The Trachea (Windpipe)
The trachea or windpipe as it is often called, is a continuation of the larynx and extends downwards towards the lungs, where it splits to form two bronchus, with one traveling to each lung. In an adult, it is approximately 10-11 cm long and sits centrally down the front of the neck. Behind the trachea, is the Oesophagus.
The trachea is made up of 16-20 C shaped rings of Cartilage, which lie one beneath the other, joined by tissue and muscle. The soft tissue of the back wall, which makes the C a closed shaped, is joined to the Oesophagus.
The trachea is cleverly designed. It somewhat resembles a vacuum hose, with the coils being the Cartilage and the plastic being the tissues and muscle. Like the hose, the trachea is designed to stretch and bend, whilst still keeping the tube open. The arrangement of cartilage and tissue prevents kinking and obstruction no matter which way the head or neck may move. The lack of cartilage on the side joining the oesophagus, allows for easy swallowing, whilst still taking up only a small amount of space when not in use by sitting almost flat.
Like the nose, the trachea is lined with small hairs (cilia), these act by moving any mucus that touches them in an upwards direction towards the Larynx, where they can easily be coughed out or swallowed.
In addition to the cilia, the trachea is also lined with sensitive nerves. The purpose of these nerves is to watch for irritation. If irritated, they send a message to the brain, which creates a reflex action, somewhat like moving your hand if you touch something hot. The first part of the reflex is to take a deep breath; the glottis (The vocal section of the Larynx) then closes. This is quickly followed by the abdominal and chest muscles working, to push the air out of the lungs, under a high pressure. This is referred to as coughing and its main purpose is to remove mucus and foreign materials from the trachea, into the safety of the mouth.
Normal Anatomy of the Airways.
Larynx (Voice Box)