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Questions and Answers
Which part of the ear is an air-filled space?
Which nerve innervates the cranial surface of the auricle?
Which artery supplies blood to the external ear?
Where are the ceruminous glands located?
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Which nerve innervates the external acoustic meatus?
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What is the composition of the bony part of the external acoustic meatus?
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What type of hearing loss is associated with obstruction, otosclerosis, and otitis media?
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Which disease is characterized by vertigo, hearing loss, and tinnitus, and mostly begins after the age of 40?
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What is the longest human osseous canal of a nerve, running from internal acoustic meatus to stylomastoid foramen?
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Which nerve contains sensory and parasympathetic fibers of the facial nerve and joins with the motor root at the geniculate ganglion?
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Which part of the temporal bone has been partly sectioned in the illustration?
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What type of loss is associated with damage to the cochlea and CN VIII?
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Which structure within the inner ear is responsible for converting sound stimuli into electrical signals?
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Which component of the Vestibulocochlear Nerve (CN VIII) is responsible for balance?
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Where do sound waves travel to after passing through the external auditory canal?
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Which part of the inner ear contains a semicircular duct and connects with the vestibule?
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Where does the Vestibulocochlear Nerve (CN VIII) enter the inner ear?
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What is the function of the Vestibular System efferent fibers?
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What is the function of the middle ear?
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Which nerve innervates the external surface of the tympanic membrane?
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What is the shape of the stapes bone?
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Which muscle inserts into the manubrium of the malleus?
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What is the function of the Eustachian Tube?
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What is the bony part of the Eustachian Tube called?
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Which structure separates the middle ear from the jugular fossa?
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What does the tympanic plexus innervate within the tympanic cavity?
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Which structure contains the oval window and round window through which sound waves enter the inner ear?
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Where is the vestibular membrane located?
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What connects the perilymph and the subarachnoid space?
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Where are the saccule and utricle located?
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Study Notes
- The human ear's tympanic cavity is shaped like a narrow box with concave sides, and is separated from the middle cranial fossa by the tegmental wall.
- The jugular wall, or fundus tympani, is a thin layer of bone that separates the middle ear from the jugular fossa. The superior bulb of the internal jugular vein rests beneath the internal aperture of the tympanic canal, where the tympanic nerve (glossopharyngeal nerve) passes.
- The tegmental wall, or tegmen tympani, is a thin bone layer formed by the petrous part of the temporal bone and is the roof of the tympanic cavity. It separates the middle ear from the middle cranial fossa and forms part of the floor of the lateral part of the middle cranial fossa. Apertures for veins passing into the superior petrosal sinus are present in the tegmental wall, which has clinical correlates for middle ear infections spreading to the meninges.
- The medial wall of the tympanic cavity, also known as the labyrinthine cavity, separates the tympanic cavity from the inner ear. The promontory of the labyrinthine wall is formed by the initial part (basal turn) of the cochlea, and it contains the oval window and round window through which sound waves enter the inner ear. The tympanic plexus runs over the promontory, while the facial canal and cochlear canaliculus are located near the round window.
- The lateral wall of the tympanic cavity, also known as the membranous labyrinth, is formed almost entirely by the peaked convexity of the tympanic membrane. The superior part is formed by the lateral bony wall of the epitympanic recess, and the petrotympanic fissure (Glasserian fissure, squamotympanic fissure) runs from the tympanomastoid joint to the tympanic cavity, dividing the mandibular fossa into two and allowing the passage of the chorda tympani and anterior tympanic artery.
- The posterior wall of the tympanic cavity, also known as the mastoid wall, is wider superiorly than inferiously. The entrance to the mastoid air cells, or aditus, is located on the mastoid wall, which also contains the pyramidal eminence, where the stapedius muscle is located. The Eustachian tube connects the middle ear to the nasopharynx, allowing the equalization of air pressure.
- The human ear's innervation includes the tympanic plexus, which innervates the mucosa lining the walls and contents of the tympanic cavity. The lesser petrosal nerve, a branch of the tympanic nerve, supplies preganglionic parasympathetic fibers to the otic ganglion.
- The inner ear consists of the vestibulocochlear organ, which conveys information to the brain about balance and hearing. It is divided into the bony labyrinth and the membranous labyrinth. The bony labyrinth is a series of bony cavities within the petrous part of the temporal bone and is composed of the cochlea, vestibule, and three semi-circular canals. The membranous labyrinth is continuous with the bony labyrinth and is composed of the cochlear duct, semicircular ducts, and the saccule and utricle, which are organs of balance.
- The cochlea is a part of the inner ear and is composed of the modiolus, spiral lamina, and the cochlear duct. The cochlear duct creates two canals, scalia vestibuli and scalia tympani, which separate at the helicotrema. The spiral organ is located on the basilar membrane, and the cochlear duct's outer wall is covered by the spiral ligament. The cochlear duct's roof is the vestibular membrane, which separates the endolymph in the cochlear duct from the perilymph in the scala vestibuli.
- The cochlear canaliculus is a small channel near the round window that passes through the temporal bone and opens into the postcranial fossa, connecting the perilymph and the subarachnoid space.
- The vestibule is the central part of the bony labyrinth, separated from the middle ear by the oval window and communicating anteriorly with the cochlea and posteriorly with the semi-circular canals. It is lined internally with periosteum and contains perilymph, which is similar to cerebrospinal fluid.
- The membranous labyrinth is divided into two parts, the saccule and utricle, and is located within the vestibule. It is a continuous system of ducts filled with endolymph and consists of the cochlear duct, semicircular ducts, and the organs of balance, the saccule and utricle.
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Description
Test your knowledge of ear anatomy and factors contributing to acute otitis media development. Identify key structures of the tympanic cavity and understand the difference in angle to horizontal axis between children and adults.
