Paranasal sinuses are air filled cavities found in the bones of the face. They communicate with the nasal cavity. They are lined with a mucosa. The mucosa lines both the sinuses and the nasal passages.
The mucosa produces a mucous substance that coats and protects it. This mucous substance drains from the paranasal sinus cavities into the nose through small openings. These small openings are found throughout the inside of the nasal cavity. There is one opening for each sinus.
There are four pairs of paranasal sinuses: frontal sinuses, maxillary sinuses, ethmoid sinuses and sphenoid sinuses.
How does sinusitis develop?
Sinusitis begins producing symptoms when when the openings that connect the paranasal sinuses and the nasal cavity become clogged or congested.
When the sinuses become congested, they retain the mucous and the toxins that they produce. Normally, the openings drain this into the nose.
Whenever a fluid is retained within any body cavity, it becomes the perfect breeding ground for germs such as bacteria and fungi. This leads to inflammation in the sinus mucosa.
Consider the healthy versus congested sinus like the difference between a pond and a river.
In a pond, the water is still. It does not flow. This creates an environment where all kinds of things can settle and pollute it.
Whereas a river is flowing water. It is more difficult to pollute because it is moving. Pollutants have a harder time settling in moving water.
It is the same idea with the sinuses.
When they are congested, the openings that connect the sinuses to the nasal cavity become blocked. Mucus and toxins accumulate inside the sinuses, because they have nowhere to go. This also gives germs the time and space to multiply. Whereas if a sinus is functioning normally, mucus and toxins will flow out of it. They won’t have time to make deposits.