Nasal Cavity and Paranasal Sinuses Objectives 1 Name

Nasal Cavity and Paranasal Sinuses

Objectives 1. Name the parts of the nose and the structures that form its skeleton 2. Name the bony structures that form the walls of the nasal cavity 3. Name the openings found in each of the nasal meatuses and describe the anatomical features of the lateral wall of the middle nasal meatus 4. Describe the location and functions of the olfactory and respiratory parts of the nasal mucosa 5. Describe the blood and nerve supply of the nasal cavity 6. Name the paranasal sinuses and list their functions 7. Describe the location, anatomical relations, communication with the nasal cavity and blood and nerve supply of the paranasal sinuses 8. Discuss common disorders affecting the nasal cavity and paranasal sinuses

Nose • pyramidal in shape • its upper end is known as root and is continuous with forehead • its free tip is known as apex • dorsum: extends from root to apex, in midline • 2 inferior apertures called nares (nostrils) • each nostril is limited laterally by ala of nose • supporting framework of nose is composed of bone and hyaline cartilage • bony framework supports upper part of nose and consists of nasal bones and frontal processes of maxillae

Nose Cartilaginous framework support consisting of 3 major pieces that are connected to each other and to bones by fibrous tissue. 1. One septal cartilage forms anterior part of nasal septum and has 2 lateral processes (triangular in shape, located below the inferior border of nasal bones) 2. Two major alar cartilages: U-shaped with lateral and medial crura and form lateral and medial borders of nostrils

Nasal Cavity Nasal mucosa: • lines entire nasal cavity, except vestibule • firmly bound to periosteum and perichondrium of supporting structures • continuous with mucosal lining of nasopharynx, paranasal air sinuses and nasolacrimal duct • types of mucosa: olfactory and respiratory • olfactory mucosa: lines highest part of roof and adjacent parts of septum and lateral wall and contains olfactory receptor cells • respiratory mucosa lines rest of nasal cavity and is covered by respiratory epithelium (pseudostratified, columnar, ciliated)

Nasal Cavity • chamber consisting of bony and cartilaginous walls, covered with mucosa • has a floor, a roof, 2 lateral walls and a midline partition (nasal septum), which divides nasal cavity into right and left parts • opens anteriorly on face via nares (nostrils) • communicates posteriorly with pharynx (nasopharynx) via posterior nasal apertures (choanae) • vestibule is lined with skin and contains stiff hairs.

Nasal Cavity Functions: 1. Olfaction 2. Conditioning of inspired air (filtration, humidification, warming) 3. Reception of secretions from paranasal air sinuses and nasolacrimal duct

Relationships: • superior: anterior cranial fossa (separated by cribriform plate) • lateral to upper part of nasal cavity: ethmoidal air cells and orbit • lateral to lower part of nasal cavity: maxillary sinus

Nasal Cavity Relationships (cont. ): • inferior: oral cavity (separated by hard palate) • posterior: nasopharynx (communicates via choanae)

Composition of bony walls: Floor: hard palate (palatine processes of maxillae and horizontal plates of palatine bones)

Medial wall (nasal septum): perpendicular plate of Ethmoid and Vomer (smaller contributions from sphenoid, maxilla and palatine)

Nasal Cavity Composition of walls (cont. ): Lateral wall: maxilla, lacrimal bone, inferior nasal concha, ethmoidal labyrinth, perpendicular plate of palatine and medial pterygoid plate.

Lateral Wall continued Three scroll-like bony projections named superior, middle and inferior nasal conchae (superior and middle conchae belong to ethmoid, inferior concha is a separate bone) • space between each concha and lateral wall is called meatus named superior, middle and inferior. • sphenoethmoidal recess: part of nasal cavity located above and behind superior nasal concha

Lateral Wall

Medial Wall Netter’s Plate 38

Paranasal Sinuses Pneumatic spaces in frontal, maxilla, ethmoid and sphenoid bones, lined by a mucous membrane continuous with that of nasal cavity. Sinuses develop as evaginations of nasal mucosa that invades bone surrounding nasal cavity causing progressive bone resorption. At birth, sinuses are rudimentary. There is a slow, continuous growth during childhood and a rapid growth during adolescence. Sinuses attain maximum size in adulthood. Functions: • Resonating chambers for voice • Lighten skull bones

Maxillary Sinus Largest of paranasal sinuses Lies within body of maxilla. Roughly pyramidal in shape. Its’ base is directed medially, toward nasal cavity while its apex is directed laterally, toward zygomatic bone Relationships: • superior: orbit and its contents (infraorbital canal runs within superior wall of sinus) • medial: nasal cavity (maxillary ostium located high in medial wall and provides poor drainage in erect posture)

Maxillary Sinus Relationships (cont. ): • inferior: alveolar process of maxilla and roots of maxillary teeth Communicates with middle nasal meatus via an opening located in lower part of semilunar hiatus. • nerve supply: superior alveolar nerves (from V 2) • blood supply: superior alveolar arteries (branches of maxillary and infraorbital arteries)

Frontal Sinuses • located within frontal bone, behind superciliary arches • vary in size and are rarely symmetrical • usually extend superiorly into frontal squama and posteriorly into orbital plates (roof of orbit) • open into corresponding middle nasal meatus • nerve supply: supraorbital nerve (branch of frontal nerve, from V 1) • blood supply: supraorbital artery (branch of ophthalmic artery)

Ethmoidal Air Cells • thin-walled spaces within ethmoidal labyrinths • number of cells varies from 3 to 18 • anterior cells open into infundibulum of middle nasal meatus • middle cells open on surface of ethmoidal bulla of middle nasal meatus • posterior cells open into superior nasal meatus • nerve supply: anterior and posterior ethmoidal nerves (branches of nasociliary nerve, from V 1) • blood supply: anterior and posterior ethmoidal arteries (branches of ophthalmic artery)

Sphenoidal Sinuses • located posterior to upper part of nasal cavity, within body of sphenoid • related superiorly to pituitary gland optic chiasm • related laterally to cavernous sinus and internal carotid artery • vary in size and are rarely symmetrical • open into corresponding sphenoethmoidal recess • nerve supply: posterior ethmoidal nerve (branch of nasociliary nerve, from V 1), pharyngeal nerve (from pterygopalatine ganglion that contains V 2 sensory fibers) • blood supply: posterior ethmoidal artery (branch of ophthalmic artery), pharyngeal branch of maxillary artery

Nasal Cavity Communications of nasal meatus: The superior meatus communicates with the posterior ethmoidal air cells via small orifices in its lateral wall.

The middle meatus: • Ethmoidal bulla: elevation in lateral wall of middle meatus caused by middle ethmoidal air cells (openings of middle ethmoidal air cells are found on ethmoidal bulla) • semilunar hiatus: curved cleft anterior and inferior to ethmoidal bulla • ostium of maxillary sinus located in lower part of semilunar hiatus

Nasal Cavity Communications of nasal meatuses (cont. ) Middle meatus (cont. ): The superior end of semilunar hiatus leads into a curved channel known as infundibulum that receives openings of anterior ethmoidal air cells. In some individuals, the infundibulum also receives opening of frontal sinus. In others, infundibulum has superior blind end, and frontal sinus opens directly into anterior part of middle nasal meatus.

Inferior meatus: • Opening of nasolacrimal duct is located in anterior part of its lateral wall • Sphenoidal sinus opens into sphenoethmoidal recess

Review Plate

Review Plate

Nasal Cavity Innervation • Branches of ophthalmic and maxillary nerves • Anterior ethmoidal nerve: branch of nasociliary nerve (from ophthalmic nerve) passes from orbit to anterior cranial fossa via anterior ethmoidal foramen runs forward on cribriform plate to leave anterior cranial fossa and enters nasal cavity via small slit at side of crista galli. It divides into internal and external nasal branches with internal branches supply mucosa of anterior parts of septum and lateral wall. The external nasal nerve supplies skin of lower part of nose

Nasal Cavity • Innervation (cont. ): • posterolateral nasal branches: originate from pterygopalatine ganglion and greater palatine nerve to supply mucosa of posterior part of lateral wall • nasopalatine nerve: supplies mucosa of posterior part of nasal septum

Special sensory nerve supply: Olfactory receptor cells are bipolar neurons located in olfactory mucosa. The peripheral processes (dendrites) end in a dilation called (olfactory knob) It gives rise to nonmotile cilia, which spread over mucosal surface. Central processes (axons) join to form olfactory nerves that pass through openings of cribriform plate to end in the olfactory bulb.

Nasal Cavity Vasculature: • Main sources: sphenopalatine and anterior ethmoidal arteries 1. sphenopalatine artery: terminal branch of maxillary artery It supplies posterior parts of lateral wall and septum 2. anterior ethmoidal artery: branch of ophthalmic artery supplies anterior parts of lateral wall and septum • Minor sources: posterior ethmoidal artery, superior labial artery (branch of facial artery), and greater palatine artery

Nasal Cavity Vasculature (cont. ): On anterior part of septal cartilage, septal branches of sphenopalatine, greater palatine, anterior ethmoidal and superior labial arteries anastomose with each other which is known as Kiesselbach’s area. It is common site of epistaxis (nosebleed) Veins: form rich plexus in submucosa that drains is into the pterygoid venous plexus (via sphenopalatine vein), facial vein, and superior ophthalmic vein (via anterior and posterior ethmoidal veins)

Objectives 1. Name the parts of the nose and the structures that form its skeleton 2. Name the bony structures that form the walls of the nasal cavity 3. Name the openings found in each of the nasal meatuses and describe the anatomical features of the lateral wall of the middle nasal meatus 4. Describe the location and functions of the olfactory and respiratory parts of the nasal mucosa 5. Describe the blood and nerve supply of the nasal cavity 6. Name the paranasal sinuses and list their functions 7. Describe the location, anatomical relations, communication with the nasal cavity and blood and nerve supply of the paranasal sinuses 8. Discuss common disorders affecting the nasal cavity and paranasal sinuses