S9) Functional Anatomy of the Nose, Nasal Cavity and Paranasal Sinuses Flashcards
Describe the anatomical location of the nasal cavity
The nasal cavity extends from the anterior nasal aperture (nostrils) to the posterior nasal aperture (choanae)
Identify 5 functions of the nose and nasal cavity
- Sense of smell
- Route for inspired air
- Filters inspired air (nasal hair/mucous)
- Moistens and warms inspired air
- Resonating chamber for speech
Identify and describe the two components of the external nose
- Bony component – nasal bone and frontal process of maxilla
- Cartilaginous component – two lateral cartilages, two alar cartilages and one septal cartilage
What is the most commonly fractured bone of the facial skeleton?
Nasal bone (due to prominence)
How does inspired air enter the nasal cavity?
Inspired air enters via the vestibule which is the area surrounding the anterior external opening to the nasal cavity
What lines the surface of the vestibule (of the external nose)?
- Skin
- Hairs
What sort of membrane lines the nasal cavity?
Olfactory and respiratory mucous membranes
What sort of epithelium is found in the respiratory mucous membrane?
Pseudostratified columnar ciliated epithelium
What are the actions of the respiratory mucosa?
- Filters (mucous/cilia)
- Humidifies (watery secretions)
- Warms (rich blood supply)
Which structures drain into the nasal cavity?
- Paranasal sinuses
- Nasolacrimal duct (drains eye)
What are the different boundaries of the nasal cavity?
Which structures forms the floor of the nasal cavity?
The hard palate
Describe the structure of the lateral wall of the nasal cavity
Bony projections — inferior conchae, middle conchae, superior conchae
Explain how the structure of the lateral wall of the nasal cavity is adapted to its functions
- Slows airflow by causing turbulence of airflow
- Increases surface area over which air passes
Which physical features of the nasal cavity allow for the slowing of inspired air?
- Movement from narrow vestibule to large nasal cavity
- Conchae offer more resistance and disturbs the laminar flow of air
Which three structures form the roof of the nasal cavity?
Which two structures form the medial wall of the nasal cavity?
Describe the blood supply of the cartilaginous part of the nasal septum
Cartilaginous part of septum takes blood supply from overlying perichondrium
Why should one always examine for septal haematomas in patients presenting with nasal injury?
- Trauma to nose can buckle the septum and shear blood vessels
- Blood accumulates between perichondrium and cartilage
What is a saddle nose deformity?
A saddle nose deformity is a condition due to an untreated septal haematoma which leads to avascular necrosis of cartilaginous septum
Besides saddle nose deformity, what is another complication of untreated septal haematoma?
An infection in the collecting haematoma can develop and the septal abscess formation further increases likelihood of avascular necrosis of septum
Which cranial nerve carries general sensation from the nasal cavity?
Trigeminal nerve
What are nasal polyps?
- Nasal polyps are fleshy, benign swellings of nasal mucosa which are usually pale/yellow and reddened
- They are usually bilateral and are common >40 years
Identify 5 symptoms of nasal polyps
- Blocked nose
- Watery rhinorrhoea
- Post-nasal drip
- Decreased smell
- Reduced taste
What is rhinitis?
Rhinitis is the inflammation of the nasal mucosal lining
Identify 5 symptoms of rhinitis
- Nasal congestion
- Rhinorrhoea (“runny” nose)
- Sneezing
- Nasal irritation
- Postnasal drip
Identify two of the commonest causes of rhinitis
- Simple acute infective rhinitis (common cold)
- Allergic rhinitis
Nasal mucosa and blood vessels easily injured.
What is the result?
Epistaxis (nosebleed)
Describe the arterial supply of the nasal cavity
- Anterior & posterior ethmoidal arteries (branch of ophthalmic artery)
- Sphenopalatine artery (branch of maxillary artery)
What is Kiesselbach’s plexus?
Kiesselbach’s plexus (Little’s area) is an area of arterial anastomoses in the anterior nasal septum (most common source of bleeding in epistaxis)
Describe the venous drainage of the nasal cavity
Venous drainage into pterygoid venous plexus, cavernous sinus and facial vein
What is significant about bleeding from the sphenopalatine artery in the nasal cavity?
- Bleeding from the sphenopalatine artery is source for small minority of nosebleeds
- It is potentially more serious and difficult to treat (posterior & high pressure)
What are the paranasal sinuses?
The paranasal sinuses are air filled spaces that are extensions of nasal cavity (rudimentary/absent at birth)
Identify the 4 different paranasal sinuses
Describe the structure and function of the paranasal sinuses
- Structure: lined with respiratory mucosa (ciliated)
- Function: secrete mucous, help humidify and warm inspired air, reduce weight of the skull
Describe the drainage of the paranasal sinuses
All drain into the nasal cavity via small channels called ostia into a meatus (mostly middle meatus)
Identify the important anatomical relations of the paranasal sinus
- Nasal cavity
- Orbit
- Anterior cranial fossa
Describe the specific sensory innervation to the different paranasal sinuses
- Frontal, ethmoidal and sphenoid sinuses ⇒ CN Va
- Maxillary sinus ⇒ CN Vb
In the X-ray below, label the following:
- Frontal sinuses
- Orbit
- Ethmoid air cells
- Nasal cavity
- Floor of orbit
In the X-ray below, label the following:
- Maxillary sinuses
- Zygoma
- Zygomatic process
- Mandible
In the diagram below, identify the four paranasal sinuses
Which sinuses are visible lying in close proximity to the medial wall of the orbits?
Infections in nasal cavity can involve sinuses (sinusitis).
Which is the most commonly affected paranasal sinus?
Maxillary sinus most commonly affected
What is acute sinusitis?
Acute sinusitis is the acute inflammation of the lining of the sinus which is commonly infective and often secondary to the viral infection of nasal cavity (common cold)
Identify 5 signs and symptoms of acute sinusitis
- Non-resolving cold
- Pyrexia
- Blocked nose
- Rhinorrhoea (± green/yellow discharge)
- Headache/facial pain (area of affected sinus)
Why might a patient with sinusitis complain of toothache?
- Roots of upper teeth can sometimes project into maxillary sinus
- Pain in the maxilla/maxillary sinus can radiate to oral cavity
Outline the pathophysiology of acute sinusitis
- Primary infection e.g. rhinitis leads to reduced ciliary function, oedema of nasal mucosa and sinus ostia and increased nasal secretions
- Drainage from sinus is impeded and secondary bacteria breed in stagnant secretions
Identify some important anatomical relations of the nasal cavity
- Paranasal sinus
- Sphenoid bone
- Orbit
- Nasopharynx
- Oral cavity
What is epistaxis?
Epistaxis is the common occurrence of bleeding from the nose
What are some causes for epistaxis?
- Occur spontaneously
- Very minor trauma
- Abnormal coagulation
- Connective tissue disorders
Which groups of patients commonly present with epistaxis?
- Very young (2-10 years)
- Old (> 50-60 years)
Outline the 6 steps in the management of epistaxis
⇒ Apply simple compression (cartilage)
⇒ Lean forward
⇒ Cauterisation
⇒ Anterior packing with nasal tampons
⇒ Posterior packing with nasal tampons
⇒ Surgical intervention e.g. embolisation, ligation of blood vessels
