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What Are the Sinuses? - Definition & Terminology

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  • 0:01 Bones & Empty Space
  • 0:45 Paranasal Sinuses
  • 1:55 The Names of the Sinuses
  • 3:06 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

This lesson will define the paranasal sinuses (ethmoid sinuses, frontal sinuses, sphenoid sinuses, and maxillary sinuses), as well as their functions and locations.

Bones & Empty Space

One of the reasons why birds can soar so high in the sky is because their bones are very light. Their bones are light because they have a lot of empty spaces within them. In general, humans do not have bones with a lot of empty space.

However, some of the bones of the skull and face are made lighter thanks to empty spaces within them. These empty spaces also provide resonance for speech and produce mucus to lubricate the nasal cavity.

What are these empty spaces called? The paranasal sinuses. Let's go over them.

Paranasal Sinuses

The paranasal sinuses are paired, mucous membrane-lined, air-filled cavities within some of the bones of the skull and face. Each cavity is called a sinus, and the word 'paranasal' is broken down as follows. 'Para-' means 'near', 'nas'/'naso' refers to the 'nose' and '-al' tells us it is 'pertaining to'. So, it boils down to this: these are empty spaces near the nose; that's it. And the combining form sinus/o pertains to the sinuses.

Again, these sinuses have numerous functions. They:

  • Produce a thick fluid, called mucus, from the mucous membranes that line them. This helps lubricate the nasal cavity and humidify the incoming air.
  • Act to heat the air we inhale
  • Provide resonance for our voices
  • Act sort of like air bags in the case of facial trauma as they crumple from the impact
  • Lighten the bones of the skull and thus the head itself

The Names of the Sinuses

The paranasal sinuses are named for the bones of the skull and face in which they are located, so their names and locations should be easy to recall if you already know your anatomy.

First, we have the frontal sinuses, which are cavities located in the frontal bone. This is the big bone right above your eyebrows that makes up your forehead. These sinuses sit above the eyes.

Next, there are the sphenoid sinuses, cavities located in the sphenoid bone. The sphenoid sinuses sit deep within the skull, behind the nose and eyes.

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