Sinuses

Question 1

What are the paranasal sinuses?

Answer 1

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

Question 2

What are the functions of the paranasal sinuses?

Answer 2

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

Question 3

Which sinuses are present at birth?

Answer 3

Maxillary and ethmoid

All arise as outpouching if nasal cavity except sphenoid sinus

Question 4

Which sinus is the largest and first to develop?

Answer 4

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

Question 5

Which nerve runs through the maxillary sinus?

Answer 5

Infraorbital runs in roof and anterior wall to supply cheek

Question 6

What is the arterial supply and innervation of maxillary sinus?

Answer 6

Internal maxillary artery

Branches of V2

Question 7

How long do the ethmoid sinuses grow for?

Answer 7

Fluid filled at birth that grow until the age of 12

Question 8

Where do the ethmoid sinuses drain into?

Answer 8

Ethmoid infundibulum

Question 9

What is the arterial supply of the ethmoid sinuses?

Answer 9

Anterior +posterior ethmoidal arteries from the ophthalmic arteries
Sphenopalantine artery from internal maxillary artery

Question 10

Which sinus is the most variable?

Answer 10

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

Question 11

What is Ager Nasi cell?

Answer 11

Anteromost ethmoid cell
Present in 78-98% of individuals
Encountered in dacryocystorhinostomy
Forms early in development

Question 12

Where are the anterior and posterior ethmoidal foramina?

Answer 12

Anterior: 24mm from anterior lacrimal crest
Posterior: 12mm behind anterior
Optic canal: 6mm behind posterior
Important for medial approach to the orbit

Question 13

When does the frontal sinus finish developing?

Answer 13

From age 2 to teenage years

Forms by upward movement of anterior ethmoidal cells

Question 14

Which wall of the frontal sinus is thinnest?

Answer 14

Posterior

Separates sinus from anterior cranial fossa

Question 15

What is the arterial supply of the frontal sinus?

Answer 15

Supraorbital and supratrochlear branches of ophtjalmic artery

Question 16

What is innervation of frontal sinus?

Answer 16

Supraorbital and supratrochlear nerves

V1

Question 17

Where does the sphenoid sinus originate from?

Answer 17

Nasal embryonic lining
Extension of ethmoid sinuses into sphenoid bone
Full size by teenage years

Question 18

Which walls of the sphenoid sinus are thinnest?

Answer 18

Antero-superior wall and roof of sphenoid sinus

Question 19

Where is the ostium in the sphenoid sinus?

Answer 19

Anterosuperior surface of sphenoid face, medial to superior turbinate

Question 20

What is the arterial and nerve supply of the sphenoid sinus?

Answer 20

Sphenopalatine and ethmoidal arteries

Innervated by V1 and V2

Question 21

What are the 3 patterns of sphenoid sinus?

Answer 21

Variably pneumatized

Sellar, pre-sellar or conchal

Question 22

What is the clinical relevance of the onodi cell?

Answer 22

Extension of ethmoid sinus to surround optic nerve
Present in 8-13% of individuals
Can have isolated disease which can affect optic nerve

Question 23

What is the microscopic anatomy of the sinuses?

Answer 23

4 types of epithelium
Ciliated columnar- move mucus blanket
Non ciliated- increase humidification
Goblet cells- secrete glycoproteins
Basal cells

Question 24

How does the autonomic nervous system affect mucus?

Answer 24

Sympathetic- thinner and watery

Parasympathetic- thicker

Question 25

How does mucociliary clearance occur?

Answer 25

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

Question 26

Why is a side effect of DCR sinusitis?

Answer 26

Surgery occurs close to osteomeatal complex where mucocilary clearance occurs