Lecture 9 - Nose, Paranasal Sinuses, and Ear PDF

THE NOSE n n n The nose is the superior part of the respiratory tract and it contains the peripheral organ of smell. It is divided into a right and left cavities by the nasal septum. Each naris is divided into: n n Olfactory area (superior 1/3) Respiratory area (inferior 2/3) THE NOSE n FUNCTI...

THE NOSE n n n The nose is the superior part of the respiratory tract and it contains the peripheral organ of smell. It is divided into a right and left cavities by the nasal septum. Each naris is divided into: n n Olfactory area (superior 1/3) Respiratory area (inferior 2/3) THE NOSE n FUNCTIONS: 1. 2. 3. 4. 5. Respiration Olfaction Filtration of dust and other particles Humidification of inspired air Reception of secretions from the paranasal sinuses and nasolacrimal ducts. External Nose (Naris) n n Bridge Two nostrils bounded medially by the nasal septum and laterally by the ala of the nose. Nasal Septum n n n It is a bony/cartilagenous structure. The bony part is usually located in the median plane until age 7 years, it then deviates laterally to the right. The nasal septum has three separate components: The perpendicular plate of the ethmoid bone n The vomer n The septal cartilage n Nasal Cavities n n n n They extend from the nostrils anteriorly to the choanae posteriorly where they open into the nasopharynx. They are lined by mucous membranes adhered firmly to the periosteum and perichondrium EXCEPT the vestibule which is lined by skin covered with fine hairs. The inferior 2/3 of the nasal mucosa = respiratory area. The superior 1/3 = olfactory area n Olfactory receptor cells cribiform plate (ethmoid) olfactory nerves CN I Nasal Cavity - OPENINGS n n n n n n n Nostrils The choanae Maxillary, frontal, sphenoid, ethmoidal sinuses Nasolacrimal ducts Sphenopalatine foramen Incisive canal In the dry skull Cribiform plate Nasal Cavity - WALLS n n n n FLOOR: palatine processes of the maxilla and palatine bone ROOF: nasal cartilage, cribiform plate, sphenoid bone MEDIAL: nasal septum LATERAL: it is uneven due to three characteristic elevations: CONCHA or TURBINATES Nasal Cavity – CONCHA AND MEATUS n CONCHA: Superior Ethmoid bone n Middle n Inferior - Separate bone n The concha define spaces: MEATUS Nasal Cavity – CONCHA AND MEATUS n SUPERIOR MEATUS n n Below the superior concha Receives n n n n Above and behind the superior concha: sphenoethmoidal recess MIDDLE MEATUS n n Below the middle concha Receives n n n n Posterior ethmoidal sinuses Sphenoid sinus Maxillary sinus Frontal sinus (infundibulum) Anterior ethmoidal sinus INFERIOR MEATUS n n Below the inferior concha Receives the nasolacrimal duct Nasal Cavity – NERVE SUPPLY n n n n SYMPATHETIC: T1/SCG – blood flow regulation PARASYMPATHETIC: pterygopalatine ganglion – increase serous secretions OLFACTORY AREA: CN I RESPIRATORY AREA: CN V (V1 and V2 divisions) - sensory n n n n Anterior ethmoidal nerve (nasociliary n.) (V1) – anterior septum External nasal nerve (V1) – anterior septum Nasopalatine nerve (V2) – mucous membranes of nasal septum Nasal branches of V2 – lateral wall Nasal Cavity – BLOOD SUPPLY n n n n Maxillary artery through the sphenopalatine artery to supply the mucosa. The anterior and posterior ethmoidal arteries (ophthalmic a.) supply the anterosuperior part of the lateral wall. Superior labial (facial a.) ascending palatine, and lateral nasal. Kisselbach’s plexus is an area (Little’s area) in the anterior-inferior part of the nasal septum where the following arteries anastomose: n n n n Anterior ethmoidal artery (ophthalmic) Sphenopalatine artery (maxillary) Greaer palatine artery (maxillary) Septal branch of the superior labial artery (facial) PARANASAL SINUSES n They are air-filled extensions of the respiratory part of the nasal cavity into the following cranial bones: n FRONTAL n n n It’s superior It drains into the middle nasal meatus via the infundibulum ETHMOIDAL n It’s medial n n n n SPHENOIDAL n n n POSTERIOR ETHMOIDAL n Superior nasal meatus ANTERIOR ETHMOIDAL Middle nasal meatus It’s posterior It drains into the superior nasal meatus MAXILLARY n n It’s inferior It drains into the middle nasal meatus n n n n n n n n n The biological role of the sinuses is debated, but several possible functions have been proposed: Decreasing the relative weight of the front of the skull, and especially the bones of the face. Increasing resonance of the voice. Providing a buffer against blows to the face. Insulating sensitive structures like dental roots and eyes from rapid temperature fluctuations in the nasal cavity. Humidifying and heating of inhaled air because of slow air turnover in this region. Regulation of intranasal and serum gas pressures Immunological defense No function at all THE EAR n n It is the vestibulocochlear organ concerned with hearing, balance and equilibrium. It has three parts: EXTERNAL EAR n MIDDLE EAR n INTERNAL EAR n External Ear n n n It consists of the auricle and external auditory meatus (canal). The auricle (pinna) is a single elastic cartilage covered with skin. The external auditory canal measures approximately 2.5 cm with a cartilagenous lateral wall and a bony medial wall. n INNERVATION: n n n Auriculotemporal n. (V3) Great auricular nerve (C2,3 – cervical plexus) BLOOD SUPPLY: n n Posterior auricular a. (ECA) Superficial temporal a. (ECA) Tympanic Membrane n n n n n It is an oval, thin, semitransparent structure at the medial end of the external acoustic canal. It is a partition between the external and middle ears. It is covered by very thin skin externally, and mucous membrane internally. It is concave toward the meatus with a central depression called the UMBO (malleus bone). From the umbo a bright area projects anteriorly and inferiorly (CONE OF LIGHT) (5 o’clock [R], 7 o’clock [L]) n INNERVATION: n n n Auriculotemporal n. (V3) – external surface CN X, IX, VII BLOOD SUPPLY: n n Deep auricular a. (Maxillary a.) – external surface Posterior auricular (ECA) and tympanic branch of the maxillary to the internal surface Middle Ear (Tympanic Cavity) n n It is a narrow cavity in the temporal bone connected anteriorly with the nasopharynx by the auditory tube (Eustachian tube). Posterosuperiorly the tympanic cavity connects with the mastoid air cells through the mastoid antrum. Tympanic Cavity - CONTENTS n Auditory ossicles: n n n n n n n n n Malleus Stapes Incus Stapedius muscle (CN VII) Tensor tympani muscles (CN V3) Chorda tympani (CNVII) – between the malleus and the incus Tympanic plexus (CN IX) The posterior wall has the pyramid which contains the stapedius muscle The medial wall has: n n Facial canal Oval window Ear Pressure Equalization n n n The middle ear is an air-filled chamber connected to the nasopharynx (anteriorly) via the Eustachian tube or, auditory tube, or pharyngotympanic tube. Normally, air moves through the Eustachian tube to equalize pressure. This is particularly important in situations where there is a sudden pressure change as in, for example, diving or ascending/descending during airplane travel. Ear Pressure Equalization n n As an airplane ascends, the pressure in the cabin decreases relative to the pressure in the middle ear. The Eustachian tube opens causing a “pop” and air is moved from the middle ear to the pharynx. This occurs every 500 ft. – 1000 ft. until the pressures equalize. n n As we descend, the pressure in the cabin increases which causes the tympanic membrane to bulge inwards towards the middle ear. In this case, when the Eustachian tube pops, air moves from the pharynx into the middle ear to equalize the pressure. Ear Pressure Equalization n The muscles associated with the function of the Eustachian tube causing it to “pop” and move air in/out are the: n n n Tensor veli palatini muscle (CN V3) Levator veli palatine muscle (CN X) Salpingopharingeus muscle (CN X) Inner Ear n n It contains the vestibulocochlear organ which is concerned with reception of sound and maintenance of balance. It is found in the petrosal part of the temporal bone. Vestibulocochlear Nerve (CN VIII) n n n n It leaves the brain stem between the pons and the medulla oblongata. It travels laterally with CN VII, and it enters the internal acoustic meatus. It does not exit the skull. It has: Vestibular fibers for equilibrium n Cochlear fibers (“hair cells”) for hearing n