Bronchi Function, Parts and Location
The dichotomous branching of the tracheal tube at the point of sternal angle gives rise to two comparatively smaller tubes, viz. the left and the right bronchi (singular: bronchus). Each of the pair of bronchi extends below the 5th thoracic vertebrae to meet either of the lungs. However, it is not the ultimate division of windpipe; further branching takes place deeper into the lungs with the gradual decrease in the diameter of the bronchial lumen reaching the size of smallest airways, called respiratory sacs. Structurally composed of cartilaginous material, the bronchi show a significant amount of flexibility that substantially contributes to their functioning efficiency. Any abnormal condition in the structure gives rise to great disturbance and severe symptoms of the respiratory system, but a number of remedial strategies are available for almost all of such disorders.
Parts of Bronchi
The mainstem bronchi are two in number each penetrating into bilaterally symmetrical sides of the human body. However, you can easily witness certain differences in the structure of the left and right bronchi. For example, the right main bronchus is more vertical, wider and shorter in length than the left main bronchus. As a consequence of the further division of the left mainstem bronchus, two lobar bronchi are formed while right major bronchus gives rise to three lobar bronchi. The segmentalinic or tertiary bronchial tubes are formed by the subdivision of lobar bronchi, and are separated from one another by a septum made up of connective tissue. They are usually 10 in number in each of the lung lobes, but they may also fuse with one another due to the developmental processes in the region. Smooth muscles are always present along the D-shaped incomplete rings of the bronchial tubes which are, in turn, composed of hyaline cartilage.
Functions of Bronchi
Though their walls do not let the respiratory gases pass across them, the bronchial canals are the main channels for the passage of airstream towards the major respiratory organs. They also make significant contribution to the protection of lungs against germs and dirt particles which are trapped in the mucous lining of the lumen and are expelled upward and removed out of the windpipe with the help of ciliated cells. The hyaline cartilaginous material that forms the D-shaped incomplete rings of the bronchial walls prevents the tubes from collapsing and obstructing the flow of air. However, with the passage of time as you grow older, this soft flexible material is converted into hard and rigid bony substance, thus reducing the overall efficiency of the structure. The alveolar sacs (or alveoli) are formed as a result of many subdivisions of the mainstem bronchi and these are the places where the exchange of respiratory gases takes place.
Diseases of Bronchi
There are a number of respiratory disorders that are primarily associated with the subdivisions of windpipe, i.e. bronchi, bronchioles and alveoli or respiratory sacs. For example, bronchitis-as the very name suggests-is the inflammatory disorder of bronchi which may occur in either of the two major forms, viz. chronic and acute one. Chronic bronchitis results from the prolonged exposure to the irritants and smoking habits, while acute form is the result of the bacterial and viral infections. As a response to the allergens (antigens producing abnormally vigorous immune response), hyperactivity is generated in the bronchial canals, a condition known as asthma. Because of its vertical position, the right main bronchus is more vulnerable to the disorders as germs and dust particles present in the atmospheric air get entry into the right lung quite easily, and cause mild or severe medical conditions.