It is located posteriorly to the inferior concha of the nasal cavity. The pharyngeal orifice marks the opening of the Eustachian tube into the nasopharynx. The cartilaginous part is incomplete along the lower and lateral margin of the tube, and is completed by fibrous tissue – the membranous lamina. It lies in a groove between the petrous part of the temporal bone and the greater wing of the sphenoid bone (petrosphenoidal fissure). The cartilaginous portion refers to the two-thirds of the Eustachian tube nearest to the nasopharynx. It has a serrated margin for attachment of the cartilaginous component of the tube. The distal end of the osseous portion is formed by the petrous part of the temporal bone. It can be variably surrounded by peritubal air cells.Īlong the roof of the osseous part of the Eustachian tube is a canal containing the tensor tympani muscle. The osseous portion refers to the third of the Eustachian tube nearest to the middle ear. Note the proximity of the internal carotid artery to the auditory orifice, Osseous Portion This fluid motion is detected by the hair cells, which then send nerve impulses about the position of your head and body to the brain to allow you to maintain your balance.Adobe Stock, Licensed to TeachMeSeries Ltdįig 2 – The osseous and cartilaginous parts of the Eustachian tube. When you move your head, the fluid within the semicircular canals (which sit at right angles to each other) also moves. The semicircular canals also contain fluid and hair cells, but these hair cells are responsible for detecting movement rather than sound. It helps dampen the vibrations in the cochlea. The round window (fenestra cochlea) is a membrane that connects the cochlea with the middle ear. The hair cells then convert these vibrations into nerve impulses, or signals, which are sent via the auditory nerve to the brain, where they are interpreted as sound. The vibrations transmitted from the middle ear cause tiny waves to form in the inner ear fluid, which make the cilia vibrate. The cochlea is filled with fluid and contains the organ of Corti - a structure that contains thousands of specialised sensory hair cells with projections called cilia. The inner ear (also called the labyrinth) contains 2 main structures - the cochlea, which is involved in hearing, and the vestibular system (consisting of the 3 semicircular canals, saccule and utricle), which is responsible for maintaining balance. By swallowing or ‘popping’ your ears, you can equalise the pressure. This can make your ear drum bulge or retract and less able to transmit vibrations, causing temporary hearing problems. during take off and landing when travelling on a plane), the pressure in the middle ear is not the same as the outside air pressure. In situations when there is a sudden change in air pressure (e.g. When you swallow, your Eustachian tube opens up to allow air into the middle ear, so that the air pressure on either side of the tympanic membrane is the same. Its function is to allow air into the middle ear as well as drain mucus from the middle ear into the nasopharynx. The Eustachian tube is a narrow tube that connects your middle ear to the back of your nose and throat (known as the nasopharynx). This vibration is then transmitted to the ossicles, which amplify the sound and pass on the vibration to the oval window (a thin membrane between the middle and inner ear). Sound waves that reach the tympanic membrane cause it to vibrate. The middle ear is an air-filled space that contains 3 tiny bones (known as ossicles), called the malleus (hammer), incus and stapes (stirrup).
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