anatomy and physiology paranasal sinuses

ANATOMY AND PHYSIOLOGY

OF PARANASAL SINUSES

NAVEEN.K

Air filled spaces present within certain bones of the skull, around the nasal cavities.

“PARANASAL SINUSES”

FRONTAL SINUS Location : In the frontal bone, above and

deep to the supra orbital margin. Average measurements: ht.: 3.2cm, width: 2.4cm, depth: 1.6cm Usually asymmetrical.

Relations :

• Anterior:- skin over the

forehead• Inferior:-

orbit & its contents

• Posterior:- meninges and frontal lobe of brain

NEUROVASCULAR SUPPLY :• Blood supply - Supra orbital artery

• Venous return - Anastomotic veins in supra orbital notch, connecting supra orbital and superior ophthalmic veins.

• Lymphatic drainage – Submandibular nodes.

• Nerve supply - Supra orbital nerve(ophthalmic nerve)

MAXILLARY SINUS :

LOCATION : In the body of maxilla.Also known as antrum of highmore.Largest of all sinuses Pyramidal in shape.Average measurements ht.: 3.3cm, width: 2.5cm, depth: 3.5cm

Relations :

• Anterior:- facial surface of maxilla

• Posterior:-infratemporal and pterygopalatine fossa

• Medial:- middle and inferior meatus

• Floor:- alveolar and palatine processes of maxilla

• Roof:-floor of orbit

Blood supply :

ARTERIAL: • By facial artery branch of ECA. • By infra orbital & greater palatine arteries

branch of maxillary artery which is branch of ECA.

VENOUS: • To anterior facial vein & pterygoid plexus.

NERVE SUPPLY :

• Anterior superior alveolar nerve• Middle superior alveolar nerveBoth from infraorbital nerve

• Posterior superior alveolar nerve from maxillary nerve

SPHENOIDAL SINUS :

LOCATION : Within the body of sphenoid bone.

Paired, separated by a septum.asymmetrical.Average measurements

ht.: 2 cm, width: 2 cm, depth: 2cm

1.Cavernous sinus

IIIrd,

IVth, Vth (ophthalmic and maxillary- divisions) and VIth cranial nerves,

2.Internal carotid artery

Relations - lateral

SUPERIORLY :

Optic chiasmaHypophysis cerebri

FLOOR :

Vidian’s nerve

NEUROVASCULAR SUPPLY :

Blood supply:Posterior ethmoidal and internal carotid arteries.Venous drainage:Pterygoid venous plexuses and cavernous sinus.Nerve supply:Posterior ethmoidal nerve and orbital branches of pterygopalatine ganglion.Lymphatic drainage: Retropharyngeal nodes

ETHMOIDAL SINUSES :

Numerous small interconnecting spaces.LOCATION : Within the ethmoid bone.Divided into three groups Viz., anterior middle posterior

RELATIONS :

• Above: orbital plate of frontal bone.

• Behind: orbital process of palatine bone.

• Anteriorly: lacrimal bone.• Lateral: Lamina papyracea.

• ANTERIOR ETHMOIDAL SINUS : Has 1 to 11 air cells.

NEUROVASCULAR SUPPLY : Anterior ethmoidal nerve and vessels.

LYMPHATICS : Submandibular nodes.

• Some of the important anterior group cells includes

1.Agger nasi cells2.Ethmoidal bulla3.Supraorbital cells4.Frontoethmoidal cells5.Haller cells

• MIDDLE ETHMOIDAL SINUS : Has 1 to 7 air cells. NEUROVASCULAR SUPPLY : Anterior ethmoidal nerve and vessels

and orbital branches of pterygopalatine ganglion.

LYMPHATICS : Submandibular nodes.

• POSTERIOR ETHMOIDAL SINUS : Has 1 to 7 air cells. NEUROVASCULAR SUPPLY : Posterior ethmoidal nerve and vessels

and orbital branches of pterygopalatine ganglion.

LYMPHATICS : Retropharyngeal nodes. Onodi cells – one of the most important air

cell of this group.

Drainage :

DEVELOPMENT OF PARANASAL SINUSES

At about 25 – 28 weeks of gestation, three medially directed projections arise from the lateral wall of the nose.

Between these projections small lateral diverticula invaginate into the primitive choana to eventually form the meati of the nose.

This serves as the beginning of the development of paranasal sinuses.

Sinuses begin developing as small sacculations of the mucosa of the nasal meati and recesses.

As the pouches or sacs develop and grow they will invade the respective bones to form air sinuses and cells.

Development is brought about by resorption of inner surface and apposition on the outer surface by remodelling to accommodate the stresses.

Maxillary sinus - first to be developed and aerated at birth.

shows biphasic growth. The first growth phase during the first three years of life, and the next growth phase occur between 7 – 18 years.

Initially located medial to the orbit, later sinus extends laterally & Inferiorly.

1=newborn,2=12 yrs3=adult

ETHMOID AIR CELLS -develop during puberty and develop slowly until approximately 17-18 years of age.

Pneumatization of this sinus begins during the 4th year of childhood and gets completed by the 17th year of life

SPHENOIDAL SINUS is undeveloped and non-aerated at birth.

Aeration begins at age 3years and then progresses posteriorly.

sphenoid: 1=newborn, 2=3yr, 3=5yr, 4=7yr, 5=12yr, 6=adult,

FRONTAL SINUS is last sinus to develop ,as a direct continuation or by upward migration of anterior ethmoidal air cells.

Remains as a small blind sac within the frontal bone till 2 years of age , from 2 to 9 years secondary pneumatization of frontal bone proceeds.

frontal: 4=newborn, 5=1yr, 6=4yr, 7=7yr,9=adult

FUNCTIONS :

• Decreasing the relative weight of the front of the skull, and especially the bones of the face.

• Increasing resonance of the voice.• Providing a buffer against facial trauma.• 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.

• To provide extended surface for olfaction.• Immunological defense.