Regional Anatomy II Week 6 SU22 PDF

Week 6 Nose, nasal cavity, sinuses Nose ● ● ● ● ● ● ● Upper end is known as the root and is continuous with the forehead The tip of the nose is the apex Dorsum extends from root to apex Nares - aka nostrils, two inferior apertures Each nostril is bordered laterally by the ala of the nose Supporti...

Week 6 Nose, nasal cavity, sinuses Nose ● ● ● ● ● ● ● Upper end is known as the root and is continuous with the forehead The tip of the nose is the apex Dorsum extends from root to apex Nares - aka nostrils, two inferior apertures Each nostril is bordered laterally by the ala of the nose Supporting framework is composed of bone and hyaline cartilage Bony framework supports upper nose and consists of nasal bones and frontal processes of maxilla Nose Cartilaginous framework consists of three major pieces that are connected to each other and to bones by fibrous tissue. 1. 2. One septal cartilage forms the anterior portion of the nasal septum and has two lateral processes. They are triangular in shape and located below the inferior border of the nasal bones Two major alar cartilages. U-shaped lateral and medial crura that form the lateral and medial borders of the 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 Two types - 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, two lateral walls, and a midline partition (nasal septum) that divides the nasal cavity into right and left parts Opens anterior on the face via the nares (nostrils) Communicates posteriorly with the nasopharynx via the posterior nasal apertures (choanae) Vestibule is lined with skin and contains stiff hairs Nasal Cavity Functions: 1. 2. 3. Olfaction Conditioning of inspired air (filtration, humidification, warming) Reception of secretions from paranasal air sinuses and nasolacrimal duct through their corresponding meatus Nasal Cavity Relationships: ● ● ● ● Roof - anterior cranial fossa (separated by cribriform plate) Lateral ethmoidal air cells, orbit, and maxillary sinus Floor is the palate Communicates with the nasopharynx Nasal Cavity Composition of the nasal cavity bony walls include: Floor - Hard palate ● ● Maxilla Palatine bones - horizontal plate Nasal Cavity Medial wall (nasal septum): ● ● ● Perpendicular plate of ethmoid Vomer Septal cartilage Nasal Cavity Lateral wall: ● ● ● ● ● ● Maxilla Lacrimal bone Inferior nasal concha Ethmoid Perpendicular plate of palatine Medial pterygoid plate Nasal Cavity Lateral wall: Three scroll-like bony projections named superior, middle, and inferior nasal conchae. The superior and middle conchae are extensions of the ethmoid. The inferior concha is an extension of the maxilla. The space between each concha and lateral wall is called the “meatus” (superior, middle, and inferior). Drainage of sinuses and nasolacrimal duct occurs here. Clinical Considerations Why do you think that babies or young children rarely experience “sinus problems”? Paranasal Sinuses Pneumatic spaces in frontal, maxilla, ethmoid, and sphenoid bones lined by a mucous membrane continuous with that of the nasal cavity. They drain into the nasal cavity. Sinuses develop as envaginations of nasal mucosa that invades bone surrounding nasal cavity, causing progressive bone resorption. At birth, the sinuses are rudimentary. There is a slow, continuous growth during childhood and a rapid growth during adolescence and attain maximum size in adulthood. Functions: ● ● Resonating chambers for voice Lighten skull bones Maxillary Sinus ● ● ● Largest paranasal sinus Lies within body of maxilla Relationships: ○ ○ ○ ● Superior - orbit and its contents Medial - nasal cavity (maxillary ostium located high in medial wall and provides poor drainage in erect posture) 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. Frontal Sinuses ● ● ● ● Located within frontal bone, behind the superciliary arches Vary in size and are rarely symmetrical Usually extend superiorly into frontal squama and posteriorly into orbital plates (roof of orbit) Opens into middle nasal meatus Ethmoidal Air Cells ● ● ● ● ● Thin-walled spaces within ethmoidal labyrinths Number of cells varies from 3 - 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 Sphenoid Sinuses ● ● ● ● ● Located posterior to upper part of nasal cavity, within the body of the sphenoid Related superiorly to pituitary gland and optic chiasm Related laterally to cavernous sinus and internal carotid artery Vary in size and are rarely symmetrical Open into corresponding sphenoethmoidal recess Nasal Cavity Innervation Summary Nasal Cavity Vasculature Internal carotid artery branches: ● ● Anterior ethmoidal artery Posterior ethmoidal artery External carotid artery branches: ● ● ● ● Sphenopalatine artery Greater palatine artery Superior labial artery Lateral nasal arteries Main sources from external and internal carotid branches: sphenopalatine and anterior ethmoidal arteries 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 in a space referred to as Kiesselbach’s area. It is a common site of epistaxis (nosebleed). Veins form a plexus in submucosa that drains into the pterygoid venous plexus (via sphenopalatine vein), facial vein, and superior ophthalmic vein (via anterior and posterior ethmoidal veins)