Describe how air is modified by the nasal passages, and describe the special structures that allow this modification
The nasal passages play a crucial role in modifying the air we breathe before it reaches our lungs. They are lined with a specialized tissue called the respiratory epithelium, which is covered in tiny hair-like structures called cilia. These cilia are constantly moving in a wave-like motion, helping to filter and warm the incoming air.
The most noticeable modification that occurs in the nasal passages is air filtration. As we breathe in, the nasal hairs lining the nasal passages, called vibrissae, trap large particles like dust, pollen, and dirt. This prevents these particles from entering the lungs and potentially causing respiratory issues.
Another modification is the warming and humidification of the air. The nasal passages are richly supplied with blood vessels, which help to warm the cool air as it enters the nose. This is important because cold air can irritate the delicate tissues of the respiratory system. Additionally, the respiratory epithelium produces mucus, which helps to humidify the air by adding moisture to it. The moist air is more comfortable to breathe and also helps to prevent drying out of the lung tissues.
The nasal passages also participate in the sense of smell. The roof of the nasal cavity contains olfactory epithelium, which consists of specialized cells called olfactory receptors. These receptors detect different odors in the air and send signals to the brain, allowing us to perceive and distinguish various smells.
In summary, the modifications that occur in the nasal passages include air filtration by the vibrissae, warming and humidification of the air through the rich blood supply and production of mucus, and participation in the sense of smell through the olfactory receptor cells.