he nasal passage is part of the conducting zones of the respiratory system. The nose being a conducting zone of the respiratory system has a number of functions. One of the functions is that it traps dust particles from the inhaled air as it passes through the nasal cavity (Drake et al., 2015) . This function is important because dust particles lodging into the lungs would clog the airways and also increase the likelihood of infections. In order to carry out this function effectively, the inside of the nose is lined with hairs that help to trap the dust particles.
The nose is also responsible for moistening the air passing through it. This is important so that the air does not harm/damage the delicate structures found within the lung (Drake et al., 2015) . In order to carry out this function effectively, the nose is equipped with glands whose secretions keep the epithelium of the nasal cavity warm. As the air passes through the nasal cavity, the epithelium helps to moisten the air before it flows to the lungs.
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The other function of the nasal cavity is to warm the air as it passes through on its way to the lungs. It is important to warm the air so that it does not destroy the delicate structures of the lungs (Drake et al., 2015) . The nose is equipped with a rich network of capillaries just beneath the epithelium. The heat from the blood flowing through these capillaries helps to warm the air. The nasal cavity has extensions of mucosa called the turbinates. These extensions of the mucosa increase the surface area of the nasal cavity and as a result, there is a large surface over which the air can be moistened, filtered and warmed before it flows to the lungs. Another adaptation of the nose is the fact that it has an olfactory mucosa which helps to smell the inhaled air in order to determine whether it is fit for inhalation or not.
Question 2
The pharynx is divided into 3 anatomical regions. These 3 sections are namely; the nasopharynx, the oropharynx and the hypopharynx (Drake et al., 2015) . Each region of the pharynx has a unique epithelium that is specialized to fit the role of each section. The nasopharynx is lined up with ciliated columnar epithelium. This type of epithelium is important in this part of the pharynx as it continues with the work of the nasal cavity of warming, filtering and humidifying the air. The oropharynx which is the pharynx proper is lined up with stratified squamous epithelium which is thicker than the rest of the pharynx so that it cannot suffer damage as food is being swallowed past it. On the other hand, the hypopharynx is lined up with non -keratinized stratified squamous epithelium.
The nasopharynx is the uppermost part of the pharynx. This section of the pharynx runs from the base of the skull all the way down to the upper surface of the soft palate (Drake et al., 2015) . This part of the pharynx acts as the transition zone between the nasal cavity and the pharynx. As stated above, it is lined up with ciliated columnar epithelium that has numerous goblet cells. This type of epithelium enables this part of the pharynx to continue with the work of cleaning the air, humidifying it as well as moistening it before it flows to the lungs for gaseous exchange.
The nasopharynx has a number of important structures in the body. At the roof of the pharynx is the adenoid glands. These glands have an important role to play in the immune system but sometimes they get hypertrophied causing obstruction of air flow and have to be removed as they cause a number of problems such as obstructive sleep apnea (Drake et al., 2015) . When hypertrophied, they also greatly affect the development of the affected children. The Eustachian tube also opens at the level of the nasopharynx.
References
Drake, R. L., Mitchell, A. W., & Vogl, W. (2015). Gray's anatomy for students .
