Respiratory Tract Infection: Causes, Symptoms, and Treatment

The respiration process begins at the nose. Air enters through the nares (nostril openings). The nares allow air to enter into the nasal cavity that is separated into right and left portions by the nasal septum . The anterior part of the nasal septum is made up of the septal cartilage while the posterior is formed by the ethmoid bone and thin vomer bones (BC Campus, 2019 p.146). Every lateral wall of the nasal cavity comprises of three bony structures namely; superior , middle and inferior nasal conchae . The physiology of the nose comprises of several structures designed to warm up air and trap dust particles. The nares as well as the anterior section of the nasal cavities comprise of mucous membranes that have hair follicles and sebaceous glands which obstruct the passage of large particles into the nasal cavity. On the other hand, other important structures such as meatuses , conchae and paranasal sinuses have respiratory epithelium which secretes mucus that traps dust particles. 

The exterior part of the nasal cavity leads to the pharynx , which is made up of three major regions; the nasopharynx , oropharynx , and laryngopharynx , in that order. The pharynx contains ciliated epithelium , which traps dust particles just like the one in the nasal cavity. Subsequently, the pharynx connects to the larynx whose anterior is made of the thyroid cartilage , superior made of epiglottis and the inferior portion made up of cricoid cartilage (BC Campus, 2019 p.146). The larynx forms the link between the pharynx and the trachea and helps to regulate the amount of air entering and leaving the lungs. The larynx leads to the trachea , which comprises of C-shaped cartilages . The trachea, as well as the primary bronchi , acts as passageways for air into the lungs. The lungs comprise of the alveoli (air sacs), which allow oxygen to be absorbed by the blood and carbon dioxide to be released out. This process causes lungs to expand and contract once air is inhaled and exhaled. At the base of the lungs is the diaphragm , which expands and contracts, as well as separates the chest cavity from the abdominal cavity . 

Reference  

BC Campus. (2019). Anatomy and Physiology . https://opentextbc.ca/anatomyandphysiology/front-matter/preface-2/