Anatomy and Physiology of The Nose Flashcards
What is the principal function of the nasal airway?
Humidify and warm inspired air
Also removes noxious particles form air and protects delicate distal lower resp. tract
What is the olfaction of the nose?
Sense organ, housing olfactory apparatus
Dysfunction can result in poor QoL
What is the role of the olfaction of the nose?
Small substances
Important role in protection from danger
Central in forming positive and negative memories
Taste - identify food flavours
Describe choanal atresia
Failed recanalization of the nasal fossae during foetal development
This is emergency as neonate will be unable to breathe
Requires surgery
What are the immune functions of the nose?
Mucus consists of compounds able to neutralise antigens
Immunoglobulin A and E
Smoking can reduce cilia and change mucus viscosity
What is the function of the nose for speech?
Nasal airflow modifies speech and produces nasal clicks or click consonants
Paranasal sinuses also contribute to vocal resonance
Describe the nasal aerodynamics as airflow enters nasal vestibule
Nasal airflow is laminar when enters nasal vestibule - no mixing of different air layers at low velocity
Describe nasal aerodynamics when in nasal valve
Is narrowest site of resp. tract
Turbulent flow with different air layers swirling together
Velocity reduces so prolonged contact with nasal mucosa
What are paranasal sinuses?
Air filled and arise from the nasal cavity
Maxilla, sphenoid, ethmoid and frontal
What are some paranasal sinus functions?
Reduce skull weight, physical buffer, vocal resonance, humidification, heat insulation, and immune barrier
Describe the external nose
Visible component
Pyramidal shape with base continuous with forehead and apex at nasal tip
What is the dorsum of the nose?
Surface between root of nose and tip
What is the opening of the nose called and what is it separated by?
Nares
Separated by columella
Describe the nasal skeleton
Bony and cartilaginous components
There is small minor cartilages and main cartilage is supported by septal cartilage
What are the types of nasal bones?
Paired, symmetrical and oblong bones
What are the main cartilages?
2 paired lateral cartilages
Upper lateral
Lower lateral - alar
Explain a nasal bone fracture
Most common facial fracture
Can result in permanent deformity
Most often surgery performed under local anaesthesia
Beware of septal haematoma
Describe saddle node deformity
Cartilage has no blood supply of own so relies on surrounding perichondrium by diffusion
Haematoma results in ischaemia and necrosis of septum
Support to nose is lost
What arteries supply the skin of external nose?
Supratrochlear and dorsal nasal arteries - branches of ophthalmic artery
Infraorbital - branch of maxillary artery
What arteries supply septum and alar cartilages?
Angular and lateral nasal artery - branch of facial artery
What is the venous drainage of external nose?
Facial vein then IJV
What is the danger triangle?
Highly anastomotic venous system of nose allows retrograde spread of infection to cavernous sinus via ophthalmic veins
Is life and sight threatening
What can the danger triangle and cavernous sinus thrombosis cause?
Ptosis, chemosis, cranial nerve palsies
Sensory defects of ophthalmic and maxillary branches
Papilledema, retinal haemorrhages and decreased visual acuity
Headache with neck stiffness
Describe the sensory innervation of the external nose
Derived from trigeminal nerve CN V
Infratrochlear and external nasal nerves for skin, nasal alae and vestibule
Infraorbital nerve for lateral aspects
Describe the motor innervation of the external nose
To nasal muscles
Facial nerve (CN VII)
Describe the nasalis muscle
Paired muscle covering dorsum of nose
Innervated by buccal branch of facial nerve
Alar part depresses and dilates nostrils
Transverse part wrinkles dorsum
Describe the procerus muscle
Small pyramidal muscle occupying glabella
Innervated by lower zygomatic or buccal of facial nerve
Depresses medial ends of eyebrows and wrinkles skin, creates facial expression of frowning
What are the 3 parts of the nasal cavity?
Vestibule - entrance lined hair bearing skin
Resp. region - ciliated pseudostratified epithelium with mucus goblet cells
Olfactory region - at apex, olfactory cells with receptors
Describe the nasal septum
Vertical wall dividing left and right nasal passages
Consists of bony and cartilaginous parts - quadrangular cartilage, vomer, perpendicular plate of ethmoid, maxillary crest and palatine bone
What are the nasal turbinate/ conchae?
3 paired bony projections from lateral nasal walls -
Superior turbinate, Middle and Inferior
These form the superior, middle and inferior meati
Why does the internal nose have rich vascular supply?
Allows humidification and warming of inspired air
Supplied from both internal and external carotid arteries
Describe epistaxis
Nosebleeds
Commonest site - Littles area (Kiesselbach plexus) on anterior septum - can control under local anaesthesia
Where does posterior bleeding come from?
Woodruff plexus - needs nasal packing
What is nasal packing?
Can be rapid rhino (inflatable) or merocel (inflates in fluid)
Foley catheter and ribbon gauze
What is the surgical management for epistaxis?
Endoscopic ligation of sphenopalatine artery
If nasal fracture then anterior ethmoid likely source so external approach
What are the paranasal sinuses lined in?
Respiratory epithelium
Describe the frontal sinuses
2 frontal sinuses
Most superior and pyramidal/ triangular in shape
What is the arterial supply, venous drainage and innervation of frontal sinus?
Arterial - anterior ethmoidal artery
Nerve - supraorbital nerve
Drainage - frontonasal duct into hiatus semilunaris
What is the arterial supply, venous drainage and innervation of sphenoid sinus?
Artery - sphenopalatine and posterior ethmoidal artery
Nerve - posterior ethmoidal nerve
Drainage - spheno-ethmoidal recess
Describe trans-sphenoidal surgery
Most often for pituitary adenoma
Avoids transcranial approach
Joint procedure with ENT and neurosurgery
What are the risks of trans-sphenoidal surgery?
Bleeding as close to internal carotid artery
CSF leaks
Describe the maxillary sinuses
Cheek sinuses
Largest of sinuses, pyramid shape and lateral to nasal cavities
What is the arterial supply, drainage and innervation of maxillary sinuses?
Artery - branches of facial and maxillary arteries
Drainage - hiatus semilunaris
Innervation - superior alveolar nerves and greater palatine nerve
Describe the ethmoid sinuses
2 ethmoidal sinuses/ group of air cells
Anterior - opens into hiatus semilunaris via ethmoid bulla
Posterior - opens into lateral wall of superior meatus
What is the arterial supply and innervation of the ethmoid sinuses?
Innervation - anterior and posterior ethmoidal branches of naso-ciliary nerve
Arterial - anterior and posterior ethmoidal arteries
Describe orbital cellulitis
Sight threatening emergency
Acute spread of infection from ethmoid or frontal sinuses
Differentiate from pre-septal cellulitis by clinical signs
What is the treatment for orbital cellulitis?
IV antibiotics
Nasal decongestants
CT scans and possible surgical drainage
Explain sinus drainage
Sphenoid - spheno-ethomoidal recess
Posterior ethmoid - lateral wall of superior meatus
Anterior ethmoid, frontal and maxillary - ostiomeatal complex in middle meatus
Where does nasolacrimal duct open into?
Inferior meatus
What is sinusitis?
Inflammation of lining of sinuses
Acute - viral
Chronic (more than 3 months) - with or without polyps
Static mucus can get infected
What are the contents nasopharynx?
Adenoids and tubal tonsils
Eustachian tube opening
What is the position of nasopharynx?
Interchangeable
Area posterior to nasal choanae, extending down to soft palate
What can enlarged adenoids or other post nasal space obstruction cause?
Obstruction of Eustachian tube
Glue ear
Unilateral in adults can be sign of nasopharyngeal mass
