From Wikipedia, the free encyclopedia
Paranasal sinuses are air-filled spaces,
communicating with the nasal cavity, within the bones of the skull and face.
Humans possess a number of paranasal sinuses, divided into
subgroups that are named according to the bones within which the sinuses lie:
The paranasal air sinuses are lined with respiratory epithelium
(ciliated pseudostratified columnar epithelium).
Paranasal sinuses form developmentally through excavation of
bone by air-filled sacs (pneumatic diverticula) from the nasal cavity. This
process begins prenatally, and it continues through the course of
an organism's lifetime
Paranasal sinuses occur in a variety of animals (including most
non-avian dinosaurs, and
crocodilians). In non-humans, the bones
occupied by sinuses are quite variable.
The biological role of the sinuses is debated, but a number of
possible functions have been proposed:
- Decreasing the relative weight of the front of the skull, and
especially the bones of the face. The shape of the facial bones is
important, as a point of origin and insertion for the muscles of
- Increasing resonance of the voice.
- Providing a buffer against blows to the face.
- Insulating sensitive structures like dental roots and eyes from
rapid temperature fluctuations in the nasal cavity.
- Humidifying and heating of inhaled air because of slow air
turnover in this region.
For more details on this
topic, see Sinusitis
The paranasal sinuses are joined to the nasal cavity via small orifices called ostia. These become blocked easily by
allergic inflammation, or by swelling in the nasal lining which
occurs with a cold.
If this happens, normal drainage of mucus within the sinuses is disrupted, and sinusitis may occur.
These conditions may be treated by drugs such as pseudoephedrine, which reduce moisture
in the sinuses, or by traditional techniques of nasal
Malignancies of the paranasal sinuses comprise approximately
0.2% of all malignancies. About 80% of these malignancies arise in
the maxillary sinus. Tumors of
the sphenoid and frontal sinuses are extremely rare.
The paranasal sinuses are not the only sinuses within the skull:
cells in the mastoid bone around the middle ear are also a
type of sinus.
Sinus is a Latin word meaning
a fold or pocket; in particular the front
pocket in a toga.
and neck, upper RT: Nose (TA A06.1, GA 10.992)
|respiratory system navs: anat
noncongen/congen/tumors, symptoms+signs/eponymous, proc