Tracheobronchial Tube

The tracheobronchial tube connects the pharynx to the bronchial tree that extends into the terminal bronchioles in the lungs providing an unobstructed pathway for air to enter the body and carbon dioxide to leave the body.

The tracheobronchial tube is a fibrous spiral of smooth muscles that become more closely spaced as they near the terminal bronchioles. The size of the airway can be increased or decreased by relaxing or contracting the bronchial smooth muscle. This is controlled by the parasympathetic nervous system—par-ticularly the vagus nerve.

The vagus nerve releases acetylcholine when it is stimulated, which causes the tracheobronchial tube to contract. This is referred to as bronchoconstriction. The opposite effect is created when the sympathetic nervous system releases epi-nephrine that stimulates the beta2 receptor in the bronchial smooth muscle. This causes the tracheobronchial tube to dilate. This is called bronchodilation. In a healthy patient the sympathetic and parasympathetic nervous systems counterbalance each other to maintain homeostasis.

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