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The Secret of Smell: Why Do We Smell Thousands of Odors?
Smells are ubiquitous in our daily lives and have a profound impact on our emotions, memories and choices. The power of smell seems beyond words, so how exactly do we smell these things? It all has to do with the brain's olfactory system and its structure.
The olfactory epithelium is a special epithelial tissue located in the nasal cavity. This network of cells can not only sense odors, but also has amazing regenerative abilities.
Structure of the olfactory epithelium
In humans, the olfactory epithelium covers an area of about 5 square centimeters and is located at the top of the nasal cavity, about 7 centimeters high. This area is specifically responsible for detecting odor molecules in the air. The olfactory epithelium is made up of four different cell types:
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Olfactory sensory neurons
- Supporting cells
- Basal cells
- Brush cells
Olfactory sensory neurons are specialized sensory neurons that interact with odor molecules through their non-motile cilia that extend into the air. The dendrites of these sensory neurons have many olfactory receptors that are responsible for capturing odors from the air.
The existence of olfactory receptors allows us to identify thousands of different smells, which is one of the mysteries of olfactory perception.
Supporting cells and basal cells
Supporting cells are similar to glial cells and are located in the uppermost layer of the olfactory epithelium. These cells not only provide metabolic and physical support, but also work with basal cells to maintain the integrity and function of the epithelium. Basal cells are stem cells that can divide and differentiate into other cell types, and their main function is to renew the olfactory epithelium when necessary.
Brush Cells
Brush cells have microvilli that contact the afferent nerve endings of the trigeminal nerve and are specialized for transmitting general sensations.
Importance in development
The olfactory epithelium develops from two structures: the nasal plate and neural crest cells. At early embryonic stages, there are relatively few cell types in the olfactory epithelium, primarily upper and basal progenitor cells and immature olfactory sensory neurons. As development progresses, neurons gradually differentiate and express olfactory receptors.
Clinical significanceThe olfactory epithelium can be damaged by toxic fumes in the environment, physical injury within the nasal cavity, or the use of certain nasal sprays. Despite its ability to regenerate, in extreme cases the damage can be permanent, leading to loss of smell.
A deeper understanding of the olfactory system is not only important for scientific research, but also for the treatment of individuals whose quality of life is affected by impaired sense of smell.
But returning to our ability to smell, isn’t the diversity of scents and their impact on our lives a deeper connection?
