Nasal Cavity, Paranasal Sinuses, Maxillary Division of Trigeminal Nerve

Can't stress enough, ORIENT YOURSELF


Bones of the Nasal Cavity

It is always a good idea to learn the bones of a region before proceeding further. The bones of the nasal septum and other landmarks are:
  1. nasal
  2. frontal
  3. ethmoid
  4. sphenoid
  5. vomer
  6. perpendicular plate of ethmoid
  7. maxilla
  8. horizontal process of palatine bone
  9. medial pterygoid plate
  10. occipital condyle
The skeleton of the lateral nasal wall include:
  1. nasal
  2. frontal
  3. ethmoid
  4. sphenoid
  5. maxilla
  6. horizontal process of palatine
  7. superior concha (ethmoid)
  8. middle concha (ethmoid)
  9. inferior concha
  10. sphenopalatine foramen
  11. medial pterygoid plate
  12. pterygoid hamulus of medial plate
Notice that the roof of the nasal cavity is:
  1. nasal
  2. frontal
  3. ethmoid
  4. sphenoid
and the floor:
  • maxilla and its palatine process (5)
  • palatine and it horizontal process (6)

Nasal Septum

Usually when the head is bisected, the nasal septum is either destroyed or left behind on one side.
The nasal septum is made up of the following:
  • perpendicular plate of ethmoid
  • vomer
  • maxilla
  • septal cartilage
The septum and the nasal cavity, in general is highly vascularized. One reason for this might be to warm the air before it reached the bronchi and lungs. The major arteries of the septum are:
  1. anterior ethmoidal (ophthalmic)
  2. posterior ethmoidal (opththalmic)
  3. sphenopalatine (maxillary)
  4. greater palatine (maxillary)
  5. branch of superior labial (facial)
Sensory innervation to the nose is also important in that it provides reflexes (such as the sneeze reflex) to keep foreign particles out of the respiratory system. The sensory nerves to the septum are:
  1. anterior ethmoidal (V1) (nasociliary)
  2. nasopalatine (V2) (maxillary)

Lateral Nasal Wall

ORIENT YOURSELF!

Be sure you know which is front and back and up and down. Look at the lateral wall of the nasal cavity and identify:
  • sphenoethmoid recess (arrow above 1)
  • superior concha (1)
  • superior meatus (tip of arrow)
  • middle concha (2)
  • middle meatus (tip of arrow)
  • inferior concha (3)
  • inferior meatus (ti of arrow)
A meatus is a small space under the concha.
The superior and middle conchae are parts of the ethmoid bone.
The inferior concha is a separate bone of the skull.
Once the most obvious structures are identified, removal of the middle and inferior conchae reveals other items to be identified:
  • cut edges of middle and inferior conchae (1 and 2)
  • hiatus semilunaris (3)
  • ethmoid bulla (bulge formed by ethmoid air cells (4)
  • small bulge formed by the nasolacrimal duct (5) (not always apparent)
In order to get an idea as to the relationship of the nasal cavity to the air sinuses, a frontal section is shown in the image. Again use familiar structures to orient yourself, like the orbits with the optic foramen (black circle). Identify:
  • right and left nasal cavities on either side of the nasal septum made up of the:
  • vomer (7) and
  • perpendicular plate of ethmoid (1)
  • superior, middle and inferior conchae (3-5) with the meatus deep to them
  • large maxillary sinus
  • ethmoid sinuses
  • frontal sinus
Note that the roof of the nasal cavity is made up of the cribriform plate (not labeled) but on each side of (1).
Also note that the floor of the nasal cavity is made up of the palatine processes of the maxilla (6).
The paranasal sinuses are lined with a mucous membrane that secretes a fluid to keep the lining moist. Under normal conditions, the sinuses drain into various parts of the nasal cavity.
  1. sphenoid sinus-->sphenoethmoid recess
  2. frontal sinus-->infundibulum of middle meatus
  3. anterior ethmoid sinus-->middle meatus
  4. middle ethmoid sinus-->ethmoid bulla of middle meatus
  5. maxillary sinus-->middle meatus
One other structure empties into the nasal cavity and the is (6) the nasolacrimal duct. You can see that this duct is close to the front of the nasal cavity and therefore should realize why your nose runs when you cry. This duct carries away extra tears.
     You should also realize that when the drainage pores are closed off due to irritation, the mucous can no longer drain out of the sinuses, they fill up and cause pressure which can then cause headaches (sinus headaches).
    Sinus medication reduces the swelling so that the mucous can drain.
Continuing to work you way laterally, you can remove the bone further and open up the maxillary sinus. You can also see the nasopalatine nerve (1) emerging through the sphenopalatine foramen. Once the foramen is identified, you can then see a small bulge formed by the bony greater palatine canal. If this is broken down, you would see the greater palatine nerve and artery in the canal.
After more of the lateral nasal wall has been removed, you can see the major nerve coming into this region, the maxillary division of the trigeminal.
Now identify:
  1. infraorbital nerve
  2. posterior superior alveolar nerve
  3. pterygopalatine ganglion (parasympathetic)
  4. greater palatine nerve
  5. lesser palatine nerve
  6. cut nasopalatine nerve
  7. nerve of the pharyngeal canal
All of the nerves are sensory branches of V2. The pterygopalatine ganglion is suspended from V2 by two sensory roots. Since the ganglion is parasympathetic, there are preganglionic neurons feeding into it from the facial nerve (greater petrosal branch) that synapse at this point then continue onward as postganglionic neurons. Their destination is the lacrimal nerve and reach there by rejoining the maxillary nerve through a sensory root, hopping onto the zygomatic nerve (V2), running up the lateral side of the orbit to jump onto the lacrimal nerve (V1) and then to the lacrimal gland to produce tears.
As you go posterior to the inferior concha, you enter the nasopharynx. The roof is the body of the sphenoid, the floor is the soft palate and it is open to nasal cavity anteriorly and pharynx posteriorly. When the mucous membrane is carefully removed, you can see the small muscles of the soft palate and upper pharynx. Landmarks are the tubal elevation (torus tubarius) and the uvula (u).
The muscles are:
  1. tensor palati
  2. levator palati
  3. palatopharyngeus
  4. salpingopharyngeus
To identify the tensor, first feel for the medial pterygoid plate and find its posterior border. The muscle is located there. You might see a small artery at this site, the terminal part of the ascending palatine artery (external carotid)
     The palato- and salpingopharyngeus muscles join the stylopharyngeus to form the longitudinal muscles of the pharynx. The help elevate the pharynx when you swallow.

 
 
The major sensory innervation to the nasal cavity is from branches of the maxillary division of the trigeminal (nasopalatine, infraorbital, greater palatine). Other sensory branches are from the ophthalmic division (anterior ethmoidal nerve). Any secretory glands of the nasal cavity are supplied by branches of the pterygopalatine ganglion. The olfactory epithelium in the roof of the nasal cavity is innervated by the olfactory nerve (I) and receives smell sensations.
The major arterial supply to the nasal cavity are from the ophthalmic and maxillary arteries by way of anterior and posterior ethmoidal branches and sphenopalatine branches respectively.

Table of Muscles

Muscle
Origin
Insertion
Action
Nerve supply
tensor palati scaphoid fossa of pterygoid fossa aponeurosis of soft palate elevates and tenses soft palate V3
levator palati apex of petrous temporal bone and auditory tube aponeurosis of soft palate pulls soft palate up and back X
palatopharyngeus aponeurosis of soft palate wall of pharynx elevates pharynx X
salpingopharyngeus cartilage of auditory tube wall of pharynx elevates pharynx X

Items to Remember in this Lesson

Bones

nasal
frontal
ethmoid
crista galli
perpendicular plate
superior concha
middle concha
sphenoid body
medial pterygoid plate
hamulus
inferior concha
maxilla
palatine processes
palatine bone
horizontal process

Air sinuses

frontal
sphenoid
ethmoid
maxillary

 Muscles

tensor palati
levator palati
palatopharyngeus
salpingopharyngeus

Muscles

tensor palati
levator palati
palatopharyngeus

Nerves

V2
greater palatine
lesser palatine
nasopalatine
infraorbital
posterior sup. alveolar
 

Muscles

tensor palati
levator palati
palatopharyngeus

Nerves

V2
greater palatine
lesser palatine
nasopalatine
infraorbital
posterior sup. alveolar

Nerves

V2
greater palatine
lesser palatine
nasopalatine
infraorbital
posterior sup. alveolar

Arteries

sphenopalatine
descending palatine

 

Pharynx   Oral Cavity & Paranasal Sinuses


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