Anatomy of the nose, nasal cavities and paranasal sinuses Flashcards
What structures make up the external nose?
Cartilage and Bone (nasal bone and maxilla)
What is the vestibule of the external nose lined with?
- Skin containing sebaceous / sweat glands
- Hair
What are the boundaries of the nasal cavity?
Roof: Cribiform palate
Floor: Hard Palate
Medial wall: nasal septum
What are the projections that come out of the lateral wall of the nasal cavity and what is their function?
Projections = bony conchae (Superior, Middle and Inferior)
Meatus= spaces between projections
Function: Slows airflow by causing turbulent airflow
Increases surface area over which air passes
What lines the lateral wall of the nasal cavity?
Respiratory epthelium
Why does your nose run when crying?
Tears from the lacrimal gland spill into the nasal cavity
Which meatus of the nasal cavity do the paranasal air sinuses open into?
Middle Meatus
What components make up the nasal septum?
A bony and cartilaginous part:
Bone: Vomer bone and Perpendicular plate (of ethmoid bone)
Cartilage: Septal cartilage
Where does the nasal cartilage recieve its blood supply from?
How can this be problematic in injury to the nose?
Nasal cartilage recieves blood supply from overlying perichondrium
Injury to nose can buckle the septum, shearing blood vessels →blood accumulates in subperichondrium →septal haematoma → underlying cartilage deprived of blood supply
How would you treat a septal haematoma?
By tamponade
Drain the haematoma and apply cotton wool forcing the perichondrium back onto cartilage
What is the consequence of an untreated sepatal haematoma and why does this happen?
Saddle Nose Deformity
Untreated haematoma causes avascular necrosis of septal cartilage
Haematoma is also a site for infection which further increases changes of avascular necrosis
Which cranial nerve carries general sesnation from the nasal cavity?
Trigeminal (Maxillary Vb branch)
The nasal cavity is lined with 2 mucus membranes, describe the 2 membranes and the function of each
- Olfactory mucus membrane - houses Olfactory receptor neurones for sense of smell (CN1)
-
Respiratory mucus membrane - pseudostratified columnar ciliate epithelium, rich in goblet cells
- filters air (mucus and cilia)
- Humidifies air (watery secretions)
- Warms air (rich blood supply)
What are nasal polyps and what do they look like?
Fleshy, benign swellings of nasal mucosa
Can be pale or yellow and are fleshy in appearance (can be reddened)
Are nasal polys usually bilateral or unilateral?
Bilateral
If unilateral and blood tinged this is more concerning - may suggest a tumour
What symptoms do you get with a nasal polyp?
- Blocked nose
- watery rhinorrhoea
- Post nasal drip (down the back of the throat)
- Decreased smell and reduced taste
What is rhinitis and what are the main symptoms?
Inflammation of the nasal mucosal lining
Symptoms:
- nasal congestion
- Rhinorrhoea
- Sneezing
- Nasal Irritation
- Postnasal drip
What are the common causes of rhinitis?
- simple acute infective- viral
- allergic
What is epistaxis?
Nose bleed
Why is the nose so vascular?
To allow for warming and humidification of inspired air
Which arteries supply the nasal cavity?
What is the most common source for bleeding in epistaxis?
Branches of opthalmic and maxillary arteries
Anastamoses in the anterior septum form Kiesselbach’s plexus (or Little’s area)- the main site for nose bleeds
What is the the venous drainage of the nasal cavity?
Pterygoid venous plexus
(also drains to cavernous sinus and facial vein)
Bleeding from which artery in the nose is not easily treatable by first aid and may require surgery to ligate?
Bleeding from Spehnopalatine artery (a branch of maxillary)
At the posterior of the nasal cavity so cannot be reached by tamponade
What are paranasal air sinuses and what is their function?
Air filled spaces that are extensions of the nasal cavity
Function: humidify and warm inspired air and help reduce weight of skull
Which type of mucusa lines paranasal sinuses?
respiratory mucosa
How do paranasal sinuses drain into the nasal cavity?
Drain by a small channel called ostia into a meatus (most commonly middle meatus)
Identify the paranasal air sinuses
Which nerves recieve general sensory innervation from the paranasal air sinuses?
Frontal, ethmoid and sphenoid → Trigeminal Opthalmic division (Va)
Maxillary → Trigeminal Maxillary division (Vb)
What is acute sinusitis?
Symptomatic inflammation of mucosal lining of the nasal cavity and paranasal air sinuses
Often secondary to a viral infection of the nsal cavity
What are some of the symptoms of acute sinusitis?
- Recent URTI
- Blocked nose and rhinorrhoea +/- green/ yellow discharge
- Pyrexia
- Headache / facial pain worse on leaning forwards
How do you treat acute sinutisis?
Mostly self limiting
Use analgesics, antipyretics and steam inhalation to treat symptoms
Explain why a primary infection can lead to acute sinusitis?
- Primary infection causes reduced ciliary function, increased nasal secretions and oedema of nasal mucosa
- Therefore drainage from the nasal sinuses is impeded
- Stagnant secretions allow bacterial growth for a second infection
Which bacteria most commonly cause acute bacterial sinusitis?
- Streptococcus pneumonia
- Haemophilus Influenzae
- Moraxella Catarhalis
Why is the maxillary sinus the most commonly affected paranasal air sinus?
It’s ostia is located high on the wall of the nasal cavity therefore drainage from the sinus is harder
Why is a rare, but serious consequence of ethmoidal sinus infection, sight threatening?
- Infection in air cells of ethmoid sinus can break through the thin, medial wall of the orbit
- Infection can spread to the orbit causing orbital cellulitis
- Infection sight threatening as it may involve the optic nerve or track back to involve intracranial structures
What is a serious, but rare intracranial complication of sinutsitis? Explain how with reference to the anatomy of venous drainage of the sinuses
Cavernouse Sinus Thrombosis
- Secondary from infection spreading from the nose through the anastamosis of venous dranage from nasal mucosa/ sinuses to cavernous sinus
What structures can be affected as a result of cavernous sinus thrombosis?
Any structure running through the cavernous sinus:
- Occulomotor nerve
- Abduscens nerve
- Trochlear nerve
- Opthalmic division of the trigeminal
- Maxillary Division of the trigeminal
- Internal Carotid
- Sympathetic plexus surrounding the carotid artery
