TRACHEOBRONCHIAL TUBE
The tracheobronchial tube connects the pharynx to the bronchial tree that ex-
tends into the terminal bronchioles in the lungs providing an unobstructed path-
way 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 air-
way 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 beta 2 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 counter-
balance each other to maintain homeostasis.Upper Respiratory Tract Disorders
Respiratory disorders are divided into two groups: upper respiratory tract disorders
and lower respiratory tract disorders. Upper respiratory tract disorders are called
upper respiratory infections (URIs). These include the common cold, acute rhinitis
(not the same as allergic rhinitis), sinusitis, acute tonsillitis, and acute laryngitis.THE COMMON COLD
The common cold is caused by the rhinovirus invading the nasopharyngeal
tract. The rhinovirus is frequently accompanied by acute inflammation of the
mucous membranes of the nose and increased nasal secretions. This is known as
acute rhinitis.
Adults have between two and four colds per year. Children are more suscep-
tible to colds. The average child has between 4 and 12 colds each year. The
rhinovirus is seasonable: 50% of the infections occur in the winter and 25% dur-
ing the summer. The other 25% occur anytime throughout the year. Although no
one has directly died from the common cold, it does create both physical and
mental discomfort for the person and leads to a loss of work and school.(^256) CHAPTER 14 Respiratory Diseases