Nasal cavity, paranasal sinuses and pterygopalatine fossa

Question 1

Nasal cavity 1

Answer 1

• Mucous membrane-lined and divided in half by nasal septum
• Scroll-like projections (turbinates) increase surface area of the nasal cavity (have inferior, middle, and superior turbinates)
• Inferior turbinate bone (concha) is its own structure, but middle and superior turbninates are derived from ethmoid bone
• Lateral walls of the nasal cavity composed of many bone

Question 2

Nasal cavity 2

Answer 2

• Nasal septum composed of vomer (inferior) and perpendicular plate of ethmoid (superior) and cartilaginous (anterior)
• The floor of the nasal cavity is the hard palate and consists of the palatine process of the maxilla (anterior) and the horizontal plates of the palatine bones (posterior)
• The roof of the nasal cavity is made up of the cribriform plate of the ethmoid bone

Question 3

Relationships of the nasal cavity to paranasal sinuses

Answer 3

• Frontal sinuses in frontal bone just above the anterior region of the nasal cavity
• Maxillary sinuses are in the maxilla just lateral to the nasal cavity
• The ethmoid air cells are within the ethmoid bone just lateral to the upper region of the nasal cavity and medial to orbits
• The sphenoid sinus lies w/in the body of the sphenoid bone just posterior to the ethmoid air cells

Question 4

Lateral walls of nasal cavity 1

Answer 4

• Air space below and lateral to each turbinate is a meatus
• There is a superior, middle and inferior meatus on each side
• Excess tears drain thru the nasolacrimal duct and into the inferior meatus
• The middle meatus receives drainage from the maxillary, frontal, and ethmoid air cells (anterior group) via the semilunar hiatus

Question 5

Lateral walls of nasal cavity 2

Answer 5

• Frontal drains to most superior, ethmoid drains to the middle, and maxillary drains to most inferior aspect of the semilunar hiatus
• The posterior group of the ethmoid air cells drains into the superior meatus
• The sphenoid sinus drains thru the sphenoethmoidal recess superior to the superior turbinate

Question 6

Pterygopalatine fossa 1

Answer 6

• Small, roughly coned-shaped space btwn the infratemporal region and the nasal cavity
• The sphenoid bone (anterior side of the pterygopalatine fossa) has 6 openings that communicate w/ other regions of the head
• Pterygomaxillary fissure: contains the maxillary artery, as it leaves the fissure and enters the pterygopalatine fossa it gives off 3 terminal branches (infraorbital, sphenopalatine, and descending palatine arteries)

Question 7

Pterygopalatine fossa 2

Answer 7

• Sphenopalatine foramen: contains sphenopalatine artery (terminal branch of the maxillary artery) which supplies posterior 2/3rds of nasal cavity
• Palatine canal: contains the greater and lesser palatine nerves (V2 + para/post of VII), and descending palatine artery
• Superior orbital fissure: contains opthalmic vein, V1, CNs 3, 4, and 6
• Foramen rotundum: opens to pterygopalatine fossa and contains V2 (maxillary nerve)
• Pterygoid canal: contains nerve of the pterygoid canal (continuation of the greater petrosal nerve, para/pre of VII, AKA vidian’s nerve) which exits the canal and synapses at the pterygopalatine ganglion

Question 8

Pterygopalatine ganglion

Answer 8

• 4th of the four pair of parasympathetic ganglia in the head (others: otic, ciliary, submandibular)
• The para/post axons hitchhike on either V2 (to get to the nasal cavity and palates) or on both V2 and V1 (lacrimal nerve to get to lacrimal gland)
• The para/pre cell bodies are in the superior salivatory nucleus and exit the brainstem on VII

Question 9

Course of the para from VII

Answer 9

• Para/pre cell bodies in the superior salivatory nucleus in brainstem
• Exit on the facial nerve-> greater petrosal nerve-> nerve of pterygoid canal-> pterygopalatine ganglion
• Para/post to lacrimal gland course from the pterygopalatine ganglion on branches of V2-> lacrimal nerve-> lacrimal gland
• Para/post to nasal cavity and palate course from the pterygopalatine ganglion on greater palatine nerve (V2)-> nasal and palatine mucosa

Question 10

Sensory innervation of nasal cavity and palate

Answer 10

• The mucosa in these structures is derived from ectoderm and is therefore innervated by somatosensory
• Posterior 2/3rds of the nasal cavity is supplied by the maxillary nerve (V2)- branches of the greater palatine nerve
• The anterior 1/3rd of the nasal cavity is supplied by a branch of the the opthalmic nerve (V1- specifically a branch of the nasociliary nerve)
• All somatosensory cell bodies are in the trigeminal ganglion
• The branches off the pterygopalatine ganglion contain both somatosensory and para/post axons (para from VII)

Question 11

Maxillary nerve distribution

Answer 11

• Innervates the mucosa of the posterior 2/3rds of the nasal cavity and the palates
• Leaves trigeminal ganglion via maxillary nerve then enters foramen rotundum which opens into the pterygopalatine fossa
• In pterygopalatine fossa the somatosensory nerves pass from maxillary thru the pterygopalatine ganglion (w/o synapsing) to course w/in the greater and lesser palatine nerves
• The greater and lesser palatine nerves descend in the palatine canal to reach the mucosa of the hard and soft palates, respectively
• Branches off the greater palatine nerve course anteriorly to supply the posterior 2/3rds of the lateral and medial (nasal septum) walls of the nasal cavity

Question 12

Sensory innervation to the anterior 1/3rd of the nasal cavity

Answer 12

• The branch of the nasociliary nerve (from opthalmic nerve, V1) continues from the orbit down to the anterior 1/3rd of the nasal cavity (both lateral and medial walls)
• This nerve then continues to innervate the skin along the length of the bridge of the nose

Question 13

Olfactory nerve and lacrimal nerve

Answer 13

• Olfactory epithelium is located at the roof of the nasal cavity
• Processes of olfactory nerves in epithelium pass thru cribriform plate of ethmoid bone to synapse w/ secondary neurons in olfactory bulbs located on top of cribriform plate
• The lacrimal nerve (branch of V1 but carrying para/post from VII along w/ the SS from V) continues after reaching the lacrimal gland to innervate the palpebral conjunctiva and skin of the outer eyelid, upper only (frontal nerve also innervates the same targets)
• The bulbar conjunctiva SS is give by the nasociliary nerve (both upper and lower bulbar conjunctiva)

Question 14

Blood supply to nasal cavity 1

Answer 14

• Arteries supplying the medial and lateral walls of the nasal cavity include the sphenopalatine (from maxillary artery), the greater palatine (from maxillary), the facial, and branches of the opthalmic artery
• Nosebleeds (epistaxis) usually are from the anterior 1/3rd of the septum where there are many anastomoses of these arteries

Question 15

Blood supply to nasal cavity 2

Answer 15

• This area represents the anastomosis of arteries from the internal carotid artery (opthalmic) and external carotid (sphenopalatine, greater palatine, and facial)
• The opthalmic and facial arteries supply the anterior most 1/3rd of the nasal cavity
• The sphenopalatine and greater palatine, arteries supply the posterior 2/3rds of the nasal cavity
• The greater palatine artery supplies the soft and hard palates