22.1 Anatomy and normal microbiota of the respiratory tract  (Page 4/12)

Signs and symptoms of respiratory infection

Microbial diseases of the respiratory system typically result in an acute inflammatory response. These infections can be grouped by the location affected and have names ending in “itis”, which literally means inflammation of . For instance, rhinitis is an inflammation of the nasal cavities, often characteristic of the common cold. Rhinitis may also be associated with hay fever allergies or other irritants. Inflammation of the sinuses is called sinusitis inflammation of the ear is called otitis . Otitis media is an inflammation of the middle ear. A variety of microbes can cause pharyngitis , commonly known as a sore throat. An inflammation of the larynx is called laryngitis . The resulting inflammation may interfere with vocal cord function, causing voice loss. When tonsils are inflamed, it is called tonsillitis . Chronic cases of tonsillitis may be treated surgically with tonsillectomy. More rarely, the epiglottis can be infected, a condition called epiglottitis . In the lower respiratory system, the inflammation of the bronchial tubes results in bronchitis . Most serious of all is pneumonia , in which the alveoli in the lungs are infected and become inflamed. Pus and edema accumulate and fill the alveoli with fluids (called consolidations). This reduces the lungs’ ability to exchange gases and often results in a productive cough expelling phlegm and mucus. Cases of pneumonia can range from mild to life-threatening, and remain an important cause of mortality in the very young and very old.

Key concepts and summary

• The respiratory tract is divided into upper and lower regions at the epiglottis .
• Air enters the upper respiratory tract through the nasal cavity and mouth, which both lead to the pharynx . The lower respiratory tract extends from the larynx into the trachea before branching into the bronchi , which divide further to form the bronchioles , which terminate in alveoli , where gas exchange occurs.
• The upper respiratory tract is colonized by an extensive and diverse normal microbiota, many of which are potential pathogens. Few microbial inhabitants have been found in the lower respiratory tract, and these may be transients.
• Members of the normal microbiota may cause opportunistic infections, using a variety of strategies to overcome the innate nonspecific defenses (including the mucociliary escalator) and adaptive specific defenses of the respiratory system.
• Effective vaccines are available for many common respiratory pathogens, both bacterial and viral.
• Most respiratory infections result in inflammation of the infected tissues; these conditions are given names ending in -itis , such as rhinitis , sinusitis , otitis , pharyngitis , and bronchitis .

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