Anatomy of the Ear Flashcards
What are the three regions of the ear?
The ear is divided into three regions: the external or outer ear, the middle ear, and the inner or internal ear. Each region has a role in hearing, but only the inner ear is associated with the vestibular sense, which is important to equilibrium.
What is the function of the auricle (pinna) in the outer ear?
The auricle, or pinna, is made of elastic cartilage, with the exception of the fleshy lobule, and is covered with skin. It funnels sound waves into the external auditory canal.
What is the role of the external auditory canal?
The external auditory canal is a slightly curved tunnel through the temporal bone that terminates at the tympanic membrane. It is lined with modified sweat glands, known as ceruminous glands, which secrete cerumen, or ear wax. This waxy substance lubricates and waterproofs the canal and tympanic membrane, and traps and removes debris before it reaches the tympanic membrane.
What is the tympanic membrane and what is its function?
The tympanic membrane is a thin sheet of epithelium and connective tissue that separates the outer and middle ear regions. It is cone-shaped with its apex or tip pointing into the middle ear and is connected to a tiny bone, or ossicle. The tympanic membrane enables the energy of sound waves to reach the inner ear.
What is the function of the pharyngotympanic tube in the middle ear?
The pharyngotympanic tube, also known as the auditory tube, connects the nasopharynx with the middle ear. It equalizes air pressure on both sides of the tympanic membrane. Pressure differences between the chambers reduce the ability of the tympanic membrane to accurately vibrate, which negatively affects hearing.
What are the auditory ossicles and what is their role in hearing?
The auditory ossicles are three tiny bones within the middle ear, named by their shapes: the malleus, incus, and stapes. They are connected to one another at synovial joints and form a bridge that links the tympanic membrane to the outer wall of the inner ear. The ossicles amplify and convert incoming sound waves in air into fluid movement.
What are the two tiny skeletal muscles attached to the ossicles and what is their function?
What are the two tiny skeletal muscles attached to the ossicles and what is their function?
What is otitis media?
Otitis media is an inflammation of the middle ear cavity. It is one of the most common infections in children and is almost always preceded by an upper respiratory infection. Common symptoms include ear pain, fever, impaired hearing, irritability, and in some cases, vomiting.
What is acute otitis media (AOM) and how does it affect hearing?
Acute otitis media (AOM) occurs when the pharyngotympanic tube acts as a conduit for pathogens in the nasopharynx to reach the middle ear. The resulting inflammation causes a buildup of fluid or pus, causing the tympanic membrane to bulge painfully into the auditory canal, which interferes with hearing.
Why are children more susceptible to AOM?
Children are more susceptible to AOM because their pharyngotympanic tubes are much shorter and more horizontal than in adults. Additionally, they have more frequent upper respiratory infections because their immune systems are immature.
What is otitis media with effusion (OME) and how is it treated?
Even with treatment, AOM can progress to otitis media with effusion (OME), where the infection has cleared but fluid remains, interfering with the movement of the tympanic membrane for normal hearing. Persistent OME can be treated with a myringotomy, where a small hole is pierced in the tympanic membrane to drain the middle ear. A small tube may be inserted into the hole to prevent the infection from recurring.
What are the three regions of the inner ear?
The inner ear is a cavity within the temporal bone and is subdivided into three regions: the cochlea, vestibule, and semicircular canals
What are the bony and membranous labyrinths in the inner ear?
The bony labyrinth consists of open passageways that make up the inner ear chamber, while the membranous labyrinth is made up of membranes that line the bony labyrinth and contain endolymph. Both the bony and membranous labyrinths form a network of serpentine pathways.
What is the role of endolymph and perilymph in the inner ear?
Endolymph is a fluid in which the potassium ion concentration is greater than the sodium ion concentration, making it similar to intracellular fluid. Perilymph is a fluid between the bony and membranous labyrinths, where the sodium ion concentration is greater than the potassium ion concentration, making it similar to extracellular fluid. Both fluids play a role in transducing sound waves and head movements into electrical signals.
What is the function of the vestibule in the inner ear?
The vestibule is located medially to the middle ear and its wall features a membranous oval window. It houses the utricle and saccule, two parts of the membranous labyrinth that are endolymph-filled chambers containing receptor cells. These cells convey stimuli about head tilting and linear movement via neurons of the vestibular division of the vestibulocochlear nerve (CN VIII).
