The bronchiole refers to the first airway canals with no cartilage. They are part of the bronchi. The end part of these structures is at the point where they enter the circular sacs known as the alveoli.

The part of the lung that is directly ventilated by the bronchioles is called pulmonary lobule. These structures have a wall thickness of about less than 1 mm. The internal lining of the structures is composed of ciliated cuboidal epithelium and also a lining of smooth muscles.


The structures further subdivide into smaller terminal branches of less than 0.5 mm thickness.

The terminal structures in turn are subdivided into respiratory bronchioles and eventually subdivided again into alveolar ducts.

The terminal structures are the final stage of the structures conducting air in the respiratory system. The actual gas exchange begins at respiratory bronchiole region.

The diameter of the structures is highly crucial when it comes to identifying the airflow. The size of diameter can either increase or decrease airflow into the system.

Increased diameter of the bronchiole system is called brochodilation and can be activated by sympathetic nerves or epinephrine. Decreased diameter is called bronchoconstriction and can be stimulated by parasympathetic nerves, histamine, chemical irritants and cold air jus to mention a few causatives.

The bronchioles are not free of infections. The most common condition is the bronchitis and it affects the inner lining of the structures making the organ to become inflamed.

The inflammation constricts the bronchioles thereby preventing secreted mucous from getting eliminated from the body.

Bronchiole infection classifications

The main categories of the condition include chronic and the acute condition. The acute infection is the most common and mainly occurs after an individual has been infected by the common cold as well as any other respiratory system infection.

Generally, this condition heals alone after a number of days although it lingers some people for up to three weeks characterized by intensified coughing.

The chronic bronchiole infection is a severe condition where the bronchioles are continuously inflamed. This infection is common among smokers and calls for medical attention. It is classified among chronic pulmonary diseases (COPD).

Causes of bronchioles infection

The acute bronchiole infection is caused by the virus that is also behind common cold. However, exposure to polluted air can cause allergic reaction from the pollutants that can result into the condition. The main pollutants that can cause this include passive smoking, smog and exhaust fumes among others.

The chronic bronchioles infection mainly comes from excessive use of tobacco as well as long term exposure to the polluted air. People living in areas close to the industrial plants are exposed to a lot of irritants and toxic fumes that can cause the infection.


Common signs of acute bronchiole infection include spitting phlegm, coughing, wheezing, labored breathing, chills, fever, fatigue and pain in the lungs. Cough that can last for a number of weeks is however the main symptom of the condition.

The chronic condition causes bronchiole to become scarred as a result of persistent inflammation. The inflammation results in thickened airways and tube lining. The main symptom of the condition is cough that can be escalated by the damp and cold weather common in the morning.