As air passes through the nose, it gets heated by finger-like projections called turbinates. Turbinates are bony structures that act as baffles, directing the passage of air along a specific path. The turbinates also act as radiators, adding warm, moist heat to the air as it passes. They also help increase the surface area of the nose to make the heating and humidifi - cation process more efficient (Diagrams 3a and 3b).
The bones of the turbinates are encased in vascular tissue that is covered by a mucous membrane. This vascular tissue swells or shrinks in response to alterations in the body’s blood flow. Positional changes (lying down versus standing, lying on your back versus lying on one side or the other), endocrine changes (hormonal changes during menstrual cycles, puberty, menopause, pregnancy, or aging), increased carbon dioxide intake, alterations in blood flow, or even normal daily living (including the foods and fluids that you eat and drink and medicines that you may be taking for other ailments) can affect the swelling of this tissue.
On each side of the nose there are three sets of turbinates: the inferior (lower) turbinates, the middle turbinates, and the superior (upper) turbinates. Some people are born with a fourth set called the supreme (highest) turbinates. Below each turbinate is a space or opening, called a meatus. The inferior turbinates are the largest and lie parallel to the bottom of the nose. The tear duct (nasolacrimal duct) drains into the area below the inferior turbinate, called the inferior meatus. The nasolacrimal duct connects the inside of the eye with the nose. It carries tears from our eyes and passes them into our nose. This is why when you cry your nose runs.
The middle turbinate is located above the inferior turbinate. Below the middle turbinate is a space called the middle meatus, where the ethmoid sinus lies. The superior turbinate is usually the smallest turbinate, unless the supreme turbinates are present, which are even smaller. Under the superior turbinate is the superior meatus and below this is the sphenoethmoidal recess (a space between the sphenoid sinus and the posterior ethmoid (back part of the ethmoid sinus), and this is where the sphenoid sinus and the posterior ethmoid sinus drain.