Bronchi

Updated on

Eva Rudolf-Müller is a freelance writer in the medical team. She studied human medicine and newspaper sciences and has repeatedly worked in both areas - as a doctor in the clinic, as a reviewer, and as a medical journalist for various specialist journals. She is currently working in online journalism, where a wide range of medicine is offered to everyone.

More about the experts All content is checked by medical journalists.

The bronchi are part of the tube system of the lungs that serves as a control system for the air you breathe. After dividing the windpipe (trachea) into a right and a left main bronchus (one branch each for the two lungs), numerous other branches take place, which fill the entire lungs and finally open into the alveoli, where the gas exchange between breathing air and Blood occurs. Read everything you need to know about the bronchi here!

What are the bronchi

The bronchi form a richly branched system of tubes in the lungs - a control system for the air you breathe: the two main bronchi emerge from the division of the windpipe (trachea) and each lead into one of the two lungs. Numerous other branches take place there, with the bronchi becoming smaller and thinner-walled: First, each main bronchus divides into three (right lung) or two (left lung) lobes - corresponding to the three or two lung lobes. The fact that the left lung has one less lobe than the right is because the heart needs space.

The lobe bronchi branch further into the segment bronchi, which also branch out further. The smallest bronchi, less than a millimeter in diameter, are called bronchioles. They open into the tiny, delicate alveoli, in which the gas exchange takes place.

With increasing branching of the bronchi, their wall structure changes: First, the walls are reinforced with cartilage braces to keep them stable. The free ends of these cartilage braces are braced by strands of smooth muscles that are controlled by the nervous system. In the course of branching, the amount of cartilage in the walls decreases, while the amount of smooth muscles increases. Finally, the bronchioles only have a muscle wall without cartilage.

What is the function of the bronchi?

The bronchi carry the air from the upper respiratory tract (nose, mouth, throat, larynx) and the windpipe (trachea) to the approximately 300 million pulmonary sacs (alveoli) at the end of the bronchioles. These are surrounded by a network of tiny blood vessels (capillaries) and are the place for gas exchange: Oxygen from the breath is released into the blood through the wafer-thin walls of the alveoli and carbon dioxide from the blood is absorbed into the breath, which is then exhaled.

The interior of the bronchi (like that of the trachea and upper airways) is lined by a respiratory epithelium. Among other things, it contains cells that produce mucus to which small and tiny particles that have entered with the air you breathe adhere. Neighboring ciliated epithelial cells then transport these particles with their cilia to the outside, where they can be coughed up.

In physically active phases, for example during sport or during hard physical work, the activation of the sympathetic nervous system relaxes the muscles around the bronchi. As a result, these have a larger diameter and more air can flow through and reach the alveoli: the blood is supplied with more oxygen. In contrast, when the body is resting, the bronchi narrow because the parasympathetic nervous system is then activated.

Where are the bronchi located?

The bronchi are located inside the lungs in the chest. The main bronchi begin at the end of the windpipe at the level of the fourth thoracic vertebra.

What problems can the bronchi cause?

The most common bronchial health problem is acute inflammation (bronchitis). It is usually caused by viruses and usually heals without complications, but it can also become chronic. If the bronchitis caused by the virus causes additional colonization of the mucous membrane by bacteria, treatment with antibiotics is necessary.

In people with bronchial asthma, allergens (allergy triggers) or irritants (such as cold air or smoke) cause the bronchi to contract like a spasm, which affects breathing like a fit (asthma attack). Experts estimate that around 100 million people worldwide suffer from asthma.

Chronic narrowing and inflammation of the bronchi is also possible (especially in long-term smokers). Then one speaks of chronic obstructive bronchitis. If the alveoli are also partially destroyed and overstretched (pulmonary emphysema), you have chronic obstructive pulmonary disease (COPD).

Smoking can also trigger the formation of a malignant tumor on the bronchi. This bronchial carcinoma (lung cancer) is the most common cause of cancer-related death in men and the third most common cause of death in women.

Tags:  Menstruation pregnancy desire to have children