The clinical expression of allergy in the lungs

• Published in: Allergy (Copenhagen) 1999-01, Vol.54 (1), p.7-14
• Main Authors: O'Byrne, P.M., Inman, M.D.
• Format: Article
• Language: English
• Subjects: aerobiology; Allergic diseases; asthma; Asthma - physiopathology; Biological and medical sciences; Bronchial Hyperreactivity; cross-reactivity; Humans; Immunopathology; Medical sciences; Respiratory and ent allergic diseases; Respiratory Hypersensitivity - physiopathology; rhinitis; seasonal allergy; Zygophyllum fabago pollen
• ISSN: 0105-4538; 1398-9995
• DOI: 10.1111/all.1999.54.1.7

The main function of the lungs is gas exchange. This is achieved by moving inspired air down a dichotomous series of branching airways to the gas-exchange portions of the lungs, the alveoli. The average tidal volume for an adult at rest is 500 ml and the respiratory rate is 12/min, giving an average minute ventilation at rest of 6 l/min. This means that, on average, more than 8500 l of air is inspired each day by an adult at rest. However, during exercise, the minute ventilation can exceed 120 l/min. The inspired air reaching the alveoli must be fully humidified at a temperature of 37 degree C, sterile, and free of noxious agents. The responsibility for conditioning the inspired air falls on the extra- and intrathoracic airways. The intrathoracic airways begin with the trachea, which divides into the right and left main-stem bronchi. The latter subsequently divide into bronchi supplying the upper and lower lobes of the left lung and the upper, middle, and lower lobes of the right lung. After approximately 25 more divisions, the bronchi become bronchioles, which then become respiratory bronchioles and then alveolar ducts, leading to the alveoli. Bronchi all contain cartilage and airway smooth muscle, while bronchioles lack cartilage, and alveolar ducts do not have smooth muscle.