ASSIGNMENT 5: PARA-NASAL SINUSES & NITRIC OXIDE

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PARA-NASAL SINUSES

Para-nasal sinuses are air filled spaces that are located with-in the facial skeleton. All but one of the para-nasal sinuses are paired. The best way to visualize the them is by taking an X-ray. This is shown in the figure below

The sinuses are:

1. Maxillary Sinuses (the largest)

2. Ethmoid Sinuses

3. Frontal Sinuses

4. Sphenoid Sinus (non-paired)

The following figures shows the location of these sinuses.

(M= Maxillary, S= Sphenoid E=Ethmoid)

THE GENERAL SINUS STRUCTURE

The sinuses are lined by pseudo-stratified columnar epithelium, which continues into the nose as nasal mucosa. There are four basic cell types:

Ciliated columnar epithelial cells

Non-ciliated columnar cells

Basal cells

Goblet cells

The ciliated cells have about 50 to 200 cilia which beat at the rate of 800 beats a minute and move mucus at a rate of 9 mm per minute. The cilia help move mucus to the sinus ostium (at times against the gravitational force). The non-ciliated cells help in humidification of air

The goblet cells produce glyco-proteins that help to provide "elasticity" to the mucus. The maxillary sinus has the greatest concentration of goblet cells.

The epithelial layer is supported by a thin basement membrane and beyond that the periosteum.

FUNCTION OF THE SINUSES

Besides the "usual" functions of humidification of air, resonance and reducing the weight of the skull, the sinuses have been discovered to have a strong immunogenic activity thanks to the ciliary function. It has been recently discovered that sinus cells produce Nitric Oxide which help in cilia motility.

Mucus clearance by the cilia is an essential feature of sinus physiology. Mucus accumulated in the sinus cavities can serve as excellent media for bacterial growth and be responsible for sinusitis (inflammation of sinuses)

Your task is to look for evidence that shows that nitric oxide plays a role in normal functioning of the ciliary epithelium in the sinuses and thus prevent bacterial infection in the sinuses.