Sinusitis

Sinusitis is inflammation of the paranasal sinuses - which are pairs of air spaces that surround the nose in the front of the face.

Usually, acute sinusitis can last up to four weeks, subacute sinusitis lasts between 1 to 3 months, and chronic sinusitis lasts more than 3 months.

When you breathe in, air flows through the nostrils and enters the nasal cavity, which is lined by goblet cells that release mucus.

That mucus is salty, sticky, and contains lysozymes, which are enzymes that help kill bacteria.

Nose hairs at the entrance of the nasal cavity get coated with that mucus and are able to trap large particles of dust and pollen as well as bacteria, forming tiny clumps of boogers.

The nasal cavity is connected to four paired paranasal sinuses, named according to the bones in which they lie.

The largest are the maxillary sinuses, found right below the eyes.

Then we have the ethmoidal and sphenoidal sinuses behind the eyes.

Finally, the frontal sinuses are in the forehead, right above the eyes.

The paranasal sinuses act like tiny echo-chambers that help amplify the sound of your voice, which is why you sound so different when they’re clogged with mucus during a cold!

They also allow the inspired air to circulate for a bit so it has time to get warm and moist.

Like the rest of the respiratory tract, the walls of the paranasal sinuses are made up of a mucosal epithelium.

The mucosal epithelium contains goblet cells, which produce mucus to trap small foreign particles, as well as columnar cells, which have cilia, which are tiny little hair like projections that move mucus, draining into the nasal passages.

One of these passages is also called a nasal meatus, and there are three; the superior, middle, and inferior meatus which help drain mucus.

The sphenoidal sinus drains to the spheno-ethmoidal recess, which is a small space in the nasal cavity right above the superior meatus.

The ethmoid sinus can be divided into posterior, which drains to the superior meatus, middle and anterior, both draining into the middle meatus. And finally the maxillary and frontal sinuses drain into the middle meatus.

Most cases of sinusitis are acute; and are the result of a viral infection.

The most common viruses include rhinovirus and parainfluenza virus which cause the common cold, and influenza virus which causes the flu.

Bacterial infections are another cause of acute sinusitis, and the most common bacterial strains are Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis.