Airway

From ArticleWorld

The airway is the anatomic pathway that air must take from the external world to the alveoli of the lungs where the oxygen in the air enters the blood stream and is exchanged with carbon dioxide, a waste product of metabolism.

Anatomy

The airway can begin at either the nares in the nose or in the mouth. The advantage the nose has over the mouth is the presence of small hairs that can trap larger particles in the air before they reach the lungs. Behind the nose and mouth is the hollow area called the pharynx. The air then passes past the vocal cords and down the cartilaginous trachea or “air tube”.

The trachea splits into the right and left mainstem bronchi that each provides air to a lung. The mainstem bronchi break up into smaller and smaller bronchial tubes until the tubes become so small, they are called bronchioles. The ends of the bronchioles are clusters of alveoli or air sacs that allow for the diffusion of gases across the thin membranes of the alveoli into the blood stream.

Function

Much of the airway is lined with a membranous surface that contains tiny hair cells called cilia. The cilia actively push debris from the airway of the bronchial tree so that the debris can be trapped in mucus and be coughed out of the trachea and pharynx. The mucus is made by the airway lining and helps deliver debris more easily upward towards the pharynx. Inside the airway are macrophages that engulf bacteria and debris before they reach the lung.

Conditions

There are many conditions that can affect the airway. Asthma or allergies can cause bronchospasm or spasm of the trachea, which happens when the airways contract during exhalation (and sometimes during inhalation), impeding the flow of air. Infections can involve the pharynx (pharyngitis), the trachea (tracheitis), the bronchial tree (bronchitis) or the alveoli (pneumonia). All of these infections can impact the flow of air or the exchange of gases in the lungs. Cystic fibrosis is a condition where the lungs produce too much thick mucus that blocks the alveoli.

Chronic obstructive pulmonary disease (or COPD) is a condition resulting from smoking or other things that damage the lungs. The airways become inflamed, constricted and obstruct airflow. Lung cancer can originate in or obstruct the airway leading to secondary pneumonia and loss of adequate airflow.