L6 A. Nasal Cavity ! Nose divided into right and left nasal cavities by □ Considered part of upper respiratory tract □ Lower respiratory tract includes larynx, trachea, bronchi, bronchioles and alveoli ! Openings of nose: anterior and posterior nares ! 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 1. Bony Framework of Nasal Cavity ! Nose: immovable bony bridge supported by □ Nasal □ Nasal part of frontal bone □ Frontal of ! Medial wall: nasal septum □ Septal cartilage □ □ Perpendicular plate of ! Roof: □ Frontal bone □ □ Cribriform plate of ethmoid bone □ Sphenoid bone

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! Floor: □ Palatine process of maxilla □ Horizontal plate of ! Lateral wall: □ Mainly formed by three conchae (turbinates): → Superior → → Inferior nasal concha □ Divides lateral part of nasal cavity into four potential spaces: → Spheno-ethmoidal recess above → 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 → → 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

□ 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 □ 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: □ 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 □ Can be due to infection or allergy □ Infections of nasal cavities may spread to: → Anterior cranial fossa → Middle ear through auditory tube → Paranasal sinuses → 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 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 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: □ □ Ethmoidal 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: 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: □ 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 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 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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