Sinuses Flashcards
What are the paranasal sinuses?
Air filled, mucus lined pockets in the facial bones-
Paired and bilateral
Named for the bone that they are in
Each communicates via an ostium with the nasal cavity
What are the functions of the paranasal sinuses?
Humidify inhaled air Lighten skull Resonance of speech Crumple zone in face trauma Protect eyes and teeth from temp change Buffer against increased pressure in upper aerodigestive tract Innate and adaptive immune function
Which sinuses are present at birth?
Maxillary and ethmoid
All arise as outpouching if nasal cavity except sphenoid sinus
Which sinus is the largest and first to develop?
Maxillary
Filled with fluid at birth
Ostium located in superior portion of middle wall
First grows horizontally and posteriorly, then inferiorly
Thinnest point is above the canine tooth
Which nerve runs through the maxillary sinus?
Infraorbital runs in roof and anterior wall to supply cheek
What is the arterial supply and innervation of maxillary sinus?
Internal maxillary artery
Branches of V2
How long do the ethmoid sinuses grow for?
Fluid filled at birth that grow until the age of 12
Where do the ethmoid sinuses drain into?
Ethmoid infundibulum
What is the arterial supply of the ethmoid sinuses?
Anterior +posterior ethmoidal arteries from the ophthalmic arteries
Sphenopalantine artery from internal maxillary artery
Which sinus is the most variable?
Ethmoid
Never the same between individuals
Cells are variably present:
Supraorbital cell=cell above orbit
Frontal bulla=ethmoid cells in floor of frontal sinus
Concha bullosa= cells into middle turbinate
Haller’s cell=cells in roof of maxillary sinus
Onodi cell= cells in sphenoid sinus
What is Ager Nasi cell?
Anteromost ethmoid cell
Present in 78-98% of individuals
Encountered in dacryocystorhinostomy
Forms early in development
Where are the anterior and posterior ethmoidal foramina?
Anterior: 24mm from anterior lacrimal crest
Posterior: 12mm behind anterior
Optic canal: 6mm behind posterior
Important for medial approach to the orbit
When does the frontal sinus finish developing?
From age 2 to teenage years
Forms by upward movement of anterior ethmoidal cells
Which wall of the frontal sinus is thinnest?
Posterior
Separates sinus from anterior cranial fossa
What is the arterial supply of the frontal sinus?
Supraorbital and supratrochlear branches of ophtjalmic artery
What is innervation of frontal sinus?
Supraorbital and supratrochlear nerves
V1
Where does the sphenoid sinus originate from?
Nasal embryonic lining
Extension of ethmoid sinuses into sphenoid bone
Full size by teenage years
Which walls of the sphenoid sinus are thinnest?
Antero-superior wall and roof of sphenoid sinus
Where is the ostium in the sphenoid sinus?
Anterosuperior surface of sphenoid face, medial to superior turbinate
What is the arterial and nerve supply of the sphenoid sinus?
Sphenopalatine and ethmoidal arteries
Innervated by V1 and V2
What are the 3 patterns of sphenoid sinus?
Variably pneumatized
Sellar, pre-sellar or conchal
What is the clinical relevance of the onodi cell?
Extension of ethmoid sinus to surround optic nerve
Present in 8-13% of individuals
Can have isolated disease which can affect optic nerve
What is the microscopic anatomy of the sinuses?
4 types of epithelium Ciliated columnar- move mucus blanket Non ciliated- increase humidification Goblet cells- secrete glycoproteins Basal cells
How does the autonomic nervous system affect mucus?
Sympathetic- thinner and watery
Parasympathetic- thicker
How does mucociliary clearance occur?
Ciliated epithelium beats in a specific direction
Transports mucus against gravity
Mucus may cycle around entire sinus before exiting
2 main drainage sites;
Frontal, maxillary and anterior ethmoids drain into ethmoidal infundibulum->middle meatus-> nasopharynx
Posterior ethmoidal cells and sphenoid sinus-> sphenoethmoidal recess->superior meatus-> nasopharynx
Why is a side effect of DCR sinusitis?
Surgery occurs close to osteomeatal complex where mucocilary clearance occurs
