Bronchi - Anatomy and Functions

Introduction

The human body has a different system to regulate body functions. For example, the human respiratory system has important work in functioning the inhalation of oxygen and exhalation of carbon dioxide. Bronchi are part of the respiratory system, which works to carry air to the lungs. Bronchi is a plural form of the word bronchus. This topic describes the bronchi, their parts, anatomy, functions, and conditions that are associated with bronchi.

What Is Bronchi?

Bronchi are the air tubes that carry air from the trachea (windpipe) to the lungs. Bronchi is the plural form of the word bronchus. They have two main air tubes, the right and left bronchus, which go into the right and left lungs. And further divides into small bronchi inside the lung, forming a tree branch. In addition, these bronchi have a secondary to tertiary to further segmental bronchitis that leads to small bronchi called bronchioles. These bronchi carry oxygen and carbon dioxide, which get exchanged at the alveoli present in the lungs.

What Are the Different Parts of Bronchi?

The bronchi look like a tree, as the main bronchus resembles the trunk of the tree, and the subdivision, as the branches of the tree. The two main branches are the right and the left bronchus.

• The right bronchus further divides into three subdivisions.
• The left bronchus further subdivides into two subdivisions.

What Are the Subdivisions of Bronchus?

• Lobar bronchi, which is the second division of the bronchus, involves the section of the lobe (section of the lungs).
• Segmental bronchi involve a segment of an individual lobe and a tertiary division of the bronchus.
• The terminal bronchioles are a subdivision of segmental bronchi and, thus, the smallest segment of bronchi.

What Is the Anatomy of the Bronchi?

• The trachea divides into the bronchi at the level of the thoracic vertebrae (middle part of the spine).
• There is a point where the trachea divides into bronchi called the carina. They further divide into the right and left bronchi.
• The right bronchus is wider and shorter than the left bronchus.
• The right bronchus goes to the right lung at the level of the fifth thoracic vertebrae and then divides into three subdivisions called lobar bronchi. The right bronchus has an azygos vein arch (blood vessels that carry blood from the chest and the stomach region to the heart) from behind and a right pulmonary artery (a blood vessel that transports impure blood from the heart’s right side to the lungs for purification or oxygenation) from below it.
• The left bronchus is smaller and longer than the right bronchus. The left main bronchus enters the left lung at the sixth thoracic vertebrae and then passes the aortic arch (a division of the heart’s main blood vessel that supplies blood to the upper extremities) (below), esophagus (windpipe) (front), thoracic duct (the largest lymphatic vessel), and the descending aorta (aorta’s longest part).
• The left bronchus further divides into two secondary lobar divisions. And on further division, these secondary divisions form a tertiary division that supplies the bronchopulmonary segment (lungs, certain parts supplied by segmental bronchus and their vessels).
• The human body has ten bronchopulmonary segments in the left lung and eight in the right lung. So accordingly, the bronchi also subdivide differently in the two lungs.
• The terminal bronchioles also have respiratory bronchioles, which involve 2 to 11 alveolar ducts. These alveolar ducts contain nearly five to six alveolar sacs. These alveolar sacs have an alveolus which is the basic anatomic unit of the gas exchanges.

What Is the Histology of the Bronchi?

• The histology of bronchi contains hyaline cartilage (bluish-white cartilage evident in the joints, respiratory tract, etc) rings and a lining of smooth muscles all around.
• The lining of smooth muscles increases on the decrease in the hyaline lining.
• The lining of the bronchi goes through a transition as the cells from ciliated pseudostratified columnar epithelium (a form of respiratory lining predominant in the respiratory tract and trachea) move to the simple cuboidal epithelium (one form of epithelial cell that contains cube-like cells that comprises large, round, and nuclei present in the center) and, lastly, to simple squamous epithelium (another form of epithelium that forms the lining of the blood vessels and other body cavities).

What Is the Function of the Bronchi?

The function of bronchi are:

• They carry the air to and from the lungs.
• They moisten the air for easy breathing.
• They clear out the foreign particles.
• The airways have cells that can secrete mucus.
• They protect the lungs from infection by trapping bacteria, fungi, and other particles going into the lungs.
• These bronchi have cilia over their cells that move the mucus and help them clear out the particles through cough from the body.

What Are the Conditions Associated With the Bronchi?

Some of the associated conditions that are related to bronchi are:

• Asthma: Asthma is a lung condition in which the airways get narrowed and swollen due to difficulty breathing. Asthma conditions inflame these bronchi.
• Bronchiectasis: It is also a lung condition in which the bronchi have been damaged with an abnormal widening. It also causes excessive mucus formation.
• Bronchitis: It is the inflammation of the bronchi that can lead to irritation. This condition gives rise to the production of yellowish-gray mucus (phlegm).
• Bronchiolitis: It is a lung infection that involves the bronchioles.
• Chronic Obstructive Pulmonary Disease (COPD): It is a chronic inflammatory lung disease that causes obstruction in the airflow. It includes emphysema (a lung condition that leads to breathing difficulty) and bronchitis. It has shown symptoms like shortness of breath, wheezing, cough, and mucus production.
• Bronchopulmonary Dysplasia: When the lungs of the baby are not fully developed, it causes a breathing problem called bronchopulmonary dysplasia. It usually occurs in premature babies who require oxygen therapy.
• Bronchogenic Carcinoma: Bronchogenic carcinoma are cancers that originate from the bronchi or the bronchioles. These are the types of lung cancers that are now called non-small cell lung cancer and small cell lung cancer. These can be aggressive also.
• Bronchopleural Fistula: It is an abnormal tract that has developed in between the bronchi and spaces that lines the lungs.

How Is an Abnormality in the Bronchi Diagnosed?

Diagnoses of the bronchi are performed by:

• Bronchoscopy: It is performed by using a flexible tube and camera that can go inside the bronchi.
• CT (Computed Tomography) Scans: It is an X-ray image of the lungs using a computer in which the lungs can be visible from different angles.
• Spirometry: It is the method to measure the air exhaled forcefully, which checks the lungs.
• Endobronchial Ultrasound: It is also a type of bronchoscopy to detect various forms of lung disorders.

What Is the Treatment of the Conditions Related to Bronchi?

There are different treatment methods. Some of them are:

• Corticosteroids.
• Bronchodilators.
• Oxygen supply.
• Airway clearance devices.
• Chest physical therapy.
• Cancer treatment.

Conclusion

Bronchi are parts of the respiratory system, and they carry the air inhaled from the windpipe to the lungs. They have an important role in supplying oxygen to the lungs by subdividing them into secondary and tertiary bronchi. Bronchi are associated with asthma, bronchitis, bronchiolitis, bronchopulmonary dysphagia, bronchogenic cancers, and COPD. However, with appropriate diagnosis and treatment, the conditions associated with bronchi are treated appropriately.