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The Eustachian tube (/ j uː ˈ s t eɪ ʃ ən /), also called the auditory tube or pharyngotympanic tube, [1] is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately 35 mm (1.4 in) long and 3 mm (0.12 in) in diameter. [2]
The torus tubarius (or torus of the auditory tube) is an elevation of the mucous membrane of the nasal part of the pharynx formed by the underlying base of the cartilaginous portion of the Eustachian tube (auditory tube). The torus tubarius is situated behind the pharyngeal orifice of the auditory tube. [1]
The inner part of the spiracle, still connected to the pharynx, forms the eustachian tube. [7] In reptiles, birds, and early fossil tetrapods, there is a single auditory ossicle, the columella which is homologous with the stapes, or "stirrup" of mammals.
The middle ear also connects to the upper throat at the nasopharynx via the pharyngeal opening of the Eustachian tube. [3] [11] The three ossicles transmit sound from the outer ear to the inner ear. The malleus receives vibrations from sound pressure on the eardrum, where it is connected at its longest part (the manubrium or handle) by a ligament.
The sound waves enter the auditory canal, a deceptively simple tube. The ear canal amplifies sounds that are between 3 and 12 kHz . [ 1 ] The tympanic membrane , at the far end of the ear canal marks the beginning of the middle ear .
The auditory tube, which connects the middle ear to the pharynx, opens into the nasopharynx at the pharyngeal opening of the auditory tube. The opening and closing of the auditory tubes serves to equalize the barometric pressure in the middle ear with that of the ambient atmosphere. Details of torus tubarius
Since it is also attached to the lateral cartilaginous lamina of the pharyngotympanic tube (auditory tube or Eustachian tube), it assists in its opening during swallowing or yawning to allow air pressure to equalize between the tympanic cavity and the outside air.
It arises from the lower part of the cartilage of the Eustachian tube, [1] and inserts into the palatopharyngeus muscle by blending with its posterior fasciculus. It is innervated by vagus nerve (cranial nerve X) via the pharyngeal plexus. It raises the pharynx and larynx during deglutition (swallowing) and laterally draws the pharyngeal walls up.