Nasal Cavity & Paranasal Sinuses

Question 1

Describe the relationship between the upper respiratory tract and GI tract.

Answer 1

They share a common proximal pathway:

• Nasal cavity superior to the oral cavity (divided by hard palate bone)
• Oesophagus being posterior to the trachea
• > why you can feed a nasogastric tube through the nasal cavity + into the stomach

Question 2

Describe the structure of the upper respiratory tract.

Answer 2

Nasal cavity includes 2 nares divided by the septum -> posterior part of nasal cavity is choanae (entrance to nasopharynx) -> nasopharynx -> oropharynx (posterior of oral cavity) -> laryngopharynx (posterior to larynx)

Question 3

What is the nasal cavity?

Answer 3

Wedge shaped region between the orbits that extends from nares to choanae

Question 4

What are the names of the 3 bony shelves in the nasal cavity and the spaces underneath them (from top down)? What is the epithelium covering them and their vascular?

Answer 4

1. Superior concha (part of ethmoid bone)
   Superior meatus
2. Middle concha (part of ethmoid bone)
   Middle meatus
3. Inferior concha (own bone)
   Inferior meatus
   All covered in mucus epithelium + very vascular

Question 5

In what direction to the concha project?

Answer 5

Inferomedially from lateral wall on both sides relate to the nasal septum

Question 6

What are the functions of the nasal cavity? What are the main characteristic features that allow it to do this?

Answer 6

Warms, humidifies + filters incoming air because there is highly vascular mucosal tissue covering the bony concha projections + concha also create turbulent air flow via curled projections

Amplifies sound + produces resonance in our voice too

Polyps, infection + congestion in the nasal cavity will therefore disrupt these functions (e.g. inferior meatus polyp or congested mucosa)

Question 7

What are the 3 mucosa lined regions of the nasal cavity (in order of the furthest to outside world and innermost structure)? What are their functions?

Answer 7

1. Nasal vestibule region: hair bearing skin (stratified squamous epithelium) - filtering + abrasion resistance
2. Olfactory region: olfactory lining + nerve endings - smell + interpretation of smell
3. Respiratory region: pseudostratified columnar ciliated epithelium + mucus producing goblet cells

Question 8

What is the nasal septum composed of? What effects can a deviated septum have?

Answer 8

Bones + cartilage (allows nose to be flexible)

Nasal cavity functions will be disrupted e.g. warmth, air flow, filtering + voice resonance

Question 9

The inferior portion of the nasal cavity called the __ makes up the superior part of the hard palate of the oral cavity.

Answer 9

Vomer

Question 10

What would be the name of a defected hard palate? What are the effects of this?

Answer 10

Cleft palate

Communication between entire nasal cavity + oral cavity

Question 11

What is the main role of the concha? What would you see if you looked up a patients nasal cavity at first glance?

Answer 11

Increase surface area
The inferior concha would be the first structure you would see as its the biggest, the nasal septum would be in the middle + the middle concha will be more posterior and superior

Question 12

Describe the bloody supply to the nasal cavity.

Answer 12

High vascular + anastomotic

Multiple vessels anastomose on the anterior nasal septum = little areas/Kiesselbach plexus (vessels aren’t hard to damage so can bleed if nose is picked too much)

Arteries + veins present so flow of bleed will change i.e. slow bleed if from vein + vice versa

Question 13

What is the sensory innervation of the nasal cavity?

Answer 13

Trigeminal (CN V) nerve has 3 divisions: Va, Vb + Vc

Olfactory (CN I) nerve endings go through cribriform plate in ethmoid bone inferior to the cranial cavity

Question 14

What are the 3 divisions of the trigeminal nerve? How does this explain pain referral of the face?

Answer 14

Va = Opthalmic (pain referral to/from frontal head)

Vb = Maxillary (pain referral to/from maxillary teeth)

Cv = Mandibular (pain referral to/from jaw/temples)

Question 15

If someone has sustained facial trauma that has fracture their cribriform plate, what can happen? Why?

Answer 15

Protrusion of the cribriform plate up into the cranial cavity will cause the patient to experience CSF rhinorrhoea + anosmia as it will hit the meningeal coverings separated by CSF + the olfactory nerve endings

Question 16

Why is the nasal cavity not isolated where it sits? What structure is near it + what problems can arise here?

Answer 16

The lacrimal sac in the corner of the eye drains into the nasolacrimal duct which opens into the inferior meatus

• Blocked duct (e.g. cold/congestion) -> epiphora as cannot drain quick enough
• Mechanical obstruction/blockage at any point along structure (e.g. polyp, eyelash, trauma) -> dacrostenosis
• Inflammation (due to blockage) -> dacryocystitis

Question 17

What are the 4 air-filled cavities within nasal cavity i.e. paranasal air sinuses?

Answer 17

1. Frontal
2. Ethmoid
3. Maxillary
4. Sphenoid
   (named after bones of skull they are found in - can use orbitals as landmarks to find them in X-ray)

Question 18

What type of epithelium lines the paranasal air sinuses? Why do they need to drain and where do they drain into?

Answer 18

They are lined with respiratory epithelium that produces mucus due to goblet cells so must drain into nasal cavity where you will either blow it out of your nose or swallow it

Question 19

Where/how do the paranasal sinuses drain? What’s special about maxillary drainage?

Answer 19

Frontal (x2), ethmoid + maxillary: middle meatus
Sphenoid: above superior concha

Maxillary sinus drains in a superior + posterior direction in the nasal cavity - only sinus that does not drain with gravity (why laying down when you have a cold is helpful for congestion)

Question 20

What is the structure of the maxillary sinus? What is in close relation to it? How would poor drainage affect it?

Answer 20

Base, floor, reef, apex (pointing to zygoma) + lateral wall = huge structure (can be seen as huge dark circles on CT scan anterior of head)

Close relation to maxillary nerve therefore, may feel pain in the sinus if you have maxillary tooth pain

Septa can affect drainage -> infection, inflammation, sinusitis (mucosa can become inflamed by 3cm massively impeding drainage)

Question 21

What is the sphenoid sinus drainage? What is it close too? Explain why this is important.

Answer 21

Drains into sphenoethmoidal recess right above superior concha next to the bony crevesce + cranial cavity

Important as you can access part of the brain through this sinus in a less invasive but direct way e.g. in pituitary gland surgery

Question 22

Where does the frontal sinus drain?

Answer 22

Via the frontonasal duct into the middle meatus

Question 23

What is in the ethmoid sinus and what seperates it from the orbits? Explain why this is important.

Answer 23

Multitude of tiny spaces and ethmoid air cells - different to other sinuses

Separated from orbits by only a thin plate of bone so infection can spread here causing peri-orbital cellulitis

Question 24

Where do the 4 paranasal sinuses drain? What is their sensory innvervation?

Answer 24

Drainage of maxillary, ethmoid + frontal sinus = hiatus semilunaris (middle meatus)
Sphenoid = sphenoethmoidal recess

Ethmoid, frontal + sphenoid = CN Va (ophthalmic)
Maxillary = Cn Vb (maxillary)

Question 25

What are the 2 structures underneath the middle concha in the middle meatus space?

Answer 25

Ethmoid bulla

Hiatus semilunaris