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anatomy of nose¶nasal sinuses.pdf
- 1. Anatomy and physiology of the nose and paranasal sinuses External Nose: Composed of two parts: Upper bony part (upper one third): Composed of the nasal process of the maxillary bones and the nasal process of the frontal bone (forehead) that articulate together in the middle with two nasal bones Lower cartilaginous part (lower two thirds) Flexible Framed by the lateral, greater alar, and lesser alar cartilages Dense fibrous connective tissue supports the rounded lateral walls of the nostrils, which are called ala Internal Nose Anterior aperture of the nose called nostril (nares) while the posterior aperture called choana which connects the nose to the nasopharynx The anterior part of the nasal cavity called vestibule which separated into 2 parts by collumella and lines by stratified squamous epithelium and contains small hairs called vibrissae The nasal cavities line by columnar epithelium The nasal septum divides internal nose into right and left nasal cavities. The floor of the nasal cavity is the superior portion of the hard palate. The roof of the nasal cavity is the ethmoid bone. The lateral walls of the internal nose are formed by turbinates. The turbinates curl medially and downward into the nasal cavity. There are three on each side inferior, middle, and superior turbinates.Each turbinate has a corresponding space called the meatus, which receives drainage from specific areas: Inferior meatus receives drainage from the nasolacrimal duct. Middle meatus receives drainage from the maxillary, anterior ethmoid, and frontal sinuses. Superior meatus receives drainage from the posterior ethmoid sinuses.
- 2. Nasal Septum: Composed of quadrangular septal cartilage anteriorly, perpendicular plate of ethmoid posterosuperiorly and vomer bone posteroinferiorly. Nasal septum Separates the nose into 2 nasal cavities. Internal Nose Blood Supply Two vascular trunks of the common carotid artery: External carotid artery, which has the following branches: Sphenopalatine artery Greater palatine artery Superior labial artery Angular artery Internal carotid artery, which has the following branches: Anterior ethmoid artery from the ophthalmic artery Posterior ethmoid artery from the ophthalmic artery Kiesselbachs plexus (Littles area): Most common site for anterior epistaxis Four arteries anastomose to form this area: Anterior ethmoidal artery (from the ophthalmic artery) Sphenopalatine artery (terminal branch of the maxillary artery) Greater palatine artery (from the maxillary artery) Septal branch of the superior labial artery (from the facial artery) Woodruffs plexus: Most common site for posterior epistaxis Two arteries anastomose to form this area: 1. the sphenopalatine artery 2. Posterior ethmoid artery
- 3. Internal Nose Lymphatic Drainage Anterior 1/3 of the nose drains in to the submental and submandibular nodes Posterior two thirds of the nose and sinuses drain in to the retropharyngeal nodes and superior deep cervical nodes Nerve supply of the nose: by 3 cranial nerves CN I (olfactory nerve) Passes through the cribriform plate of the ethmoid bone into the olfactory bulb lying in the anterior cranial fossa Carries the sense of smell from the olfactory mucosa in the roof of the nose CN V (trigeminal nerve) Through ethmoidal branches of the ophthalmic division of CN V:Responsible for sensory innervation to: The lining of the anterior part of the nasal cavity To the surrounding olfactory mucosa in the roof of the nose To the lining of the frontal sinus Through Maxillary division of CN V:Responsible for sensory innervation to: The lateral wall of the nose The nasal septum The maxillary sinus CN VII (facial nerve|: Responsible for movement of external nose. Venous Drainage Venous system is valveless. Sphenopalatine vein drains via sphenopalatine foramen into pterygoid plexus. Ethmoidal veins drain into superior ophthalmic vein Anterior facial vein drains through common facial vein to internal jugular vein; also communicates with cavernous sinus via ophthalmic veins, infra orbital and deep facial veins, and the pterygoid plexus. Angular vein drains external nose via ophthalmic vein to cavernous sinus. Lymphatic Drainage Anterior portion of nose drains toward external nose in the subcutaneous tissue to the facial vein and submandibular nodes. Others pass posterior to tonsillar region and drain into upper deep cervical nodes. Most drain into pharyngeal plexus and then to the retropharyngeal nodes
- 4. Paranasal Sinuses The paranasal sinuses are air-filled spaces located within the bones of the skull and face and they are centered on the nasal cavity Includes 4 pairs one on each side: sphenoid, frontal, ethmoid, and maxillary All sinuses are lined with respiratory epithelium capable of producing mucus. The cilia in the sinus cavities help to empty secretions into the nasal cavities. Maxillary Sinus Present at birth Largest of the paranasal sinuses (15 ml its volume) Lateral wall of the nose separates the sinus from the nose Roof of the sinus is also the floor of the orbit Drains into the middle meatus of the nasal cavity Roots of the posterior molar teeth may extend into the floor of the sinus The anterior maxillary sinus wall houses the infraorbital nerve, which runs along the roof of the sinus and supplies sensory innervation to the lower eyelid, the side of the nose, and the upper lip. Ethmoidal sinus Paired bony scaffolds, connected by cribriformplate Boundaries: Lamina papyracea of orbit Orbital process of the frontal bone Middle and superior turbinates medially Lateral cribriform plate lamella (also medially) Sphenoid sinus posterioriy Nerve supply: anterior and posterior ethmoidal nerves Blood supply: anterior and posterior ethmoidal arteries from the ophthalmic A. Ant. cells: drain into middle meatus, the Post. cells drain into superior meatus.
- 5. Frontal sinus:- . abscent at birth Occupy the frontal bone, 2 in number Relations: The floor of the frontal sinus corresponds to the roof of the orbit. The frontal sinus is defined anteriorly by the thicker anterior table of the frontal bone and the thinner posterior table which separates the frontal sinus from the anterior horns of the frontal lobes of the brain. The pneumatization patterns of the frontal sinus widely vary. An intersinus septation generally divides the sinus, albeit asymmetrically. 5-15% of adults, the frontal sinus is completely aplastic. The frontal sinus ostium opens inferiorly into middle meatus Sphenoid Sinus Occupies sphenoid bone, 2 in number separated by Intersinus septum (not usually midline) Post-ethmoid A and N give vascular and sensory supplies, respectively Ostium ~1 cm above choana, and drains into sphenoethmoidal recess Relations: 1. Pituitary fossa and middle cranial fossa superiorly 2. Cavernous sinus and ICA laterally 3. Pons and posterior cranial fossa posteriorly 4. Optic nerve lies next to or even within the sinus 5. Pterygoid canal with nerve inferiorly. Sphenoid sinus forms the roof of nasopharynx. Ostiomeatal Complex (OMC) Area that drains the frontal, anterior ethmoid, and maxillary sinuses. The OMC drains into the middle meatus and then into the nasopharynx Functions of the Nose Airway: conduit for air Filtration: trap and remove airborne particulate matter Humidification: increases relative humidity Heating: provides radiant heat of inspired air Nasal reflex: causes periodic nasal congestion, rhinorrhea, or sneezing A. Postural reflex: increased congestion with supine position; congestion on the side of dependence upon lying on the side B. Hot or cold temperature reflex: sneezing upon sudden exposure of skin to dramatic temperature extremes Chemosensation: detects irritants and temperature changes Olfaction
- 6. Functions of paranasal sinuses The following are the possible functions of paranasal sinuses: Imparting resonance to the voice. Humidification and warming of inspired air. Increasing the olfactory area of nose. Providing thermal insulation to vital parts of head. Shock absorber function. Aiding facial growth: frontal and maxillary sinuses were designed to assist forward and downward growth of the face. Lightening the skull bones to maintain head position. Secreting mucous to moisten the nasal cavity. Aiding nasal cavity immune defense and production of nitric oxide. CONGENITAL ANOMALIES CHOANAL ATRESIA Choanal atresia (CA) is a rare congenital disorder where the back of the nasal passage (choana) is blocked, usually by abnormal bony or soft tissue. Although it is rare, it is the most common cause of nasal obstruction in neonates and young infants. It can be unilateral or bilateral. When it is bilateral, it can cause immediate respiratory compromise in the newborn and is considered a medical emergency. The diagnosis can be made on physical examination by trying to pass a small catheter through the patients nose. Surgery is the treatment of choice. Congenital Midline masses include 1. Dermoid cyst 2. Glioma 3. Encephalocele: Congenital herniation of central nervous system (CNS) tissue through skull base