PRESENTATION ON ANATOMY OF NOSE FOR UNDERGRADUATES

Anatomy of nose

1. EMBRYOLOGY OF NOSE ANATOMY OF EXTERNAL NOSE,VESTIBULE AND NASAL SEPTUM PRESENTER:DR.SRIRAM. MODERATOR:DR.SANDEEP.S.

2. DEVELOPMENT OF NOSE The development of the nose needs to be studied in conjunction with the development of the face. Facial development takes place mainly between the 4th and 8th weeks of intrauterine life. The face develops from five facial swellings that surround the stomodeum or primitive mouth by the end of the 4th week. The swellings consist of a central unpaired process called the frontonasal process, a pair of maxillary and a pair of mandibular processes. The maxillary and mandibular processes are both subdivisions of the first pharyngeal arch.

3. FRONTONASAL PROCESS During the 4th week of development, after the formation of the head fold, two prominent bulges appear on the ventral aspect of the developing embryo, separated by the stomatodeum . They are: Developing brain cranially Pericardium caudally The floor of the stomatodeum is formed by the buccopharyngeal membrane, which separates it from the foregut. On each side, the stomatodeum is bounded by first arch.

4. Mesoderm covering the developing forebrain proliferates and forms a downward projection that overlaps the upper part of the stomatodeum . This downward projection is called the frontonasal process .

5. During the 5th week, a pair of ectodermal thickenings appear on the frontonasal process. These are called the nasal placodes. In the 6th week, the ectoderm in the center of each nasal placode invaginates to form an oval nasal pit. The raised rims of these nasal pits form the lateral and medial nasal processes.

6. During the 6th and 7th weeks, the maxillary processes on either side increase in size and grow medially. This medial migration of the maxillary processes causes the medial nasal processes to move towards each other. As the maxillary processes grow medially, they fuse first with the lateral nasal process and then with the medial nasal process. This separates the nasal pits from the stomodeum.

7. The medial nasal processes fuse with each other to form the intermaxillary process. The central tissues of the intermaxillary process get pushed upwards to form the nasal prominence characteristic of human beings. The intermaxillary process forms the central bridge of the nose and the central portion of the upper lip called the philtrum.

8. At the end of the 6th week, the nasal pits deepen and coalesce to form a single cavity behind the intermaxillary process. This cavity is initially separated from the stomodeum lying below it by a thin membrane called the oronasal membrane. This membrane ruptures during the 7th week to form the primitive choana .

9. The intermaxillary process grows backward to form the nasal septum. The lateral nasal processes enlarge to form the nasal alae. They also grow backwards to form the lateral nasal wall. This developing lateral nasal wall shows multiple anteroposterior elevations or ridges, which are finally reduced to three or occasionally four turbinates . This first ridge, the maxilloturbinal , develops in the seventh week and gives rise to the inferior turbinate. During the eighth gestational week, a series of 5 to 6 ridges appear superior to the maxilloturbinal ; through regression and fusion, these ridges form 3 to 5 ethmoturbinals.

10. The first ethmoturbinal gives rise to the agger nasi from its ascending portion, and to the uncinate process from its descending portion. The remainder of the first ethmoturbinal regresses. The second ethmoturbinal forms the middle turbinate while the third ethmoturbinal forms the superior turbinate. The fourth and fifth ethmoturbinals typically regress, but in some individuals persist and fuse to form the supreme turbinate.

11. The maxillary processes fuse with the lateral nasal processes. The junction of their fusion is marked by a groove called the nasolacrimal or naso -optic groove. By the 7th week, this groove invaginates into the underlying mesenchyme to form the nasolacrimal duct. The floor of the nasal cavity, which is the hard palate, is formed during the 8th and 9th week.

12. The medial surfaces of the maxillary processes form thin medial extensions called palatine shelves. These shelves first grow downwards on either side of the developing tongue; but by the end of the 9th week, they rotate upwards into a horizontal position. They then fuse with each other in the midline and with the primary palate anteriorly to form the secondary palate.

13. The secondary palate also fuses with the lower border of the developing nasal septum. The nasal cavity is thus divided into two nasal passages, which open into the pharynx behind the secondary palate through openings called the definitive choanae. The mandibular processes grow medially and fuse in the midline to form the lower lip and jaw.

14. SUMMARY OF THE EMBRYONIC PRECURSORS TO THE FACIAL STRUCTURES Processes Structures formed Frontonasal Forehead, bridge of nose, medial and lateral nasal prominences Maxillary Cheeks, lateral portion of upper lip Medial nasal Philtrum of upper lip, crest and tip of nose, septum Lateral nasal Alae of nose, lateral nasal wall Mandibular Lower lip and jaw

15. DEVELOPMENTAL ANAMOLIES Harelip : It is the defect of upper lips – Unilateral harelip : failure of fusion of maxillary process with medial nasal process on one side. – Bilateral harelip : failure of fusion of both maxillary processes with the medial nasal process. – Midline cleft of upper lip : Defective development of the lowermost part of the frontonasal process may give rise to a midline defect of the upper lip. Cleft of lower lip : When the two mandibular processes do not fuse with each other the lower lip shows a defect in the midline.

16. Oblique facial cleft : Nonfusion of the maxillary and lateral nasal process gives rise to a cleft running from the medial angle of the eye to the mouth. The nasolacrimal duct is not formed. Macrostomia : Inadequate fusion of the mandibular and maxillary processes with each other may lead to an abnormally wide mouth. Microstomia : Excessive fusion may result in a small mouth.

17. The nose may be bifid. This may be associated with median cleft lip. These occur due to bifurcation of the frontonasal process. Occasionally one half of it may be absent. Rarely the nose forms a cylindrical projection, or proboscis jutting out from just below the forehead. This anomaly may sometimes affect only one half of the nose and is usually associated with fusion of the two eyes ( cyclops ).

18. TREACHER COLLINS SYNDROME : .It is an autosomal dominant genetic disorder. First arch may remain underdeveloped on one or both sides, affecting the lower eyelid (coloboma type defect), the maxilla, the mandible, and the external ear. The prominence of the cheek is absent and the ear may be displaced ventrally and caudally. Presence of cleft palate and of faulty dentition. This condition is also called as mandibulofacial dysostosis or first arch syndrome .

19. ANATOMY OF EXTERNAL NOSE The external nose is a pyramidal structure located in midline of the face and attached to the facial skeleton. Root . Dorsum. Bridge. Alae. Columella.

20. It consists of osteocartilagenous framework covered by muscles and skin. OSTEOCARTILAGENOUS FRAMEWORK: Bony part Cartilaginous part

21. SKIN AND SOFT TISSUE: The skin and soft tissue covering the nose vary in thickness: The skin over the dorsum and sides of the nose is thin and loosely adherent to the underlying framework. The nasal skin becomes thicker and more adherent towards the nasal tip and alar cartilages where it contains numerous sebaceous glands. The extension of the facial SMAS layer continues over the nose as numerous muscles of external nose which function to compress, dilate, depress or elevate the nostrils and nasal tip.

22. Skin over the nose is separated from the underlying osteocartilaginous framework by four layers. Superficial fatty panniculus. Fibromuscular layer . Deep fatty layer. Periosteum or perichondrium.

23. SUPERFICIAL MUSCULO APONEUROTIC SYSTEM Superficial fatty layer is directly connected to the dermis. Fibromuscular layer comprises the nasal SMAS. Deep fatty layer lies deep to the SMAS and contains the neurovascular system. Incisions in rhinoplasty are given deep to all these layers since blood vessels run in deep fatty layer.

24. BONY AND CARTILAGINOUS PART: Upper one-third is bony and it consists of two nasal bones which meet in the midline and rest on the upper part of the nasal process of the frontal bones and are themselves held between the frontal processes of the maxilla.

25. CARTILAGINOUS SKELETON OF EXTENAL NOSE: It consists of upper lateral cartilages lower lateral cartilages lesser alar cartilages septal cartilage

26. Lateral nasal cartilage : Triangular in shape Anterior margin is thicker than the posterior margin . Upper part fuses with the septal cartilage. Superior margin attaches with nasal bone and frontal process of maxilla . Inferior margin is connected by fibrous tissue to the lateral crus of the major alar cartilage. Laterally-attached indirectly to margins of piriform aperture by loose fibro alveolar connective tissue which may contain one or more sesamoid cartilage.

27. MAJOR ALAR CARTILAGE: Major alar cartilage is highly complex ,thin flexible plate which integral to nasal lobule. It lies below the upper lateral cartilage and curves acutely around the anterior part of its naris. Medial part the narrow medial crus is loosely connected by fibrous tissue to its contralateral counterpart and to the anterioinferior part of the septal cartilage . Intermediate crus forms the margin of the apex of the nostril. The domes give rise to tip deforming point of the nose. The lateral crus lies lateral to the naris and runs superolaterally away from the margin of the nasal ala.

28. Upper border of the lateral crus af the major alar cartilage is attached by fibous tissue to the lower border of lateral nasal cartilage. Lateral border connects to the frontal process of maxilla by a tough fibrous membrane containing three or four minor alar cartilages. The lateral crus is shorter than the lateral margin of the naris; the most lateral part of the margin of ala nasi is fibroadipose tissue covered by skin . In front the angulations between the medial and lateral crurae of the major alar cartilage are separated by notch palpable at the tip of the nose.

29. COLUMELLA: It extends between the upper lip and tip of the nose. It consists of paired medial crura with variable length producing projecting or depressed tip. Anteriorly the diverging crura form an angle of 30degrees for tip formation. Posteriorly it diverges to receive septal angle, adjoining septal cartilage and anterior nasal spine. The shape of columella depends on the size and shape of medial crura

30. MUSCLES OF NOSE: PROCERUS: ORIGIN: Nasal bone and upper part of lateral nasal cartilage. INSERTION: Skin of forehead between eyebrows and on bridge of the nose. ACTIONS: Transverse wrinkles. VASCULAR SUPPLY : Branches from facial artery. NERVE SUPPLY : Temporal and zygomrtic branches from the facial nerve .

31. COMPRESSOR NARIS ORIGIN : Maxilla just lateral to nose. INSERTION : Aponeurosis across dorsum of nose. ACTIONS : Nasal aperture compressed. DILATOR NARIS : ORIGIN :Maxilla over the lateral incisor. INSERTION :alar cartilage of nose. ACTIONS : Nasal aperture dilated. VASCULAR SUPPLY : Suppled by branches from facial and from infraorbital branches of the maxillary artery. NERVE SUPPLY : Buccal branch of facial nerve and zygomatic branch of facial nerve.

32. DEPRESSOR SEPTI : ORIGIN : Maxilla over the medial incisor. INSERTION : lower mobile part of septum. ACTIONS :Nose pulled inferiorly. VASCULAR : supplied by the superior labial branch of the facial artery. NERVE : Innervated by the buccal branch, and sometimes by the zygomatic branch, of the facial nerve

33. LEVATOR LABII SUPERIORIS ALAEQUE NASI: ORIGIN : Arises from the upper part of the frontal process of the maxilla . INSERTION : Upper lip and alar cartilage of nose. ACTION : lifts the upperlip and dilates the nostril. VASCULAR SUPPLY :facial artery and the infraorbital branch of the maxillary artery. NERVE SUPPLY : zygomatic and superior buccal branches of the facial nerve.

34. BLOOD SUPPY : Nasal skin receives its blood supply from branches of the facial, ophthalmic and infraorbital arteries. The alae and lower part of the nasal septum are supplied by lateral nasal and septal branches of the facial artery. The lateral aspects and dorsum of the nose are supplied by the dorsal nasal branch of the ophthalmic artery and the infraorbital branch of the maxillary artery.

35. VENOUS SUPPLY : The frontomedian region of the face, including the nose, drains to the facial vein. The orbito palpebral area of the face, including the root of the nose, drains to the ophthalmic veins.

36. DANGER AREA OF FACE : The connections of the veins of the nose, upper lip and cheek (the ‘danger triangle of the face’) with the drainage area of the valveless ophthalmic veins, and hence to the cavernous sinus, are clinically significant because they can be a route for spreading infection that initiates thrombosis of the major intracranial sinuses.

37. NERVE SUPPLY: Infratrochlear and external nasal branches of the nasociliary nerve (ophthalmic division, trigeminal nerve). The nasal branch of the infraorbital nerve (maxillary division, trigeminal nerve).

38. NASAL CAVITY: The nasal cavity is an irregular space between the roof of the mouth and the cranial base. Each half of the nasal cavity has a vestibule, roof, floor, medial (septal) and lateral walls

39. VESTIBULE: It is the anterior and inferior part of nasal cavity. It is lined by skin and contains sebaceous glands, hair follicles and the hair called vibrissae. The upper limit is marked by limen nasi which is also called as nasal valve. The limen nasi is the location where the marginal incision is made during external approach rhinoplasty. Boundaries of limen nasi: Laterally by lower border of ULC and fibrofatty tissue and anterior end of inferior turbinate. Medially by cartilaginous septum. Caudally by floor of pyriform aperture.

40. ROOF The roof is horizontal in its central part and slopes downwards in front and behind . The anterior slope is formed by the nasal spine of the frontal bones and by the nasal bones. The central region is formed by the cribriform plate of the ethmoid bone, which separates the nasal cavity from the floor of the anterior cranial fossa.

41. It contains numerous small perforations that transmit the olfactory nerves and their ensheathing meningeal layers, and a separate anterior foramen that transmits the anterior ethmoidal nerve and vessels. The height of the cranial base is greatest anteriorly; hence, when dissecting along the cranial base during sinus surgery, it is safest to do so from back to front, addressing the lower-lying posterior region first to avoid inadvertent Intracranial penetration. Posteriorly, the roof of the nasal cavity is formed by the anterior aspect of the body of the sphenoid, interrupted on each side by an opening of a sphenoidal sinus, and the sphenoidal conchae or superior concha.

42. FLOOR: The floor of the nasal cavity is smooth and concave transversely, and slopes up from the anterior to the posterior apertures. The greater part is formed by the palatine processes of the maxillae, which articulate posteriorly with the horizontal plates of the palatine bones at the palatomaxillary suture .

43. Anteriorly, near the septum, a small infundibular opening in the bone of the nasal floor leads into the incisive canals that descend to the incisive fossa; this opening is marked by a slight depression in the overlying mucosa. The floor of the nose may be deficient as a result of congenital clefting of the hard and/or soft palate.

44. MEDIAL WALL: The medial wall of each nasal cavity is the nasal septum, a thin sheet of bone (posteriorly) and cartilage (anteriorly) that lies between the roof and floor of the cavity .

45. NASAL SEPTUM The posterosuperior part of the septum and its posterior border are formed by the vomer, which extends from the body of the sphenoid to the nasal crest of the palatine bones and maxilla . The nasopalatine nerves and vessels groove its surface.

46. The anterosuperior part of the septum is formed by the perpendicular plate of the ethmoid, which is continuous above with the cribriform plate and the frontal bone. Other bones septum at the upper and lower limits of the medial wall are the nasal bones and the nasal spine of the frontal bones (anterosuperior), the rostrum and crest of the sphenoid (posterosuperior), and the nasal crests of the maxilla and palatine bones (inferior).

47. CARTILAGINOUS SEPTUM The septal cartilage is almost quadrilateral and may extend back (especially in children) for some distance between the vomer and the perpendicular plate of the ethmoid. Its anterosuperior margin is connected above to the posterior border of the internasal suture, and the distal end of its superior portion is continuous with the upper lateral cartilages.

48. The anteroinferior border is connected by fibrous tissue on each side to the medial crurae of the major alar cartilage. Anteroinferiorly , the cartilaginous septum is attached to the anterior nasal spine, which is formed by anterior projections of each maxillary crest, and it has a strong, tongue-in-groove attachment with the premaxilla and vomer.

49. . The cartilaginous septum anterior to the spine is essential in tip support and should not be excised during septal surgery in order to prevent columellar retraction or loss of tip support. The posterosuperior border joins the perpendicular plate of the ethmoid, while the posteroinferior border is attached to the vomer and, anterior to that, to the nasal crest and anterior nasal spine of the maxilla.

50. The anteroinferior part of the nasal septum between the nares is devoid of cartilage and is therefore called the membranous septum; it is continuous with the columella anteriorly. Above the incisive canals, at the lower edge of the septal cartilage, a depression pointing downwards and forwards is all that remains of the nasopalatine canal, which connected the nasal and buccal cavities in early fetal life. Near this recess, a minute orifice leads back into a blind tubule, 2–6 mm long, which lies on each side of the septum and houses remnants of the vomeronasal organ.

51. BLOOD SUPPLY: The anterior and posterior ethmoidal branches of the ophthalmic artery supply the ethmoidal and frontal sinuses and the roof of the nose (including the septum).

52. The sphenopalatine branch of the maxillary artery supplies the mucosa of the turbinates , meatuses and posteroinferior part of the nasal septum, i.e. it is the principal vessel supplying the nasal mucosa.

53. The greater palatine branch of the maxillary artery supplies the region of the inferior meatus. A branch crosses the sphenoidal rostrum, below its natural ostium, to supply the nasal septum.

54. KISSELBACH’S PLEXUS It is the most common location of epistaxis due to its rich vascular supply and susceptibility to injury. It is present in the anterior inferior part of nasal septum. The anterior ethmoid artery, septal branch of superior labial artery, septal branch of sphenopalatine artery and greater palatine artery contribute to Kisselbach’s plexus.

55. VENOUS DRAINAGE: A rich submucosal cavernous plexus is especially dense in the posterior part of the septum and in the middle and inferior turbinates . Numerous arteriovenous anastomoses are present in the deep layer of the mucosa and around the mucosal glands. The cavernous turbinate plexuses resemble those in erectile tissue; the nasal cavity is susceptible to blockage, should they become engorged. Veins from the posterior part of the nose generally pass to the sphenopalatine vein that runs back through the sphenopalatine foramen to drain into the pterygoid venous plexus.

56. The anterior part of the nose is drained mainly through veins accompanying the anterior ethmoidal arteries, and these veins subsequently pass into the ophthalmic or facial veins. Injection of vasoconstrictive agents or corticosteroids during surgery, particularly to the inferior turbinates , may permit access to the intracranial and ophthalmic circulations. A few veins pass through the cribriform plate to connect with those on the orbital surface of the frontal lobes of the brain. When the foramen caecum is patent, it transmits a vein from the nasal cavity to the superior sagittal sinus.

57. LYMPHATIC DRAINAGE : Lymph vessels from the anterior region of the nasal cavity pass superficially to join those draining the external nasal skin and end in the submandibular nodes. The rest of the nasal cavity, paranasal sinuses, nasopharynx and pharyngeal end of the pharyngotympanic tube all drain to the upper deep cervical nodes, either directly or through the retropharyngeal nodes. The posterior nasal floor probably drains to the parotid nodes.

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