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Paranasal sinuses
Paranasal sinuses.
Latin	sinus paranasales
Gray's	subject #223 998
Dorlands/Elsevier	s_12/12739013

Paranasal sinuses are air-filled spaces, communicating with the nasal cavity, within the bones of the skull and face.

Contents 1 Types in humans 2 Development 3 Sinuses in animals 4 Biological function 5 Ailments 6 Other sinuses 7 Etymology 8 External links

Types in humans

Humans possess a number of paranasal sinuses, divided into subgroups that are named according to the bones within which the sinuses lie:

• the maxillary sinuses, also called the maxillary antra and the largest of the paranasal sinuses, are under the eyes, in the maxillary bones.
• the frontal sinuses, superior to the eyes, in the frontal bone, which forms the hard part of the forehead.
• the ethmoid sinuses, which are formed from several discrete air cells within the ethmoid bone between the nose and the eyes.
• the sphenoid sinuses, in the sphenoid bone at the center of the skull base under the pituitary gland.

Development

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.

Sinuses in animals

Paranasal sinuses occur in a variety of animals (including most mammals, birds, non-avian dinosaurs, and crocodilians). In non-humans, the bones occupied by sinuses are quite variable.

Biological function

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 facial expression.
• 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

Ailments

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 relatively 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 cleansing.

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.

Other sinuses

The paranasal sinuses are not the only sinuses within the skull: the mastoid cells in the mastoid bone around the middle ear are also a type of sinus.

Etymology

Sinus is a Latin word meaning a fold or pocket; in particular the front pocket in a toga.

External links

• Paranasal+sinuses at eMedicine Dictionary
• The Anatomy Wiz: CT Paranasal Sinuses

v • d • e General anatomy of head and neck - head Face/Occiput Forehead • Eye (Orbit/Periorbita, Trochlea)  • Ear • Temple • Cheek • Chin • Scalp Nose External nose Nostril • Nasal septum • cartilages (of the septum, Greater alar, Lesser alar, Lateral nasal, Accessory nasal, Vomeronasal)  • Olfactory glands Nasal cavity Nasal concha • Sphenoethmoidal recess • Ethmoid bulla • Semilunar hiatus • Maxillary hiatus • Inferior meatus • Vomeronasal organ • Paranasal sinuses Naso-pharynx Choana - Pharyngeal opening of auditory tube (Salpingopharyngeal fold, Salpingopalatine fold, Torus tubarius) - Pharyngeal tonsil - Pharyngeal recess Mouth/oral cavity Palate/roof of mouth Hard palate • Soft palate • Palatine raphe • Incisive papilla Tongue dorsum (Taste bud, Median sulcus, Terminal sulcus, Foramen cecum, Lingual tonsils) • underside (Frenulum, Plica fimbriata, Sublingual caruncle) • Anterior • Posterior • Glossoepiglottic folds Teeth Permanent (Incisor, Canine, Premolar, Molar)  • Deciduous Oro-pharynx arches/fauces (Palatoglossal, Palatopharyngeal) • Oropharyngeal isthmus • Palatine tonsil • Uvula Salivary glands Parotid gland/Parotid duct • Submandibular gland/Submandibular duct • Sublingual gland/Major sublingual duct Other Lip (Upper, Lower) • Philtrum • Pterygomandibular raphe • Vestibule of mouth Fascia Masseteric fascia - Temporal fascia - Galea aponeurotica

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