Wednesday, 21 September 2011

What is the biological function of the paranasal sinuses?

In clinic yesterday I saw a patient with headache and a mucocoele in one of the paranasal sinuses. Given how many medical problems are associated with the paranasal sinuses I asked the students sitting in with me about what the biological function of the paranasal sinuses is. The responded by stating that the sinuses make the skull lighter and improve the resonance of spoken speech.

A quick look at the wikipedia lists the following:
  1. Decreasing the relative weight of the front of the skull, and especially the bones of the face.
  2. Increasing resonance of the voice.
  3. Providing a buffer against blows to the face.
  4. Insulating sensitive structures like dental roots and eyes from rapid temperature fluctuations in the nasal cavity.
  5. Humidifying and heating of inhaled air because of slow air turnover in this region.
I suspect all of these are acquired secondary functions. However, the main evolutionary driver is their role as a heat exchanger in relation to the carotid rete to cool the blood going to the brain. Have you heard of a rete? if not, please read the entry on this the section on our wiki on evolutionary neurology

Level 1: What are the biological functions of paranasal sinuses? Answer

Level 3: What is a carotid rete? Answer

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