Pemeriksaan Sistem Pendengaran (Jumat, 16 Okt 20) (2).pptx

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1. The Ear

2. Ear Anatomy B est ways to evaluate: (1) high resolution CT scan (bone algorithm in axial and coronal planes), (2) high resolution T2-weighted MRI (axial and coronal planes). S tructures of ear divided into three main portions: external, middle, and inner.

3. External Ear consists of auricle and external auditory meatus. The external auditory meatus is a sound-conducting canal that terminates at the tympanic membrane of the middle ear.

4. CT

5. Middle Ear or tympanic cavity C onsists of tympanic membrane and three auditory ossicles (malleus, incus and stapes ). Air is conveyed from the nasopharynx to the tympanic cavity through the eustachian tube (auditory tube). The tympanic membrane transmits sound vibrations to the auditory ossicles. The auditory ossicles, which are suspended in the middle ear, conduct sound vibrations from the tympanic membrane to the oval window of the inner ear. The middle ear subdivided into: epitympanum , mesotympanum and hypotympanum .

6. Inner Ear or bony labyrinth Contains: vestibule and semicircular canals ( control equilibrium and balance), cochlea ( responsible for hearing). Two openings of the vestibule are the oval window for the footplate of the stapes and the vestibular aqueduct , which contains the endolymphatic duct. The semicircular canals are continuous with the vestibule and are easily identified because of their three separate passages (superior [anterior], posterior, and lateral) that are at right angles to each other. The three interconnected semicircular canals are lined with microscopic hairs called cilia and are filled with fluid known as endolymph. Every time the position of the head changes, the fluid moves against the cilia, creating a kind of motion sensor. This helps the brain create a sense of balance.

7. The cochlea is a spiral-shaped structure with a base that lies on the internal auditory canal. Located within the basilar turn of the cochlea is the round window, which allows the fluid of the inner ear to move slightly for propagation of sound waves and nerve impulses to be sent to the brain. Within the bony labyrinth is a complicated system of ducts called the membranous labyrinth, which is filled with endolymph, a fluid that helps with the propagation of sound waves . Extending from the vestibule is a slender endolymphatic duct that terminates as the endolymphatic sac .