As a thin layer of tissue, the nasal mucosa lines the entire nasal cavity without the nasal vestibule. It provides the first defense against bacteria, viruses or fungi entering the body. Inflammation of the nasal mucosa manifests as a cold (rhinitis).
What is the nasal mucosa?
The nasal mucosa is a thin mucus-forming layer of tissue that lines almost the entire nasal cavity. The nasal vestibule is an exception. Instead of nasal mucosa, it is equipped with keratinized squamous epithelium. The nasal mucosa is divided into two regions. These are the regio olfactoria and the regio respiratoria. The regio olfactoria represents the olfactory mucosa and is located at the upper nasal entrance (meatus nasi superior). It has special olfactory cells that serve to perceive odors. Otherwise, the regio respiratoria occupies almost the entire nasal cavity. It is equipped with a respiratory ciliated epithelium. The nasal mucosa is regenerated as part of the so-called nasal cycle. The nasal cycle represents the periodic swelling of the turbinates without the need for an external stimulus. It is controlled by the hypothalamus. With the help of the nasal cycle, the nasal mucosa retains moisture while humidifying the air we breathe.
Anatomy and structure
The nasal mucosa consists of three tissue layers. This is true for both the respiratory nasal mucosa and the olfactory mucosa. Thus, the respiratory nasal mucosa consists of the lamina propia, the basement membrane, and a multilayered ciliated epithelium with goblet cells. The lamina propia represents a thin layer of connective tissue located beneath the basement membrane. It contains a dense network of blood capillaries. These are connected to a superficial venous plexus. The venous plexus regulates the change in volume of the corpus cavernosum and thus influences the modification of air circulation. The basement membrane, in turn, is composed of epithelial cells, which form the basis for the respiratory nasal mucosa. The ciliated and goblet cells are formed from the basal cells. They are the only cells that reach the free surface. The basal cells are located in the basement membrane and are the stem cells for the regeneration of the ciliated and goblet cells. As glandular cells, the goblet cells are responsible for the production of nasal secretions. The olfactory mucosa in the upper nasal passage also consists of three tissue layers. Of these, two layers are similar in structure to the respiratory nasal mucosa. These are also the lamina propia and the basement membrane. Above the basement membrane, however, lies a specialized olfactory epithelium. It consists of supporting cells and olfactory cells. The olfactory cells are neurons whose axons float in the mucus layer. Below the supporting cells are the basal cells, which act as the stem cells of the olfactory cells. The olfactory cells have a life span of 60 days and are constantly renewed from the stem cell reservoir.
Function and tasks
The main function of the nasal mucosa is to defend against infection. This task is performed by the respiratory nasal mucosa. First, pathogens are secreted through the mucus, which can then be removed by the constant flicker. The nasal mucus consists of two layers. This is a thin fluid sol layer, which lies under a discontinuous gel layer. The gel layer is transported by the cilia, which beat within the sol layer. At a PH of 7.5 to 7.6, the sol is transferred to the gel. The most important components of the nasal mucus are the mucins. They give the mucus its viscoelastic properties and are responsible for the immune response to various infections and interaction with the existing microflora. The olfactory mucosa, in turn, has the task of absorbing odors and transmitting them to the brain for processing. There, the olfactory information is released for perception.
Diseases
Diseases of the nasal mucosa manifest themselves either with increased mucus production or with drying of the nose. Often, these signs of illness represent only symptoms of underlying diseases. There are many causes of increased mucus production. It is rhinitis, which is also colloquially referred to as the common cold. Often there is an infection with viruses. Of course, there are also allergy-related forms of rhinitis.The best-known example is the so-called hay fever, which occurs particularly in spring during the pollen count. But other allergens also frequently trigger increased mucus formation in the nose. Sometimes a cold is triggered by harmless influences in the context of nasal hyperreactivity. Nasal hyperreactivity refers to a hypersensitive nose. It is caused by malfunctions of hormones, messenger substances and proteins. Chronic inflammation of the nasal mucosa can lead to polyps. Polyps are benign growths in the nasal mucosa. However, they obstruct nasal breathing and in the process fire further inflammatory processes. Therefore, nasal polyps should be surgically removed. The causes of chronic inflammation can be infections with viruses, bacteria or fungi. Allergic processes also play a role. Another problem of the nasal mucosa is its complete dehydration. An incipient cold often manifests itself in a dry nose. In this case, however, it is only a temporary problem. When dry nose becomes a chronic condition, it can have serious health consequences. Often, dry indoor air or extreme dust exposure play a role in chronicity. Dry nose manifests itself in obstructed nasal breathing, a feeling of dryness in the nose, deterioration of the ability to smell or nosebleeds. Crusts and scabs form. Without treatment, the nose may lose its function completely. As a result, the susceptibility to infections increases. In rare cases, bacteria settle in the dry mucosa, leading to unpleasant odors from the nose.
Typical and common nasal diseases
- Stuffy nose
- Nasal polyps
- Sinusitis