The malleus, attached to the tympanic membrane, and the serially connected incus and stapes begin vibrating. Sound waves travel through the external auditory canal, strike the tympanic membrane, and cause it to vibrate. Hearing is the interpretation of sound waves by the brain. Equilibrium receptors in the semicircular canals and vestibule of the inner ear respond to changes in direction of movement and send signals to the cerebellum to maintain balance. The semicircular canals contain the end organs for vestibular function. The cochlea, a coiled structure containing the organ of Corti, transmits sound impulses to the eighth cranial nerve. The inner ear is a membranous, curved cavity inside a bony labyrinth consisting of the vestibule, semicircular canals, and cochlea. The equalized pressure in the middle ear permits the tympanic membrane to vibrate freely with sound waves. Muscles briefly open this passage (during swallowing, yawning, or sneezing) to clear middle ear secretions and to equalize the middle ear pressure with atmospheric pressure. The eustachian tube drains into the posterior aspect of the inferior turbinate of the nose. The middle ear mucosa produces a small amount of mucus that is rapidly cleared by the ciliary action of the eustachian tube, a cartilaginous, fibrous, and bony passageway between the nasopharynx and the middle ear. Structural landmarks of the right tympanic membrane in relation to a clock face. Most of the tympanic membrane is tense (the pars tensa), but the superior portion (pars flaccida) is more flaccid ( Fig. Its oblique position to the auditory canal and conical shape account for the triangular light reflex. The tympanic membrane is translucent, permitting the middle ear cavity and malleus to be visualized. It is concave, being pulled in at the center (umbo) by the malleus. The tympanic membrane, surrounded by a dense fibrous ring (annulus), separates the external ear from the middle ear. The air-filled cells of the mastoid area of the temporal bone are continuous with the middle ear. It contains the ossicles, three small connected bones (malleus, incus, and stapes) that transmit sound from the tympanic membrane to the oval window of the inner ear. The middle ear is an air-filled cavity in the temporal bone. Cerumen provides an acidic pH environment that inhibits the growth of microorganisms. This canal lining is protected and lubricated with cerumen, secreted by the apocrine glands in the distal third of the canal. Its skeleton of bone and cartilage is covered with thin, sensitive skin. The external auditory canal, an S-shaped pathway leading to the middle ear, is approximately 2.5 cm (1 in) long in adults. The lobule is the soft lobe on the bottom of the auricle. The tragus is the protuberance lying anterior to the auditory canal meatus, and the antitragus is the protuberance on the antihelix opposite the tragus. The concha is the deep cavity containing the auditory canal meatus. The helix is the prominent outer rim, whereas the antihelix is the area parallel and anterior to the helix. Inspect the oropharyngeal characteristics of the tonsils and posterior wall of the pharynx. Inspect the tongue for color, symmetry, swelling, and ulcerations.Īssess the function of cranial nerve XII (hypoglossal).Įlicit the gag reflex (cranial nerves IX and X). Inspect and palpate the gingivae and buccal mucosa for color, lesions, and tenderness. Inspect and palpate the lips for symmetry, color, and edema. Palpate the frontal and maxillary sinuses for the tenderness or pain, and swelling. Inspect the frontal and maxillary sinus area for swelling. Inspect the nasal mucosa and nasal septum for: Palpate the bridge and soft tissues of the nose, noting: Inspect the external nose, noting the shape, size, color, and nares. Inspect the auditory canal with an otoscope, noting: Palpate the auricles and mastoid area for tenderness, swelling, and nodules. Inspect the auricles and surrounding area for:
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