L6 Nasal Cavity A

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 - Page 86 of 313 - ! 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 - Page 87 of 313 - 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 - Page 88 of 313 - 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: □ 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. - Page 89 of 313 - 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. - Page 90 of 313 - 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 - Page 91 of 313 - - Page 92 of 313 - - Page 93 of 313 - 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: □ Lateral: infratemporal fossa via pterygomaxilllary fissure □ Anterior: orbit (apex) □ Posterior: middle cranial fossa via foramen rotundum □ Medial: nasal cavity via sphenopalatine foramen - Page 94 of 313 - ! 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 - Page 95 of 313 - ! 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 - Page 96 of 313 - .

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