L21: Anatomy of the Nose

Question 1

What is the function of the nose?

Answer 1

• sense of smell (olfactory receptors)
• provides route for inspired air
• filters inspired air: trapping particles in nasal hair or mucous
• moistens and warms inspired air
• resonating chamber for speech

Question 2

What is the anatomy of the nasal cavity?

Answer 2

Extends from external nose (part of nose prominent on our face) and communicates posteriorly with the nasopharynx

• inside the external nose is called the vestibule
• nostrils: anterior nasal apertures
• back of nasal cavity: posterior nasal apertures

Question 3

What is the external nose made up of?

Answer 3

Cartilage and bone (from tip to bridge)

• nasal bone
• frontal process of maxilla

Question 4

Why are the nasal bones prone to fractures?

Answer 4

Prominence of nasal bones makes them susceptible to fractures in facial injuries

Question 5

What is the function of the vestibule?

Answer 5

Filters inspired air: lined with skin containing sebaceous/sweat glands and hair

Question 6

What are the boundaries of the nasal cavity?

Answer 6

Medial wall: (nasal septum) divided into left and right halves by midline septum
Roof: nasal bone, frontal bone, ethmoid bone (cribiform plate), sphenoid bone
Lateral walls: 3 bony projections called conchae, and therefore 3 meatuses which are the spaces below each conchae

Question 7

What are the conchae formed by?

Answer 7

Underlying bones

• superior and middle conchae are part of the ethmoid bone
• inferior conchae arises from a singular bone

Question 8

Why is the lateral wall irregular?

Answer 8

Bony projections slows airflow by causing turbulence of airflow
Increases surface area over which the air passes
=humidify, warm and filter air much better

Question 9

What is found under the meatuses?

Answer 9

Openings
-allow drainage of paranasal air sinuses into the nasal cavity (most enter nasal cavity via middle meatus hole)
-naso-lacrimal duct into nasal cavity (opens into hole in inferior meatus)
=swallow

Question 10

What surgery can you do involving the nasal cavity that accesses the pituitary gland?

Answer 10

Access pituitary gland through transsphenoidal surgical approach
-through sphenoid bone

Question 11

What is the nasal septum made up of?

Answer 11

Consists of cartilaginous and bony section

• perpendicular plate of the ethmoid bone
• vomer bone
• septal cartilage

Question 12

What is a septal haematoma?

Answer 12

Complication from a nasal injury

• cartilage takes its blood supply from perichondrium
• tear blood vessels, accumulation of blood which strips the perichondrium from the underlying cartilage
• catilage can die, causing fibrosis and can effect its shape, also a site for infection and therefore development of nasal abcess

Question 13

How do you spot a septal haematoma?

Answer 13

Look up nostril
-pink swellings in vestibule
=drain and allow perichondrium to stick up against cartilage

Question 14

What is a saddle-nose deformity?

Answer 14

If you don’t treat septal haematoma

• avascular necrosis of cartilaginous septum
• affects the shape of the nose

Question 15

What is a septal deviation?

Answer 15

Caused by trauma to the nose

• displacement of septum to one side
• presents with some obstruction to airflow

Question 16

Which cranial nerve carries general sensation from the nasal cavity?

Answer 16

Trigeminal nerve (opthalmic and maxillary divisions)

Question 17

What lines the nasal cavity?

Answer 17

Respiratory mucosal membrane (very vascular): pseudostratified columnar epithelium, rich in goblet cells
Superior region of nasal cavity: olfactory mucous membrane which contains dendrites of the olfactory nerve (responds to smell)
(vestibule is lined by skin)

Question 18

What is the function of the respiratory mucous membrane?

Answer 18

• filters (mucous/cilia)
• humidifies (watery secretions)
• warms (rich blood supply)

Question 19

What are nasal polyps?

Answer 19

Fleshy, benign swellings of the nasal mucosa
-usually bilteral
-common >40 yos
-pale/yellow in appearance
Symptoms:
-blocked nose, watery rhinorrhoea
-post-nasal drip
-decreased smell and reduced taste
-more prone to developing infections of the sinuses if the holes in the meatuses are blocked= sinusitis

UNILATERAL POLYP WITH BLOOD TINGED SECRETION COULD SUGGEST A TUMOUR (not common in children, usually a forgein body)

Question 20

What is rhinitis?

Answer 20

Inflammation of the nasal mucosal lining (upper resp tract infections)

Causes:

• acute infective rhinitis: viral-common cold
• allergic rhinitis

Symptoms:

• nasal congestion (inflammation)
• rhinorrhoea
• sneezing
• nasal irritation
• postnasal drip

Question 21

What is epistaxis?

Answer 21

Nose bleed (usually Keisselbach's plexus)
-mucosa and blood vessels are easily injured (especially if dried out/trauma)

-can get bleeding from the sphenopalatine artery which is potentially more serious and more difficult to treat (can be bleeding through both nostrils)

Question 22

What is the arterial supply to the nasal mucosa/nasal cavity?

Answer 22

Arterial supply from branches of the opthalmic artery (anterior and posterior ethmoidal arteries-enter through the roof of nasal cavity), and maxillary artery (sphenopalatine artery-enters from back, greater palatine-from bottom)

Kiesselbach’s plexus: arterial anastomoses in anterior septum

• most common source of bleeding in epistaxis
• treat by pinching nose in anterior to body ridge, applying pressure to plexus
• bleeds from this plexus: come from one half of the nose

Question 23

What is the venous drainage of the nasal cavity?

Answer 23

Into the pterygoid venous plexus found within the infratemporal fossa
-connections to cavernous sinus and facial vein

Question 24

What are paranasal air sinuses?

Answer 24

Air filled spaces that are extensions of the nasal cavity
-lined with respiratory mucosa (ciliated and secretes mucus)
-reduce weight of skull
-humidify and warm air
=drain into the nasal cavity via ostia into a meatus

Infections in nasal cavity can involve sinuses (sinusitis)
-maxillary sinus is most commonly affected

Question 25

What are the different paranasal air sinuses called?

Answer 25

• frontal air sinuses (varible in people: 2-4 of them)
• ethmoidal air sinuses (air cells in ethmoid bone)
• maxillary air sinuses (one either side- maxillary teeth can project into here: dental infection can spread)
• sphenoidal air sinuses

Question 26

What are some important anatomical relations of the paranasal air sinuses?

Answer 26

• nasal cavity
• orbit (maxillary/ethmoid sinuses)
• anterior cranial fossa (frontal sinuses)

Question 27

What is the general sensory innervation to the paranasal air sinuses?

Answer 27

Branches of trigeminal

• Va (frontal, ethmoidal, sphenoid sinus)
• Vb (maxillary sinus)

Question 28

What is acute sinusitis?

Answer 28

Symptomatic inflammation of mucosal lining of nasal cavity and paranasal air sinuses
-often secondary to viral infection of nasal cavity (history of URTI)

• blocked nose and rhinorrhoea +/-green/yellow discharge
• pyrexia
• headache/facial pain (in area of affected sinus), worse on leaning forward

=self limiting condition (treatment is symptomatic), don’t treat with antibiotics

Question 29

What is the pathology of acute sinusitis?

Answer 29

-primary infection (rhinitis) leads to reduced ciliary function, oedema of nasal mucosa, and increased nasal secretions
-sinus ostia can become blocked off, so drainage from sinus is impeded
(maxillary sinus is most commonly affected, as it’s opening is high up so has to work against gravity to drain)
-stagnant secretions within the sinus become ideal breeding ground for bacteria-secondary infection
=Step.pneumoniae/H.Influenzae (secondary to viral cause of acute sinusitis)

Question 30

How do you distinguish between acute bacterial sinusitis/acute viral sinusitis?

Answer 30

Bacteria

• symptoms severe at onset
• symptoms >10 days without improvement
• symptoms that worsen after initial improvement