain for processing. Inside the olfactory cells, so-called chemoreceptors ensure the absorption of odor molecules.

In humans, the olfactory cells are located in the olfactory region of the nasal mucosa. The olfactory region describes the part of the nasal mucosa that is responsible for the perception of smells. It is located on the left and right roof of the upper nasal cavity. In addition to the olfactory cells, there are also supporting and basal cells in this area. The olfactory cells are so-called bipolar neurons with dendrites and axons as nerve processes .

Dendrites provide the input of electrical impulses, while the axons transmit these impulses. The sensory cells renew themselves every 60 days. The olfactory cells are therefore among the few nerve cells that are constantly renewed. They develop from the basal cells, i.e. from the stem cells of the nasal mucosa. The supporting cells stabilize the tissue statics of the olfactory mucosa.

Anatomy & Structure

The olfactory mucosa located in the roof of the upper nasal mucosa is brown in color and occupies an approximate area of ​​2 x 5 cm. It is composed of olfactory cells, supporting cells, microvilli cells and basal cells. It also contains serous glands .Humans have about 10 – 30 million olfactory sensory cells. In comparison, their number in dogs is around 250 million. Each olfactory cell still has 5 – 20 hairs with olfactory receptors. These hairs protrude from the mucous membrane and are covered with a thin layer of mucus. Odor molecules arriving there dock onto the olfactory receptors and arouse them. There are around 350 different types of olfactory receptors.

Each species only responds to a specific molecule. In this way, 350 different smells can be distinguished. But the processing and filtering of these impressions is accomplished by the bundled outgoing nerve fibers, the axons. These bundles of axons are connected to an upstream part of the brain, the olfactory bulb. This is where the synaptic connection of the sense of smell takes place.

From there, the information is then forwarded to the appropriate brain centers. At the olfactory bulb, the axon cords are divided into two parts. The medial cord reaches the olfactory tubercle . The information is stored there, but remains unconscious. The lateral strand leads to the primary olfactory cortex, where the information from the olfactory mucosa is consciously processed.

Function & Tasks

The olfactory mucosa contributes significantly to the health of the body by performing its function. Because the olfactory function protects the organism and especially the respiratory organs from the harmful effects of toxic substances. Foul-smelling gases create a feeling of disgust, so that the organism in question removes itself from the danger zone as quickly as possible. On the other hand, pleasant smells attract because they are usually associated with positive associations, such as delicious food.

However, the sense of smell is often not taken seriously. However, people who no longer have a sense of smell can enter dangerous situations unnoticed. It is no longer possible for these patients to detect spoiled food or gas escaping from the smell alone.

This is why the corresponding olfactory receptors for vital smells have developed during evolution. Olfactory receptors are specific proteins that are still coupled to a G protein. Using the lock and key principle, they have developed forms that are precisely tailored to certain odor molecules. The signaling molecule is guided to the receptor via a tiny hair in the olfactory cell and connects to it if there is an exact match.

The resulting excitation is then transmitted via the axons. So-called mitral cells in the olfactory bulb probe and then amplify the same smells from the selection of 350 different receptors and forward them to the appropriate brain centers. There, the excitations that certain signaling molecules in the receptor molecules of the olfactory cells have caused are made conscious through smell impressions.

Diseases

Diseases of the nasal mucosa and especially the olfactory mucosa can lead to olfactory disorders. The olfactory disorder is the collective term for a large number of deviating olfactory sensations. First, a distinction must be made between quantitative and qualitative olfactory disorders.Quantitative olfactory disorders indicate a partial (hyposmia) or complete loss (anosmia) of the ability to smell. Hypersensitivity to olfactory stimuli (hyperosmia) also occurs. Causes of anosmia or hyperosmia can be brain diseases , viral infections, chronic inflammation of the nasal mucosa, allergies or side effects of medication. Since the sense of smell is closely linked to the sense of taste, the taste of food can no longer be properly perceived.

This often leads to malnutrition . In addition, there is a risk of food poisoning from spoiled food, especially for older people. Psychological problems, such as depression , can also result from the lack of the sense of smell. Qualitative olfactory disorders are expressed in deviating olfactory sensations. Parosmia results in an altered perception of smells.

A phantosmia allows smells to be perceived that do not exist at all. It can be viewed as an olfactory hallucination . With cacosmia, pleasant odors are perceived as unpleasant, while with euosmia, unpleasant odors appear pleasant. In addition to many other causes, qualitative olfactory disorders can also be caused by damage to the olfactory mucosa.

Typical & common nose diseases

Website | + posts

Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.