Session 7: Applied Anatomy of the Nose, Nasal Cavity and Paranasal Sinuses Flashcards
Functions of nose and nasal cavity.
Sense of smell
Provides a route for inspired air
Filters inspired air by trapping particles in nasal hair and mucous.
Moistens, humidifies and warms inspired air.
Resonating chamber for speech
Allows drainage of secretions from paranasal sinuses and nasolacrimal ducts.
What can the nose be divided into?
External nose, nasal cavity and nasopharynx.
What are the two parts of the external nose?
Cartilaginous part
Bony part
What forms the root of the external root?
The frontal processes of the maxillae and two nasal bones.
What injuries are the nose susceptible to?
Septal haematomas
Septal deviations
Nasal bone fractures
Explain the gross structure of the nasal cavity.
It extends from the nostrils anteriorly known as the anterior nasal apertures to the posterior nasal apertures which are also known as choanae.
It also has a roof, a floor, and two walls lateral and medial.
What is the medial wall of the nasal cavity formed by?
Consist of a bony and cartilaginous part.
Formed by the nasal septum.
What does the nasal septum consist of?
The perpendicular plate of the ethmoid bone, septal cartilage, vomer.
What does the cartilaginous part of the septum rely on for its blood supply?
The overlying perichondrium
Where does inspired air first enter the nose?
The vestibule
What is the vestibule lined with?
Skin containing sebaceous/sweat glands and hair.
It’s keratinised stratified squamous epithelium.
What does the nasal cavity communicate with posteriorly?
The nasopharynx
How can the lateral wall of the nasal cavity be described?
Irregular
What makes the lateral wall of the nasal cavity irregular?
Bony projections also known as conchae.
State the conchae of the nasal cavity.
Superior
Middle
Inferior
What are the superior and middle conchae made of?
They are part of the ethmoid bone.
What is the inferior conchae made of?
It is a bone on its own.
What are found between the conchae?
The superior, middle and inferior meatuses of the nasal cavity.
What are the functions of the conchae and meatuses of the nasal cavity?
Slows airflow by causing turbulence of airflow.
Increases surface area of which air passes.
The paranasal air sinuses and orbit communicate with the nasal cavity through openings in the lateral wall. There are openings under the meatuses that allow for drainage.
Explain what happens in a septal haematoma.
Usually due to blunt trauma to the nose. The perichondrium is stripped off the cartilaginous part of the nasal septum. Blood collects between those parts called sub-perichondrial haematoma of the septum.
Complications of septal haematoma.
The septal cartilage relies on the perichondrium for its blood supply. If there is a septal haematoma the cartilage doesn’t get its blood supply. This leads to ischaemia of the cartilage.
If the septal haematoma is not recognised and not treated it can lead to irreversible necrosis and what is called a saddle-nose deformity.
Another thing that can develop is infection in the collecting haematoma which can lead to a septal abscess. This further increases likelihood of avascular necrosis and saddle deformity.
Which cranial nerve carries general sensation from the nasal cavity?
Trigeminal nerve
What nerve makes a snotty and runny nose?
The facial nerve
What is the nasal cavity lined with?
Mucous membrane that is highly vascular
What types of mucous membrane is the nasal cavity lined with?
Olfactory mucous membrane
Respiratory mucous membrane
What can be found in the olfactory mucous membrane?
It houses olfactory receptor neurones for smell
What can be found in the respiratory mucous membrane?
Pseudostratified columnar epithelium rich in goblet cells.
Functions of the respiratory mucous membrane.
Filters air via the mucous and cilia
Humidifies air
Warms the air
What are nasal polyps?
Fleshy benign swellings of the nasal mucosa.
They are usually bilateral.
Which age group are nasal polyps most common in?
>40 years of age
Appearance of nasal polyps.
Pale or yellow in apeparance. They can also appear fleshy and reddened.
Symptoms of nasal polyps.
Blocked nose and water rhinorrhoea.
Post-nasal drippage
Decreased sense of smell and taste
What’s the difference between bilateral and unilateral nasal polyps?
Unilateral nasal polyps are far more concerning. They may release blood-tinged secretion and can suggest a tumour growth and malignancy.
What is rhinitis?
Inflammation of the nasal mucosal lining
Symptoms of rhinitis.
Nasal congestion
Rhinorrhoea
Sneezing
Nasal irritation
Post-nasal drip
Common causes of rhinitis.
Simple acute infective rhinits (viral)
Allergic rhinitis like pollen allergy.
The symptoms are more or less the same.
6 yr old present with 1 week history of a runny nose. His mum nothes that this discharge is only coming from one nostril (left). Over the last few days the discharge has become smelly and blood stained. He is otherwise well.
What is the likely diagnosis? Explain.
A - Infective rhinitis
B - Nasal cancer
C - Foreign body
D - Allergic rhinitis
E - Nasal polyp
Foreign body.
It is not infective rhinitis is that is usually bilateral rhinorrhoea and usually not blood stained.
Nasal cancer is not common in children.
Nasal polyps are usually bilateral and not common in children.
Allergic rhinitis is usually bilateral and also doesn’t produce a smelly and blood stained discharge.
What is epistaxis?
Nose bleed
What is the arterial supply of the nose?
Via branches of the ophthalmic artery and the maxillary artery.
There are arterial anastomoses in the anterior septum.
What are the arterial anastomoses in the anterior septum collectively called?
Kiesselbach’s plexus
Clinical significance of the kiesselbach’s plexus.
The most common source of bleeding in epistaxis.
How to treat epistaxis.
Pinching nose and tilting head forward
What are the arteries called arising from the ophthalmic artery?
Anterior and posterior ethmoid
What are the arteries that arise from the maxillary artery that supply the nasal cavity called?
Sphenopalatine artery
The greater palatine artery.
Explain the venous drainage of the nasal cavity.
Into the pterygoid venous plexus which also drain to the cavernous sinus and the facial vein.
It is however not common for pathogens to drain into cavernous sinus and cause intracranial infection via this route.
What is special about bleeding from the sphenopalatine artery?
More serious and more difficult to treat as it is not easily reachable to tamponade
What are the four paranasal sinuses?
Maxillary
Frontal
Ethmoidal
Sphenoidal
They are all paired except for the sphenoid air sinus.
What are the paranasal sinuses filled with?
They are air filled spaces which are extensions of the nasal cavity.
What are the paranasal sinuses lined with?
Respiratory mucosa.
Functions of the paranasal sinuses.
Humidify and warm inspired air. They also reduce the weight of the skull.
The paranasal sinuses are ciliated and secrete mucous. What do they drain into?
They are drain into the nasal cavity via small channels called ostia.
Most of them drain into the middle meatus.
Which is the largest paranasal sinus?
The maxillary sinus.
What do the ethmoidal paranasal sinuses consist of?
Anterior, middle and posterior air cells.
General sensory innervation of the paranasal sinuses.
Frontal, ethmoidal and sphenoid from CN Va
Maxillary from CN Vb
What is acute sinusitis?
Symptomatic inflammation of mucosal lining of the nasal cavity and paranasal air sinuses.
Which paranasal sinus is most commonly affected by acute sinusitis?
Maxillary sinus
Signs and symptoms of acute sinusitis.
Blocked nose
Rhinorrhoea which may be green or yellow.
Pyrexia
Headache and facial pain by the affected paranasal sinus/es.
Tooth ache.
The symtpoms typically peak early but resolve gradually
Why might you get a tooth ache due to acute sinusitis?
What does that tell you about which sinus is affected?
The roots of the upper teeth can sometimes project in the maxillary sinus. Inflammation of the maxillary sinus can therefore lead to a tooth ache of upper teeth.
Causes of acute sinusitis.
Infections of the nose (upper respiratory tract infections) and dental infections.
Most commonly secondary to viral infections of the nasal cavity.
Explain the pathophysiology of acute sinusitis.
The primary infection like rhinitis leads to reduced ciliary function, oedema and increased mucosal secretions.
The drainage from the sinus may become obstructed if the oedema involves the openings into the nasal cavity (sinus ostia).
The stagnant secretions within the sinus become ideal breeding ground for bacteria to cause a secondary infection.
How can one distinguish between acute sinusitis and acute bacterial sinusitis.
The acute bacterial sinusitis symptoms are particularly severe at onset and symptoms may last more than 10 days without improvement.
Symptoms may also worsen after the initial improvement.
All of this suggests that the sinusitis may be baceterial.
Most common bacteria causing acute bacterial sinusitis.
Streptococcus pneumoniae
Haemophilus influenzae
Moraxella catarrhalis
Why is the maxillary sinus particularly prone to acute sinusitis?
Because its location where the opening is high on the wall of the nasal cavity. It is most likely to become blocked because of this.
Treatment of acute sinusitis.
Treat symptoms with analgesics, antipyretics and steam inhalation.
Antibiotics if bacterial
Complications of acute sinusitis.
Rare but may occur. Depends on which sinuses are involved.
Ethmoidal sinuses may break through the thin medial wall of the orbit and spread infection into the orbit. This can cause orbital cellulitis which can be potentially sight threatening. May involve the optic nerve and can also cause intracranial infection.
