Paranasal Sinuses: Anatomy and Function Dr. Jihan AL Maddah

Sinus Anatomy Overview 7 bones 4 paired sinuses 4 turbinates 3 meati Drainage system Nervous supply Vascular supply Related structures

Sinus Development Max: 1=newborn, 2=12 yrs, 3=adult sphenoid: 1=newborn, 2=3yo, 3=5yo, 4=7yo, 5=12yo, 6=adult, (7=presphenoid) frontal: 1=nasal septum, 2=middle nasal concha, 3=orbit, 4=newborn, 5=1yo, 6=4yo, 7=7yo, 8=12yo, 9=adult

Bony Structure Ethmoid Maxilla Palatine Lacrimal Pterygoid plate of Sphenoid Nasal Inferior Turbinate

Arterial Supply External Carotid Internal Carotid Maxillary A. Sphenopalatine Internal Carotid Ophthalmic A. Ant. Ethmoid Post. Ethmoid Supraorbital Supratrochlear

Innervation

Neurovascular Supply

Drainage All sinus ostia drain into the nares at locations beneath the middle and superior turbinates. The posterior ethmoid and sphenoid sinuses drain into the superior meatus below the superior turbinate. Osteomeatal complex: The ostia of the maxillary, anterior ethmoid, and frontal sinuses share a common site of drainage within the middle meatus. The common drainage pathway of the frontal, maxillary, and anterior ethmoid sinuses within the middle meatus allows relatively localized mucosal infection processes to promote infection in all these sinuses.

Osteomeatal Complex Middle meatus Maxillary Sinus Ostium Anterior Ethmoid Drainage

Sinus Drainage Schema

Anterior and posterior ethmoid sinuses are composed of multiple air cells separated by thin bony partitions. Each cell is drained by an independent ostium that measures only 1-2 mm in diameter. The sphenoid sinuses sit immediately anterior to the pituitary fossa and just behind the posterior ethmoid.

Maxillary Sinus

Frontal Sinus Development Frontal bone at birth Age 5

Sphenoidal Sinus Development Arise within the nasal capsule (no pouch) Age 3 begins to pneumatize

Sphenoid Sinus

Sphenoid Ostium Sphenoethmoid Recess Sphenoid Rostrum

Microscopic Anatomy Mucosa Goblet Cells Basement membrane Cilliated columnar epithelial cells Noncilliated columnar cells Basal cells Goblet Cells Glycoproteins—viscosity and elasticity Basement membrane Submucosal glands

Microscopic Anatomy

Mucous Blanket Two layers Function Superficial layer Sol layer Superficial layer traps bacteria and particulate matter. Enzymes, antibodies, immune cells

Mucociliary Transport Directional Flow of Mucous Toward the choanae Ostium drainage

Function of Paranasal Sinuses Humidifying and warming inspired air Regulation of intranasal pressure Increasing surface area for olfaction Lightening the skull Resonance Absorbing shock Contribute to facial growth