L6 Nasal Cavity
A. Nasal Cavity
! Nose divided into right and left nasal cavities by nasal septum
□ Considered part of upper respiratory tract
□ Lower respiratory tract includes larynx, trachea, bronchi, bronchioles
and alveoli
! Openings of nose: anterior and posterior nares
! Pharynx separates upper and lower respiratory tracts
□ Nasopharynx posterior to posterior
nares
□ Oropharynx behind to oral cavity
□ Laryngopharynx posterior to larynx
! Functions of nasal cavity:
□ Respiration
□ Olfaction (smelling)
□ Filtration of dust
□ Humidification of air
□
Drainage of paranasal sinuses
1. Bony Framework of Nasal Cavity
! Nose: immovable bony bridge supported by
□ Nasal bone
□ Nasal part of frontal bone
□ Frontal process of maxilla
! Medial wall: nasal septum
□
□
□
Septal cartilage
Vomer
Perpendicular plate of
ethmoid bone
! Roof:
□
□
□
□
Frontal bone
Nasal bone
Cribriform plate of
ethmoid bone
Sphenoid bone
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! Floor: hard palate
□ Palatine process of maxilla
□ Horizontal plate of palatine bone
! Lateral wall:
□
□
Mainly formed by three conchae
(turbinates):
→ Superior nasal concha
→ Middle nasal concha
→ Inferior nasal concha
Divides lateral part of nasal cavity into
four potential spaces:
→ Spheno-ethmoidal recess above
superior nasal concha
→ Superior meatus below superior
concha
→ Middle meatus below middle
concha
□
□
□
→ Inferior meatus below inferior
concha
Superior and middle conchae formed
by ethmoidal bone
Inferior concha is a separate bone
Other parts of lateral wall formed by:
→ Maxilla
→ Lacrimal bone
→ Palatine bone
→ Medial pterygoid plate of sphenoid bone
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2. Lining and Sensory Innervation of Nasal Cavity
! Majority: pseudostratified ciliated epithelium
□ Includes nasal cavity and paranasal sinuses
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□
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Anterior 1/2: anterior ethmoidal n. (from V1)
Posterior 1/2: from V2 via pterygopalatine ganglion
→ Septal wall: nasopalatine n. (after crossing nasal roof)
→ Lateral wall: nasal branches of pterygopalatine ganglion
General sensory supply from V1 and V2
□ Parasympathetic secretomotor supply from greater petrosal n. (VII)
! Near roof: olfactory epithelium
□ Contains cell body from olfactory n. (CN I)
□ Conveys smell to brain
□
Anosmia: loss of sense of smell
→ Occurs gradually with age
→ Olfactory cells degenerate at rate ~1%/y in most elderly persons
→ Other causes: conditions affecting olfactory receptors, bulb or tract in
intracranial region
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3. Blood Supply of Nasal Cavity
! Supplied by branches of:
□ Maxillary a. (ECA)
□ Facial a. (ECA)
□ Ophthalmic a. (ICA)
! Branches of maxillary a.:
□ Sphenopalatine a. from
sphenopalatine foramen
□ Greater palatine a.
! Branches of facial a.:
□ Septal branch of superior
□
labial a.
Alar branch of lateral
nasal a.
! Branches of ophthalmic a.:
□ Anterior ethmoidal a.
□ Posterior ethmoidal a.
! Venous drainage:
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□
□
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Superior: ophthalmic v.
Lateral: infraorbital v.
Superficial: facial v.
Posterolaterally: pterygoid
plexus
! Epistaxis (nosebleed)
□ Common condition due to
rich blood supply
□ Usually caused by trauma, infection and hypertension
*Note that venous drainage retains the pattern of arterial supply. 2nd and 3rd parts of maxillary a. is
replaced by the pterygoid plexus in infratemporal region in venous drainage. Its terminal branch
infra-orbital a. becomes infra-orbital v., which also drains into pterygoid plexus.
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4. Clinical Relevance
! Rhinitis: inflammation of nasal mucosa
□ Can be due to infection or allergy
□ Infections of nasal cavities may spread to:
→ Anterior cranial fossa
→ Middle ear through auditory tube
→ Paranasal sinuses
→ Lacrimal apparatus and conjunctiva
! Fracture of the nose:
□ Commonly result from trauma
□ Extension of fracture above
→ affects cribriform plate of ethmoid bone + tear meninges
→ CSF rhinorrhea due to CSF leakage into nasal cavity
! Nasal septal deviation: deviation of septum from midline
□ Can be due to:
→ Birth injury
→ Congenital malformation
→ Postnatal trauma
□ Severe → obstruct breathing → require surgery
! Le Fort classification of facial fractures:
□ Used to classify fractures of midface
□ Involves separation of all or a portion of
midface from skull base
□
Involves separation of maxilla from
□
pterygoid plates
Types:
→ Le Fort type 1: floating palate
→ Le Fort type 2: floating maxilla
→ Le Fort type 3: floating face
*Note that the ethmoidal cells forming the medial wall of orbit is the most vulnerable
part of orbit. It is prone to fractures.
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B. Paranasal Sinuses
! Paranasal sinuses:
air-filled extensions of nasal cavity
! Includes:
□ Frontal sinus
□ Ethmoidal sinus
□ Sphenoid sinus
□ Maxillary sinus
! Function: not well-defined
□ Add resonance to voice
! Drainage:
! Hiatus semilunaris provides drainage to
maxillary sinus
□ Inferiorly bound by the sharp concave
margin of uncinate process of
ethmoid
□
Leads into infundibulum of
frontonasal canal
→ Superiorly bound by ethmoidal
bulla
→ Inferiorly bound by lateral
surface of uncinate process
! Note that the opening of maxillary sinus is above its floor
□ Secretions more likely to be retained → drainage affected
□ Accounts for the most commonly infected sinus
□ Can be drained by lying face down and tilt head by 35o
! Blood supply:
□ Branches of ophthalmic artery (from ICA)
□ Branches of maxillary artery (from ECA)
□ NO contribution by facial a.
! Innervation: V1 and V2
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C. Pterygopalatine Fossa
! Pterygopalatine fossa: a small space found
below orbit
! Relations:
□
Lateral: opens into intratemporal fossa
via pterygomaxillary fissure
□ Anterior: maxilla
□ Posterior: pterygoid process of sphenoid
bone
□ Medial: palatine bone
□ Roof: greater wing of sphenoid (incomplete)
□ Floor: palatine bone
! Communications:
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□
□
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Lateral: infratemporal fossa via pterygomaxilllary fissure
Anterior: orbit (apex)
Posterior: middle cranial fossa via foramen rotundum
Medial: nasal cavity via sphenopalatine foramen
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! Contents:
□
Maxillary nerve (CN V2) – most important
□
□
Maxillary artery
Pterygopalatine ganglion
! Maxillary nerve enters pterygopalatine fossa via foramen rotundum in
sphenoid bone and gives the following branches:
□
□
Meningeal branch (arises inside cranium)
Zygomatic branch leaving via inferior orbital
fissure
□
Ganglionic branches (pterygopalatine
nerves): two short nerves to pterygopalatine
□
ganglion
Superior alveolar nerves to gum, cheek, upper
teeth and maxillary sinus
→ Ant., mid. and post. superior alveolar nn.
! Terminal branch exits orbit via infra-orbital canal
to face as infraorbital nerve
! Zygomatic branch:
□ Enters canals inside zygomatic bone to form zygomaticotemporal and
zygomaticofacial nerves to supply skin of face on temple and cheek
□ Zygomaticotemporal nerve carries parasympathetic fibres (from CN VII)
superiorly to join lacrimal n. (V1) to provide innervation for lacrimal gland
! Ganglionic branches contain:
□ Descending sensory fibres from CN V2 to nose, palate and pharynx
□ Ascending parasympathetic fibres from CN VII (via ganglion) to lacrimal
gland
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! Pterygopalatine ganglion: parasympathetic ganglion
□ Function: secretomotor control of lacrimal and nasal glands
! Branches of pterygopalatine ganglion:
□
Orbital branches: enter orbit through
inferior orbital fissure
→ Parasympathetic GVE (CN VII)
to lacrimal gland
□
Greater and lesser palatine nerves to
greater and lesser palatine canal
→ GSA (CN V2) to palate, tonsil
and nasal cavity
□
Nasal branches: lateral wall of nasal
cavity
→ GSA (CN V2) to nasal cavity
□
Pharyngeal branches: posteriorly
→ GSA (CN V2) to roof of
nasopharynx
□
Nasopalatine branch across roof of
nasal cavity to septum then descends through incisive foramen in palatine
process of maxilla to roof of mouth
→ GSA (CN V2) to nasal septum and anterior part of roof of mouth
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