What causes bronchitis?

Bronchitis is a common disease. The causes of bronchitis may include reduced local respiratory immune function or autonomic nervous system dysfunction. At the same time, external infection cannot be ignored.

1. Reduced local respiratory defense and immune function

The inhaled air first passes through the nasal cavity, which filters, warms and moisturizes the passing air. The nasal hair in particular plays an important role. Therefore, frequent nose picking can easily destroy the first line of defense system and provide an opportunity for large particles to enter the body.

The epithelial cells of the trachea and bronchial mucosa are covered with cilia, which can secrete a large amount of mucus, so they can absorb particles with smaller diameters. At the same time, the cilia constantly swing upward to push the mucus containing foreign matter into the throat, and finally cough it out of the body. This is the annoying phlegm.

Secretory immunoglobulin A (SIgA) is also present in the bronchioles and alveoli, which can directly wrap bacteria and viruses, thus having antiviral and antibacterial effects. Under the action of the above mechanisms, under normal circumstances, the lower respiratory tract (below the larynx) always remains sterile.

When the systemic or local respiratory defense and immune functions are weakened, it provides the internal conditions for the onset of chronic bronchitis. The elderly often have a higher incidence of disease due to decreased respiratory immune function, reduced immunoglobulins, and deterioration of respiratory defense function.

2. Autonomic dysfunction

The human body's autonomic nervous system consists of two opposing and unified parts - the sympathetic nerves and the parasympathetic nerves (vagus nerves). The two are in a state of dynamic balance, which keeps our body in a relatively comfortable state. Otherwise, we will experience anxiety, depression, menopause and other symptoms that you often hear about in TV commercials. In general, when you want to hit someone with a brick or want to run away because you can't beat them, sympathetic nervous system excitement dominates, which manifests as increased blood pressure, faster heartbeat, and tracheal dilation - all you can see is heavy breathing. When you are leisurely listening to light music or flipping through a magazine, the parasympathetic nervous system (vagus nerve) is dominant, which manifests as a slower heartbeat and tracheal constriction - all you can see is a slower breathing. When the parasympathetic nerve (vagus nerve) is overexcited, weak stimulation that has no effect on normal people can cause bronchial contraction and spasm, increased secretions, and symptoms such as coughing, sputum, and wheezing.

3. Infectious factors

Infection is an important factor in the occurrence and development of chronic bronchitis, mainly viral and bacterial infections. Although infection is closely related to the occurrence and development of chronic bronchitis, there is currently insufficient evidence to show that it is the primary cause. It is only considered to be an important factor in the secondary infection of chronic bronchitis and aggravation of the development of lesions.