Nasal Cavity and Paranasal Sinuses Flashcards
What is the nasal cavity composed of externally?
bone
cartilage
muscle
What are the bones of the external nose?
extensions of the skull
* Nasal bones
* Frontal processes of
maxillae
What are the cartilages of the nose?
- Septal cartilage
- Major & minor alar
cartilages
What are the muscles overlying the bone and cartilage?
- Nasalis
- Depressor septi nasi
- Levator labii superioris alaeque nasi
What are the paired cavities seperated by?
nasal septum
How is the nasal cavity seperated from the oral cavity?
hard palate (floor)
What are the anterior apertures of the nasal cavity?
nares
What are the posterior apertures of the nasal cavity?
choanae
which open into the nasopharynx
What receptors does the nasal cavity have?
olfactory responsible for smell
How is inhaled air warmed, moistened and filtered?
by the mucous membrane of the nasal cavity
Where does olfaction occur?
in upper part of the nasal cavity where airflow is diverted especially when “sniffing ”
What is the hard palate made of?
- Palatine process of maxilla
- Horizontal plate of the palatine bones
What is at the floor of the cavity?
hard palate
nares
incisive canals (nasopalatine canals)
nasal crest
What do the incisive canals connect and what do they contain?
- Connection between nasal & oral cavities
- Contains the nasopalatine nerve & greater palatine artery
What is the nasal crest?
what attaches to it
- Ridge formed at the connection of paired maxillae & palatine bones
- Attachment of the vomer of the nasal septum
What is the medial wall of the nasal cavities?
nasal septum
What forms the nasal septum?
- Septal cartilage
- Perpendicular plate of
the ethmoid bone - Vomer
What is septal deviation and how is it corrected?
- Septum is displaced away from the midline
- The extent of displacement can range from mild to severe
- This can be due to a birth defect or, most commonly, caused by injury
- It means that the nasal cavity on one side is obstructed causing symptoms such as snoring, difficulty breathing through the nose, nosebleeds
- It can be corrected surgically
Why is the roof narrower than the floor?
due to the wedge shape of the nasal cavity
What is the highest point of the cavity formed by?
cribriform plate of the ethmoid bone
What does the cribriform plate have?
many foramina to allow the passage of the olfactory nerves into the nasal cavity from the olfactory bulb on the base of the brain
What is the anterior roof formed by?
- Nasal bones
- Nasal spine of the frontal bone
What is the posterior roof formed by?
sphenoid bone
What are olfactory nerves anchored by?
by dura as they pass through the cribriform plate
Where are olfactory nerves distributed to?
to the roof & upper aspect of the nasal cavity
What can trauma/pathologies causing the brain and olfactory bulb to move do?
may tear the olfactory nerves causing anosmia
What can fractures of the cribriform plate cause?
CSF rhinorrhoea
What are the structures of the lateral wall?
nasal bone
lacrimal bone
lateral process of septal cartilage
major alar cartilage
minor alar cartilage
inferior concha
middle concha
superior concha
perpendicular plate of palatine bone
medial petrygoid plate of sphenoid bone
ethmoid
What are the features of the ethmoid bone?
the ethmoid bone is a major component of the nasal cavity
It has a left & right ethmoidal labyrinth with a single, midline perpendicular plate & cribriform plate
The ethmoidal labyrinth projects two of the three conchae into the nasal cavity; the superior & middle conchae
What is underneath the conchae?
the corresponding meatus
What does the structural arrangement of the conchae create?
various air streams, increasing the surface area between the lateral wall of the nasal cavity & the inspired air
What is the arterial supply of nasal cavity?
external carotid, internal carotid/opthalmic artery
ECA
Maxillary - sphenopalatine, greater palatine
Facial - superior labial, lateral nasal
ICA
Ophthalmic - anterior and posterior ethmoidal
What do the anterior and posterior ethmoidal arteries form and why is this area significant?
These vessels form many anastomoses, especially in the anterior septal region & this is an area in which nosebleeds can commonly occur
What is the venous drainage of the nasal cavity?
Veins tend to follow arteries
* Veins that follow arteries of the maxillary artery drain into the pterygoid plexus
* Veins that follow arteries of the facial artery drain into the facial vein
* Veins that follow ethmoidal arteries drain into the ophthalmic vein & subsequently the cavernous sinus
What are the paranasal sinus and what is their role?
frontal, ethmoidal, maxillary and sphenodial
- Hollow air-filled cavities
- Increase surface area aiding
efficient “air conditioning” - Lighten the skull
- Add resonance to the voice
What shape is the maxillary sinus, where does it drain and why is this clinically significant?
pyramid shaped
- The maxilla sinus drains into the middle meatus at the semilunar hiatus
- The drainage opening for the maxillary sinus is positioned high up, near the top of the sinus, which means the sinus floor is lower than its drainage point.
- As a result the maxillary sinus is prone to chronic infections as gravity doesn’t assist much in draining the mucus out of the sinus.
What could extration of maxillary molar teeth cause?
what is this called?
might damage the maxillary sinus floor
* This could create an opening between the maxillary antrum & oral cavity (oro-antral communication) with the potential of causing infection
Where do the middle ethmoidal cells open?
ethmoidal bulba
Where do posterior ethmoidal cells open?
lateral wall of superior meatus
Where does the sphenoid sinus drain?
spheno ethmoidal recess
Where do the anterior ethmoidal cells and frontal sinus drain?
infundibulum opening of frontonasal duct
