Sinonasal Anatomy and Physiology

21 Sinonasal Anatomy and Physiology


21.1 Nasal Septum


21.1.1 Structure


• Quadrilateral cartilage


• Perpendicular plate of the ethmoid


• Vomer


• Maxillary crest


21.1.2 Blood Supply


• Facial artery—labial branch


• Palatine artery


• Anterior ethmoid artery


• Posterior ethmoid artery


• Sphenopalatine artery—posterior septal branch


21.1.3 Innervation


• Anterior ethmoidal nerve


• Medial superior posterior nasal (inc. nasopalatine n)


21.1.4 Adjacent Structures


• Maxilla


• Nasal bones


• Upper and lower lateral cartilages


• Sphenoid sinuses


• Cribriform plate


21.2 Nasal Conchae (Turbinates) (Fig. 21.1)


21.2.1 Superior


• In continuity with MT


• Overlie the superior meatus


• Variable attachments posteriorly to the sphenoid face or lamina papyracea


• Medial surface contains olfactory epithelium



figure

Fig. 21.1 Lateral nasal wall. I, superior meatus; ii middle meatus; iii, inferior meatus. 1, nasal vestibule; 2, opening of the nasolacrimal duct; 3, origin of the inferior turbinate; 4, semilunar hiatus; 5, insertion of the middle turbinate; 6, sphenoid sinus; 7, insertion of the superior turbinate; 8, frontal sinus; a, drainage of the antral cavity; b, drainage of the frontal sinus; c, drainage of the anterior ethmoid cells; d, drainage of the posterior ethmoid cells; e, drainage of the sphenoid sinus; f, area of infundibulum (dotted area).


21.2.2 Middle


• Has four parts—anterior and posterior buttresses, vertical attachment, and basal lamella (horizontal attachment)


• Separates ethmoidal cells into anterior and posterior


• Various anomalies include pneumatization (concha bullosa) and paradoxical configurations


• Overlies the middle meatus


21.2.3 Inferior


• Largest turbinate


• Overlies inferior meatus (valve of Hassner)


21.2.4 Supreme


• May also exist in some people


21.3 Paranasal Sinuses, Ostia, and Ostiomeatal Complex


21.3.1 Embryology


• Weeks 9–10: Formation of six ridges.


• Ridges form ethmoturbinals:


figure Pars ascendens and pars descendens


figure Middle turbinate: third ethmoturbinal


figure Superior turbinate: fourth ethmoturbinal


figure Supreme turbinate: fifth ethmoturbinal


figure Inferior turbinate: maxilloturbinal


21.3.2 Messerklinger Landmarks (Fig. 21.2)


• Four consistent/constant landmarks:


figure Uncinate process


figure Ethmoid bulla: anterior wall


figure Middle turbinate basal lamella


figure Sphenoid face


• Three inconsistent landmarks:


figure Ethmoid bulla: posterior wall


figure Superior turbinate basal lamella


figure Supreme turbinate basal lamella


21.3.3 Middle Meatus


• Hiatus semilunaris:


figure H. semilunaris inferior: shortest distance between free posterior margin of uncinate process and anterior face of ethmoid bulla



figure

Fig. 21.2 Four Messerklinger landmarks. Sph, sphenoid sinus; SEC(OC), spheno-ethmoidal recess (olfactory cleft); SpM, supreme meatus; SM, superior meatus; RBR, retrobullar recess; FS, frontal sinus; ANC, agger nasi cell; EB, ethmoid bulla; Max O, maxillary ostium. 1, uncinate process; 2a, anterior wall of EB; 2b, posterior wall of EB; 3, basal lamella of middle turbinate; 3a, superior turbinate; 3b, supreme turbinate; 4, anterior face of sphenoid sinus.


figure H. semilunaris superior: crescent-shaped cleft between ethmoid bulla and middle turbinate


• Ostiomeatal complex:


figure Final common drain pathway for anterior sinuses—a functional unit


figure Includes:


– Uncinate process


– Ethmoid infundibulum


– Anterior ethmoid cells


– Ostia of anterior ethmoid, maxillary, and frontal sinuses


21.3.4 Potential Spaces


• Sinus lateralis = suprabullar and retrobullar recesses


• Suprabullar recess: space between roof of ethmoid bulla and skull base


• Retrobullar recess: space between posterior wall of ethmoid bulla and middle turbinate basal lamella


21.3.5 Uncinate Process


• Crescenteric bone that forms part of the ethmoid bone


• Free medial edge, being attached to the lateral wall of the nose—upper two-third lies in a vertical plane, lower one-third lies in a horizontal plane


• Three types of superior attachment:


figure To lamina papyracea (A) forming a recessus terminalis


figure To the skull base (B)


figure To the middle turbinate (C)


• With type A attachments, mucociliary outflow from the frontal sinus is directly into the middle meatus, in type B/C attachments, that mucociliary flow is into the ethmoid infundibulum


• “Doorway to the sinuses”


21.3.6 Maxillary Sinus


• Present at birth


• Located beneath the orbit


• Anterior to the infratemporal and pterygopalatine fossae


• Natural maxillary ostium lies at the lateral end of the ethmoid infundibulum, behind the uncinate process; accessory ostia are often seen and mistaken for the natural ostium and can lie within the lower uncinate process or posterior to the free edge of the uncinate process


• Blood supply—facial, maxillary, infra-orbital, and greater palatine arteries


• Nerve supply—infra-orbital and superior alveolar branches of maxillary nerve


21.3.7 Ethmoidal Cells


• Ethmoid bone:


figure Paired bony scaffolds, connected by cribriform plate


• Boundaries:


figure Lamina papyracea of orbit


figure Orbital process of the frontal bone


figure (Fovea ethmoidalis1 orbital plate of the frontal bone)


figure Middle and superior turbinates medially


figure Lateral cribriform plate lamella (also medially)


figure Sphenoid sinus


• Nerve supply—anterior and posterior ethmoidal nn


• Blood supply—anterior and posterior ethmoidal arteries from the ophthalmic a


• Anterior cells—drain into middle meatus


figure Agger nasi:


– Most anterior of the ethmoid cells


– Defines the anterior aspect of the frontal recess


figure Ethmoid bulla:


– Lies posterior to the uncinate process and anterior to the basal lamella


– Attached to the skull base superiorly defining the posterior end of the frontal recess and demarcating the anterior ethmoidal a


– Drains posteriorly into the retrobullar space


– Small when a pneumatized MT present


figure Infra-orbital (Haller) ethmoidal cells:


– Pneumatization along the orbital wall opposite the uncinate process—may narrow the infundibulum


figure Supraorbital ethmoid cells


– Pneumatization along the anterior skull base posterior to the frontal sinus


• Posterior cells—drain into superior meatus:


figure Between one and nine in number


figure No middle cells


figure A variant may pneumatize superior and lateral to the sphenoid sinus (sphenoethmoidal [Onodi] cell)


21.3.8 Sphenoid Sinus


• Occupies sphenoid bone


• Intersinus septum not usually midline


• Post-ethmoid a and n give vascular and sensory supplies, respectively


• Ostium ~1 cm above choana


• Main development occurs after puberty


• Relations:


figure Pituitary fossa and middle cranial fossa superiorly


figure Cavernous sinus and ICA laterally


figure Pons and posterior cranial fossa posteriorly


figure Forms roof of nasopharynx


figure Optic nerve lies next to or even within the sinus


figure Pterygoid canal with nerve inferiorly


21.3.9 Frontal Sinus


• Frontal recess:


figure Nasofrontal duct—incorrect


figure Inverted funnel shape


figure Anterior skull base is posterior boundary


figure Agger nasi cell and frontal cells may occupy space in funnel—make identification and drainage difficult


figure Anterior ethmoid artery close


• Frontal recess cells:


figure Agger nasi cell


figure Frontal cells (types I–III/IV)


figure Supraorbital ethmoid cell


figure Frontal bullar cell


figure Suprabullar cell


figure Frontal intersinus septal cell


• Occasionally absent; underdeveloped in CF patients


• Variable in size


• Bounded by anterior cranial fossa and orbits


• Start to form after age 2 years


• Blood supply = supraorbital and anterior ethmoid arteries


• Nerve supply = supraorbital nn


21.4 Sinonasal Physiology


21.4.1 True or Perceived Sinonasal Physiological Functions


• Ventilatory:


figure Humidification


figure Filtration


figure Airway


figure Buffer pressure changes


• Phonetic:


figure Voice resonance


figure Reduces bone conduction of own speech


• Immunological—humoral and cellular:


• Olfactory


• Mechanical:


figure Reduce skull weight


figure Heat insulation


21.4.2 Mucociliary Clearance (Fig. 21.3)


• Speech of particle movement = 3 to 25 mm/min at ~12 Hz


• Low levels of nitric oxide related to ciliary dysfunction


• Mucous secretions (from goblet cells) trap particulate matter, which is then propelled to nasopharynx


• Watery secretions from serous glands evaporate to moisten the inspired air


• Sinus cilial train beats towards natural ostium


• Ostial patency required for adequate mucociliary clearance and gas exchange (nitric oxide)


• Frontal sinus outflow along medial wall and into either infundibulum or middle meatus direct—depending on uncinate attachment



figure
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Jul 4, 2016 | Posted by in OTOLARYNGOLOGY | Comments Off on Sinonasal Anatomy and Physiology

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