L17: applied anatomy of the nose, nasal cavity & sinuses

Question 1

List functions of the nose and nasal cavity

Answer 1

Sense of smell
Provides a route for inspired air
Filters inspired air – trapping particles in nasal hair or mucous
Moistens (humidifies) and warms inspired air
Resonating chamber for speech

Question 2

Describe the nasal cavity

Answer 2

Extends from the nostrils anteriorly to the posterior nasal apertures
Has a roof, floor and two walls (medial and lateral)
Floor = hard palate
Medial wall = nasal septum
Roof = frontal bone, nasal bone, cribriform plate & sphenoid bone

Question 3

Describe the external nose

Answer 3

Predominately a cartilaginous structure, but frontal processes of the maxillae and two nasal bones form its roof
As nose lies in such a prominent position – often involved in injuries to the face
Vestibule is lined with skin containing sebaceous/sweat glands and hair – filters inspired air

Question 4

Describe the lateral wall of the nasal cavity

Answer 4

Irregular due to presence of bony projections (conchae) – superior, middle & inferior
Superior & middle are part of the ethmoid bone
Meatuses – superior, middle & inferior
Slows airflow by causing turbulence of airflow & increases surface area over which air passes
Openings under the meatuses allow drainage of:
-paranasal air sinuses into nasal cavity
-nasolacrimal duct into nasal cavity

Question 5

Describe a septal haematoma

Answer 5

Potential complication from nasal injury
Cartilage of nasal septum receives blood supply from overlying perichondrium
Injury to nose can buckle septum & shears blood vessels
Blood accumulates in sub-perichondrium – depriving underlying cartilage of its blood supply

Question 6

Describe a saddle-nose deformity

Answer 6

Untreated septal haematoma leads to avascular necrosis of cartilaginous septum
ALWAYS examine for septal haematomas in patients presenting with nasal injury

Question 7

Describe the lining of the nasal cavity

Answer 7

Olfactory mucous membrane – contains dendrites of olfactory nerves (special sensory smell)
-covers over roof of nasal cavity
Respiratory mucous membrane – pseudostratified columnar ciliated epithelium rich in goblet cells
-filters (mucous/cilia)
-humidifies (watery secretions)
-warms (rich blood supply)

Question 8

Describe nasal polyps

Answer 8

Fleshy, benign swellings of nasal mucosa
Usually bilateral: common > 40 years
Symptoms: blocked nose and watery rhinorrhoea, post-nasal drip, decreased smell and reduced taste

Question 9

Describe rhinitis

Answer 9

Inflammation of the nasal mucosal lining
Many causes, lead to similar symptoms -> nasal congestion, rhinorrhoea, sneezing, nasal irritation & postnasal drip
Common causes: simple acute infective rhinitis (common cold) & allergic rhinitis

Question 10

Describe the blood supply to the nasal mucosa

Answer 10

Arterial supply from branches of ophthalmic artery and maxillary artery
-arterial anastomoses in anterior septum (Kiesselbach’s plexus)
Venous drainage from nasal cavity into pterygoid venous plexus (also drainage to cavernous sinus and facial vein)

Question 11

Describe epistaxis

Answer 11

Mucosa and blood vessels easily injured – nosebleed = epistaxis
Kiesselbach’s plexus most common source of bleeding in epistaxis – easily treatable with simple first aid measure (‘pinching nose’)
Bleeding from the sphenopalatine artery is source for a small minority of nosebleeds – potentially more serious and more difficult to treat (not easily reachable to tamponade)

Question 12

What are paranasal sinuses?

Answer 12

Air filled spaces that are extensions of the nasal cavity
Lined with respiratory mucosa & named according to bone in which they are found
Drain into the nasal cavity via small channels (ostia) into a meatus (most into middle meatus)
Infections in nasal cavity can involve sinuses (sinusitis) – maxillary sinus most commonly affected

Question 13

List the paranasal sinuses & their nerve innervation

Answer 13

Frontal
Ethmoidal
Sphenoid
Maxillary (roots of upper teeth can sometimes project in maxillary sinus) 
General sensory innervation:
Va – frontal, ethmoidal & sphenoid
Vb – maxillary

Question 14

What is acute sinusitis?

Answer 14

Symptomatic inflammation of mucosal lining of nasal cavity and paranasal air sinuses – often secondary to viral infection of nasal cavity
Clinical diagnosis: recent URTi, blocked nose and rhinorrhoea +/- green/yellow discharge, pyrexia & headache/facial pain which is worse on leaning forward
Self-limiting: treatment is symptomatic

Question 15

Describe the pathophysiology of acute sinusitis

Answer 15

Primary infection leads to reduced ciliary function, oedema of nasal mucosa, sinus ostia & increased nasal secretions
Drainage from sinus is impeded (maxillary is the most affected)
Stagnant secretions within the sinus – ideal breeding ground for bacterial infection (strep pneumoniae, haemophilus influenzae & moraxella catarrhalis)

Question 16

When is acute bacterial sinusitis more likely?

Answer 16

Symptoms particularly severe at onset
Symptoms > 10 days without improvement
Symptoms that worsen after an initial improvement (suggesting secondary bacterial infection)