ANAT P.11 - The Nose and Paranasal Sinuses PDF

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ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 Functions: OUTLINE ○ Respiratory passage: conduit for inspired air and expired air; warming, air-conditioning, humidifying, and filtering I. THE NOSE...............................................................1 ○ Protective function: mucociliary clearance, immunologic defense (IgA) A. FUNCTIONS...........................................................1 ○ Vocal resonance/phonation/speech II. THE EXTERNAL NOSE AND VESTIBULE........... 1 ○ Nasal reflex function A. NASAL BONE.........................................................1 ○ Olfaction B. UPPER AND LOWER LATERAL CARTILAGES.... 1 II. THE EXTERNAL NOSE AND VESTIBULE C. VESTIBULE AND SKIN..........................................2 A. NASAL BONE III. MUSCLES..............................................................2 Most commonly fractured bone in the human body A. PROCERUS........................................................... 2 Paired rectangular bone in the upper nasal dorsum B. NASALIS.................................................................2 Bounded by the: ○ Frontal bone: superiorly IV. BLOOD SUPPLY................................................... 2 ○ Medial portion of other nasal bone: medially V. NERVE SUPPLY.....................................................2 ○ Upper lateral cartilages: inferiorly VI. LYMPHATIC DRAINAGE...................................... 2 ○ Maxilla: laterally VII. NASAL SEPTUM................................................. 3 Forms shape of external nose Ossifies at 3rd intrauterine month A. OSTEOLOGY......................................................... 3 B. BLOOD SUPPLY.................................................... 3 C. NERVE SUPPLY.................................................... 4 D. LYMPHATIC DRAINAGE........................................4 VIII. LATERAL WALL OF THE INTRANASAL CAVITY....................................................................... 4 A. LATERAL WALL..................................................... 4 B. INFERIOR MEATUS...............................................5 C. INFERIOR TURBINATE......................................... 5 D. MIDDLE MEATUS.................................................. 5 E. MIDDLE TURBINATE............................................. 5 F. SUPERIOR MEATUS AND TURBINATE................ 6 G. BLOOD SUPPLY....................................................6 H. NERVE SUPPLY.................................................... 6 I. LYMPHATIC DRAINAGE......................................... 6 Figure 1. Anterior View of the Left Nasal Bone IX. PARANASAL SINUS............................................ 6 B. UPPER AND LOWER LATERAL CARTILAGES A. MAXILLARY BONE AND SINUS............................7 B. ETHMOID BONE AND SINUS............................... 8 C. SPHENOID BONE AND SINUS............................. 9 D. FRONTAL BONE AND SINUS............................. 10 CHECKPOINT...........................................................11 References............................................................... 11 I. THE NOSE A. FUNCTIONS Consists of the external nose and nasal cavity, both divided into right and left halves by the septum. Figure 2. Upper and Lower Lateral Cartilages GUINANGHAN, LABUGUEN, PAGUINTO Page 1 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 Plastic surgeons refer to this as “upper or lower lats” Pyramid slip of muscle deep in the superior orbital nerve, Composed of hyaline cartilage artery, and vein Prevent collapse of the vestibule Function: Form the mid and lower third of the nose ○ Shortens the nose Lower lateral cartilage a.k.a. Alar cartilage ○ Lowers the skin between eyebrows ○ Gives the external nose its form and shape ○ Aids in the expression of anger ○ Provides stability to the vestibule (a.k.a. nostril) Origin: Arises from fascia (lower part of the nasal bone and ○ Determine the appearance of the nasal tip and upper part of the cartilages) the shape of the nares Insertion: ○ Caucasian nose looks narrow due to pointed alar ○ Skin between the two eyebrows cartilage and Asian nose has a tip with bulbous ○ Fibers merging with the frontalis muscle appearance due to splayed alar cartilages ○ Plastic surgeons mostly modify this cartilage B. NASALIS during rhinoplasty 2 Parts: ○ Transverse Part Function: Compress the nostrils Origin: Maxilla Insertion: Aponeurosis of procerus ○ Alar Part Function: Flaring of the nostrils Origin: Maxilla Insertion: Alar Cartilage IV. BLOOD SUPPLY Figure 3. Alar Cartilage/Lower Lateral Cartilage C. VESTIBULE AND SKIN Dilated passageway Lined with skin and vibrissae (a.k.a. nose hair) ○ Vibrissae should be removed before nose surgeries Limen Nasi ○ Posterior part of vestibule ○ Bordered by the posterior part of the alar cartilage and the lower border of lateral cartilages ○ Narrowest part of the upper respiratory tract Skin of dorsum/sides loosely connected to the cartilages Figure 5. Branches of the Facial Artery Adherent at apex and alar cartilages III. MUSCLES Branches of the facial artery A. PROCERUS ○ Dorsal nasal branch of the ophthalmic artery (terminal branch of the ethmoid arteries) ○ Infraorbital branch of the maxillary artery from the infraorbital foramen Venous drainage to facial and ophthalmic veins V. NERVE SUPPLY Facial nerve for muscles of facial expression Ophthalmic nerve for sensation VI. LYMPHATIC DRAINAGE Drains ○ Anteriorly: 2 levels Ia - submental nodes Ib - submandibular nodes Figure 4. Muscles of the Nose ○ Posteriorly: to the retropharyngeal and upper deep cervical nodes GUINANGHAN, LABUGUEN, PAGUINTO Page 2 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 Nasoseptal deviation - deviation of septum either right or left Septoplasty - corrects nasoseptal deviation, straightens the septum Rhinoplasty - augment or reduce the nose B. BLOOD SUPPLY Figure 6. Lymphatic Drainage VII. NASAL SEPTUM A. OSTEOLOGY Figure 8. Facial Blood Supply Figure 7. Nasal Septum Bony Septum ○ Composed of: Perpendicular plate of the ethmoid (superior) Figure 9. Blood Supply to the Nasal Septum Separates left and right nasal cavity Arterial supply is derived mainly from maxillary artery Vomer (posterior) External Carotid Artery - give rise to sphenopalatine, and Forms the inferior portion of descending palatine (greater and lesser palatine) coming nasal septum from maxillary artery One of the unpaired facial ○ Branches of External Carotid Artery: bones Superior Thyroid Bony crest of maxilla and palatine bone Ascending Pharyngeal (inferior) Lingual Forms the palatine process of Facial the maxilla Occipital Cartilaginous Septum Posterior auricular ○ Composed of: Superficial temporal Quadrangular cartilage (anterior) - may Maxillary be deviated giving the nasal septum a Internal Carotid Artery - gives rise to the anterior and crooked appearance requiring surgery posterior ethmoid through ophthalmic artery to correct it ○ Superior Labial Artery - branch the facial artery Minor contribution from the lower and from ECA upper lateral alar cartilages GUINANGHAN, LABUGUEN, PAGUINTO Page 3 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 Kiesselbach’s Plexus/Little’s Area ○ Anteroposterior portion of the nasal septum where 4 vessels form a plexus: Sphenopalatine branch of the maxillary artery Greater palatine artery Superior labial branch of facial artery Anterior and posterior ethmoidal branches of the internal carotid artery Epistaxis (a.k.a. Nosebleed) ○ Occurs in the Little’s Area due to nose picking or cold inspiratory current causing drying of the mucosa (e.g. patients develop mucositis with prolonged use of oxygen) Figure 12. Trigeminal Nerve (Maxillary) D. LYMPHATIC DRAINAGE Anterior septum to the submandibular nodes Posteriorly to the retropharyngeal and anterior deep cervical nodes The remainder of the nasal cavity is drained by vessels that pass through the upper deep cervical nodes Nasal endoscopy - done in patients with lateral neck mass VIII. LATERAL WALL OF THE INTRANASAL CAVITY Consists of turbinates or concha (projections of bones) 3 in number, sometimes 4 Shell-shaped network of bones, vessels, and tissues within the nasal passages Responsible for humidifying and filtering the air we breathe ○ Breathing through the nose humidifies air while Figure 10. Epistaxis in the Kiesselbach’s Plexus breathing through the mouth dries the throat Erectile passages that respond to the nasal cycle C. NERVE SUPPLY ○ Congested turbinates Figure 11. Nerve Supply of the Nasal Septum Maxillary division of the trigeminal nerve - nerves of general Figure 13. Lateral Wall of the Intranasal Cavity sensation Anterior ethmoidal nerve - nerve supply to the anterior part A. LATERAL WALL of nasal cavity 3 major turbinates (inferior, middle, and superior) Nasal, nasopalatine, and palatine branches of the Bone comprises the following: pterygopalatine ganglion - nerve supply to posterior part of ○ Maxillary and ethmoid bone - anteriorly nasal cavity ○ Palatine and sphenoid bone - posteriorly Olfactory nerve - from special olfactory cells in the olfactory mucus membrane; ascend through cribriform plate GUINANGHAN, LABUGUEN, PAGUINTO Page 4 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 ○ Cribriform plate of the ethmoid bone - superior boundary ○ Palatine process of the maxilla - inferior boundary Figure 15. Osteomeatal Complex Composed of: 1. Ethmoid Bulla - rounded prominence caused by bulging Figure 14. Lateral Wall of the Right Nasal Cavity and underlying middle ethmoidal air sinuses 2. Maxillary Ostium B. INFERIOR MEATUS 3. Uncinated process Lateral to the inferior turbinate Receives the opening and drains the nasolacrimal duct Largest meatus Compact to lamellar bone Thicker posteriorly, anteriorly, inferiorly C. INFERIOR TURBINATE Composed of the conchal bone Consists of a separate bone attached to the maxillary bone at the middle wall of the maxillary sinus More cavernous spaces than mucus glands First to be seen in the lateral wall Fleshy and pinkish Largest turbinate Figure 16. Uncinate Process Separate bone covered by thick mucous membrane Nasolacrimal opening in the anterior portion of the lateral - Crescent shape part of the lateral wall of the lateral nasal wall of the inferior meatus cavity A slit-like opening is protected by a folded mucous - Attachment is important in endoscopic sinus surgery membrane (Plica lacrimalis or valve of Hasner) - Attached superiorly to lamina papyracea, some to the skull base and 1% to the middle turbinate D. MIDDLE MEATUS 4. Hiatus semilunaris - a semicircular-shaped opening Most important intranasally because: located on the lateral wall of the nasal cavity below the ○ It houses the Osteomeatal Complex (OMC) bulla; where the maxillary sinus opens into Area at the lateral nasal wall where the 5. Middle turbinate - landmark which forms the medial wall of osteal of the paranasal sinuses drain the ethmoid sinus into the nasal cavity except for your 6. Ethmoid infundibulum - groove, funnel-shaped channel sphenoid sinus Functional unit of the anterior ethmoid E. MIDDLE TURBINATE complex that represents the final Integral part of the ethmoid bone common pathways for drainage and Sometimes pneumatized (air-filled) ventilation ○ a.k.a. Concha Bulosa - aerated middle ○ The drainage from the anterior paranasal sinuses turbinate/unilateral or bilateral will go to this area and any blockage in the ○ Indication for surgery; becomes big enough to osteomeatal complex will usually result to block the osteomeatal complex (Sinusitis) sinusitis GUINANGHAN, LABUGUEN, PAGUINTO Page 5 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 The olfactory nerves from the olfactory mucous membrane ascend through the cribriform plate of the ethmoid bone to the olfactory bulbs. The nerves of ordinary sensation are branches of the ophthalmic division (V1) and the maxillary division (V2) of the trigeminal nerve Nerve supply of the nose is located at the superior turbinate; may be damaged by blunt force (punched to the nose) or traumatic injury. May lead to anosmia (inability to smell) or hyposmia (reduced ability to smell and detect odors) I. LYMPHATIC DRAINAGE Figure 17. Pneumatized Middle Turbinate/Concha Bulosa Drains anteriorly to the Submandibular Nodes Posteriorly to the Retropharyngeal and Upper deep cervical More mucus glands than cavernous spaces nodes (level 2 and 3) Consists of 2 parts: Osteomeatal complex represents the final common ○ Lateral Lamina/Lamina Basilaris pathway for drainage and ventilation of the frontal maxillary Posterior part of middle turbinate and anterior ethmoid cells Downward/backwards from anterior ○ Middle meatus of osteomeatal complex is the ethmoidal roof to a small crest of common drainage of the sphenoid, ethmoid, palatine bone maxillary, and frontal suture ○ Medial lateral ○ “What can block the osteomeatal complex?” Anterior part of the middle turbinate Infections Ascends upwards lining of the ethmoid Accumulation of too much mucus air cells Polyps - abnormal tissue growth ○ Most superior portion of the middle meatus is Cancer inferior to genu known as frontal recess. Ostia IX. PARANASAL SINUS of frontal sinus and some anterior ethmoid cells are located here F. SUPERIOR MEATUS AND TURBINATE Receives ostia from the posterior ethmoid cells A supreme turbinate can be seen above the superior turbinate on occasion Most superior ○ Air is black on a CT scan Where olfactory nerves are located ○ Spheno-ethmoidal recess Small area above the superior concha and in front of the body of sphenoid bone Figure 18. Location of the Paranasal Sinuses ○ Receives opening of sphenoid air sinus 4 types ○ Approximately ½ length of the middle turbinate ○ Maxillary - present at birth ○ Lies between superior and supreme turbinate ○ Ethmoid - present at birth ○ Sphenoid - appears later in life/developed after G. BLOOD SUPPLY birth Similar to septum ○ Frontal - appears later in life/developed after birth From Internal and External Carotid systems Air-filled extensions of the nasal cavity that is lined with Venous drainage - via the Sphenopalatine system mucoperiosteum; lined by mucosa/mucous membrane All paired H. NERVE SUPPLY Serve to lighten bones Drain into the nasal cavity Similar to septum Functions: Anterior Ethmoidal Nerve ○ Resonance of voice Branches of the Pterygopalatine and the Anterior Palatine ○ Increase surface area of olfactory membrane Nerves ○ Lightens the skull ○ Serve as “crumple zone” for the face in trauma GUINANGHAN, LABUGUEN, PAGUINTO Page 6 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 ○ Protects the brain from direct injury ○ Humidity and warm inspired air ○ Regulation of intranasal pressure ○ Shock absorber ○ Contribute to facial growth A. MAXILLARY BONE AND SINUS Figure 20. Level of the Floor of Maxillary Sinus in different stages of development ○ Medial nasal surface constitutes the floor of the pyramid and contains the maxillary meatus ○ Pterygopalatine Fossa Behind the posterior border of the maxilla Where the maxillary artery traverse Figure 19. Right Maxillary Sinus with the branches of trigeminal nerve and the autonomic nervous system Largest of the sinuses Clinical Correlation: Opens into the middle meatus via hiatus semilunaris In local surgery of the nasal Largest facial bone after the mandible bone, the pterygopalatine Forms most of the roof of the mouth, floor, and lateral wall fossa is palpated intraorally. It of the nasal cavity and floor of the orbit is located behind the last A.k.a. ANTRUM OF HIGHMORE upper molar, where lidocaine Anterior border of maxillary bone: CANINE DEPRESSION is injected to block the ○ Relatively very thin; gives easier access for the trigeminal nerve and other surgeon into the maxillary sinus for the caudal components of the autonomic lock procedure nervous system. Roof of sinus is usually thin and forms the floor of the orbit ○ Remaining space is filled with fibrous membrane Floor of the sinus is thick and encroached by dental roots ○ Related to the lacrimal canal anteriorly which is of the 2nd and 3rd molars (extraction of these teeth creates created between the maxilla, lacrimal bone, and an oromaxillary fistula which needs to be repaired) inferior concha Level of the floor of the maxillary sinus relative to the nasal ○ Nasolacrimal duct passes and drains into th pe floor anterior inferior meatus ○ Birth - sinus floor several mm higher than ○ The maxillary valve, also known as the intranasal cavity “nasolacrimal valve”, plays a role in preventing ○ 8-9 years - same level (intranasal floor and the backflow of secretions from the nasal cavity maxillary sinus) into the lacrimal duct system. It helps maintain a ○ Continued development - sinus lower than nasal one-way flow of tears, reducing the risk of floor due to pneumatization contamination and infection spreading from the nasal cavity to the eyes. ○ Average volume: 14.25 mL or 15 mL (largest) ○ Average dimensions: Height: 36-45 mm Width: 25-35 mm Length: 38-45 mm ○ Relations: Superior - orbit Inferior - upper dentition and palate Posterior - infra-temporal fossa or pterygopalatine fossa GUINANGHAN, LABUGUEN, PAGUINTO Page 7 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 Anterior - cheek with fat and facial walls from the middle turbinate, the orbit, to the musculature sphenoid sinus. ○ Blood supply, Nerve supply, and Lymphatic ○ 8-10 pairs of air cells between drainage ○ Lateral boundary: Lamina Papyracea (divides the Small arteries from the facial, maxillary, ethmoid and the eyes) infraorbital, and greater palatine ○ Basal lamella - posterior border of the middle arteries turbinate; the boundary of the posterior ethmoid Veins accompany these vessels to air cells anterior facial vein and pterygoid Agger Nasi cell plexus ( drainage) ○ Most anterior ethmoid cell Nerve supply is derived from ○ Latin: nasal mound infraorbital, superior alveolar, and ○ Most superior ethmoid cell greater palatine nerves ○ Latin: nasak mound Lymph drainage is to the ○ Most superior remnant of the first ethmoturbinal submandibular nodes but relatively ○ Mound or crest immediately anterior to the poorly developed insertion of the middle turbinate ○ Natural ostium (drains into the middle meatus Posterior and superior pneumatization through ethmoidal fundibulum; 3-4 mm in may cause narrowing of the frontal diameter) recess ○ Maxillary fontanelle - is composed of mucosa of Ethmoid Bulla/Bulla Ethmoidalis the lateral nasal wall and the mucosa of the ○ Anterior group of ethmoid cells maxillary sinus (antral irrigation) ○ Largest and most constant/non-variant ethmoid ○ Water’s View - to demonstrate maxillary sinuses air l and air fluid levels ○ Immediately posterior to Agar Nasi cells B. ETHMOID BONE AND SINUS Osteology ○ Extremely complex bone ○ Consists of 5 main parts Perpendicular plate Cribriform plate Crista galli 2 Lateral Labyrinths Figure 22. CT scan showing Bulla Ethmoidalis Haller Cells ○ Infraorbital ethmoid cells ○ Air cells at the bony orbital floor ○ Ethmoid cells that extend into the maxillary sinus above the ostium, pneumatize the medial and inferior orbital walls Figure 21. Posterior and Anterior view of the Ethmoid Bone Relations: ○ Divides the anterior cranial fossa and the nasal cavity ○ Divides orbital cavity (left and right) ○ Relates posteriorly to sphenoid sinus Ethmoid air cells ○ Labyrinth of small, pneumatized sinus cavities that are separated from each other by thin bony Figure 23. CT scan showing Haller Cells GUINANGHAN, LABUGUEN, PAGUINTO Page 8 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 Onodi Cells (Sphenoethmoid cells) ○ Term used when middle turbinate is pneumatized ○ Posterior ethmoid air cells (when middle turbinate has air inside; may cause ○ Located at the sphenoid, posterior to the ethmoid nasal obstruction) ○ Ethmoid cells that pneumatize lateral or posterior ○ Also applies to pneumatization of the superior to anterior wall of the sphenoid, commonly turbinate mistaken as sphenoidal cell ○ Formation may begin late in life Optic Nerve Tubercle ○ Bulge of the medial aspect of the bone surrounding the optic foramen ○ Can be seen in the posterior ethmoid, transition between the posterior ethmoid and sphenoid sinus, or sphenoid sinus itself Blood and Nerve Supply and Lymphatic Drainage Figure 24. CT-Scan showing Onodi Cells Hiatus Semilunaris Inferioris ○ Anatomic plane representing the free posterior margin of the uncinate process to the surface of the ethmoid bulla ○ A two-dimensional crescent shaped cleft ○ Lies behind uncinate process Hiatus Semilunaris Superioris ○ Crescent shape cleft between the ethmoid bulla and middle turbinate Figure 27. The Olfactory Nerve ○ The Suprabullar and Retrobullar Recess can be entered medially and inferiorly underneath the Vascular supply from the sphenopalatine and ethmoidal middle turbinate through the hiatus semilunaris arteries and drained by corresponding veins (posterior superior ethmoidal artery; Sphenoidal artery - Maxillary artery) Venous drainage: nasal veins, anterior ethmoidal vein, posterior ethmoidal vein Innervated by the anterior, posterior ethmoidal nerves and maxillary branches of the pterygopalatine ganglion Lymphatic drainage is into submandibular (anterior and middle ethmoidal cells) and retropharyngeal nodes (anterior and middle ethmoidal cells) C. SPHENOID BONE AND SINUS Osteology ○ Houses sphenoid sinus ○ Most posterior of the paranasal sinuses ○ Located at the center of the skull above the nasopharynx ○ Largest single bone in the skull base Figure 26. Location of Hiatus Semilunaris in relation to other sinuses ○ Composed of body, two wings, two inferior plates (lateral and medial pterygoid) Ethmoid Infundibulum ○ Variable in size and often asymmetric ○ A cleft or true three-dimensional space bordered ○ Sphenoid sinus is located approximately at the medially by the uncinate process and laterally by center of the skull above nasopharynx the lamina papyracea, the frontal process of the maxilla and the lacrimal Concha Bullosa GUINANGHAN, LABUGUEN, PAGUINTO Page 9 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 ○ Usually L-shaped ○ Thinnest at the orbital roof ○ 1% of population have no frontal sinus ○ The frontal sinus develops either from the frontal recess, which forms an ostium draining directly into the internal meatus, or from the ethmoidal cells, which may contribute to the formation of the frontal sinus duct ○ Last of the paranasal sinuses to develop Figure 28. Sphenoidal sinus (right and left) Relations: Relations: ○ Articulates with the cribriform plate ○ Form posterior wall (clivus) of ethmoid sinus ○ Intimately related with the ethmoidal labyrinth ○ Intimately related to the optic canal ○ Close relationship with the orbit ○ Posteriorly, the body articulates with the occipital ○ Opens into and is continuous with the bone infundibulum ○ Laterally lie the cavernous sinuses, internal ○ Drains through the frontal recess carotid artery, and cranial nerves II to VI ○ Trephination - boring a hole at the anterior wall to ○ Foms the roof of the nasopharynx get specimen ○ Superiorly to optic canal, Sella turcica and Most common site of mucocele pituitary gland formation Blood and Nerve supply and Lymphatic drainage ○ Drainage to middle meatus ○ Supraorbital and anterior ethmoidal arteries; supratrochlear artery ○ Includes anastomotic vein in the supraorbital notch Small vein that unites the Supraorbital and Superior Ophthalmic veins ○ Nerve Supply: Supraorbital nerve (Ophthalmic nerve) Supratrochlear nerve (Ophthalmic nerve) ○ Lymphatic drainage: Submandibular nodes ○ Caldwell View - to demonstrate the frontal ○ Sphenoethmoidal recess: small space into which sinuses the sphenoidal sinus and posterior Sethmoid sinus open DRAINAGE SYSTEM ○ Internal carotid artery and optic nerve lie at the lateral wall and other cranial nerves ○ Allows access to remove pituitary gland tumors (Sphenoidotomy) Blood and Nerve supply and Lymphatic drainage ○ Supplied by the superior ethmoidal vessels and nerves and the orbital branches of the pterygopalatine ganglion ○ Blood supply: Posterior ethmoidal artery (roof of the sinus); Sphenopalatine artery (floor of sinus) ○ Nerve supply: Trigeminal (1/11 division) ○ Lymphatic drainage to retropharyngeal nodes D. FRONTAL BONE AND SINUS Figure 29. Drainage of the Paranasal Sinus Cavities Osteology ○ Forms the forehead and orbital roof ○ Varying thickness GUINANGHAN, LABUGUEN, PAGUINTO Page 10 of 11  ANATOMY SAINT LOUIS UNIVERSITY P.11 The Nose and Paranasal Sinuses Dr. Baga | August 30, 2024 SOM 2028 CHECKPOINT 1. The nasal bone is bounded by this bone superiorly. 2. Posterior part of vestibule 3. This muscle shortens the nose and lowers the skin between eyebrows. 4. Origin of the nasalis 5. Anteroposterior portion of the nasal septum where four vessels form a plexus. 6. Anterior border of maxillary bone 7. Average volume of the maxillary sinus 8. Posterior border of the middle turbinate which is the boundary of the anterior and posterior ethmoid air cells 9. Largest single bone in the skull bone 10. Site of drainage of the frontal sinuses References Snell, R. S. (2012). Clinical anatomy by regions: Chapter 11 the head and neck (9th ed., pp 639-644). Lippincott Williams & Wilkins. 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