The Anatomy of Sleep Apnea and Snoring
Obstructive sleep apnea (OSA) is a disorder characterized by obstruction of the upper airway during sleep. This page briefly describes some of the anatomic structures of the upper airway that play a big role is OSA. Other pages in this series describe (1) diagnosis and test of OSA, (2) treatment of OSA with lifestyle and dental appliances, (3) treatment with airway support using CPAP, and (4) treatment with surgical techniques.
Review of the Anatomy
The image to the left shows the mouth. Important structures in OSA are the uvula (U), the soft palate (SP), and both tonsils (T). The roof of the mouth is called the palate. In the front, the palate is made of bone and is called the hard palate. Farther back the bone ends, and the palate is made up of soft tissue. This part is called the soft palate. The small tag of tissue that hangs down in the middle of the soft palate is the uvula.
The soft palate is extremely important in preventing food and liquids from going back up into the nose when we swallow. It also helps to prevent excessive air flow through the nose during speech. For most sounds in American English the palate is closed and air flow through the nose is minimal. Exceptions to this are the sounds "m", "n", and "ng".
In infancy, the tonsils play a role in the development of the immune system, but they can be removed at an early age without any effect on our ability to fight diseases. Tonsils usually decrease in size as we pass through childhood, but in some individuals the tonsils can be so large that the nearly touch in the middle. When they are this large, they often can cause airway obstruction.
What about the uvula?
The exact function of the uvula is still not really known. In fact, a recent article in one of the otolaryngology journals was called "The Mystery of the Uvula". Certain languages require the uvula in order to produce sounds specific to that language (English is not one of these languages) The uvula also helps close off the palate, as described above, when we speak and swallow. Finally, some people feel that the uvula may play a small role in clearing saliva from the oral cavity.
Disturbances in airflow of air through the nose can also worsen OSA. The nasal cavity extends farther back than most people realize, as shown in the image to the left. The large black arrows show where enters when we inhale. Within the nose are structures called the turbinates. There are three or four turbinates, and the images has labeled the inferior turbinate (IT) and the middle turbinate (MT). These turbinates increase the effective surface are of the lining of the nose, which helps the nasal cavity warm, humidfy, and clean the air as it passes through the nose into the lungs. If the turbinates are extremely large, they can block airflow through the nose.
Note that the floor of the nose is the hard and soft palate, and that in the back the nasal cavity opens into the rest of the throat. The "U" in this illustration is the uvula.
The letter "T" shows the anterior tongue, the part of the tongue that we can see in our mouth. The tongue also extends back quite a bit; the rearmost part is called the base of tongue ("BoT"). Looking at the diagram, it is easy to see that if we are lying on our back, as the throat muscles relax the base of tongue can fall back and block part of the airway.