PARTS OF AN EAR
● The ears performs two sensory functions, `color{violet}"hearing"` and `color{violet}"maintenance of body balance"`.
● Anatomically, the ear can be divided into three major sections called the `color{brown}"outer ear"`, the `color{brown}"middle ear"` and the `color{brown}"inner ear."`
● The outer ear consists of the `color{brown}"pinna"` and `color{brown}"external auditory meatus"` (canal).
● The pinna collects the `color{violet}"vibrations in the air"` which produce sound.
● The external auditory meatus leads inwards and extends up to the `color{brown}"tympanic membrane (the ear drum)"`.
● There are very `color{brown}"fine hairs"` and `color{brown}"wax-secreting sebaceous glands"` in the skin of the pinna and the meatus.
● The tympanic membrane is composed of `color{violet}"connective tissues"` covered with skin outside and with `color{violet}"mucus membrane"` inside.
● The middle ear contains `color{brown}"three ossicles"` called `color{violet}"malleus, incus and stapes"` which are attached to one another in a chain-like fashion.
● The malleus is attached to the `color{violet}"tympanic membrane"` and the stapes is attached to the `color{brown}"oval window"` of the cochlea.
● The ear ossicles increase the `color{violet}"efficiency of transmission"` of sound waves to the inner ear.
● An `color{brown}"Eustachian tube"` connects the middle ear cavity with the pharynx.
● The Eustachian tube helps in `color{violet}"equalising the pressures"` on either sides of the ear drum.
● The `color{violet}"fluid-filled inner ear"` called `color{brown}"labyrinth"` consists of two parts, the `color{brown}"bony and the membranous "`labyrinths.
● The bony labyrinth is a `color{violet}"series of channels"`.
● Inside these channels lies the `color{violet}"membranous labyrinth"`, which is surrounded by a fluid called `color{brown}"perilymph"`.
● The `color{violet}"membranous labyrinth"` is filled with a fluid called `color{brown}"endolymph"`.
● The `color{violet}"coiled portion"` of the labyrinth is called `color{brown}"cochlea"`.
● The membranes constituting cochlea, the `color{brown}"reissner’s and basilar,"` divide the surounding perilymph filled bony labyrinth into an `color{brown}"upper scala vestibuli"` and a `color{brown}"lower scala tympani."`
● The space within cochlea called `color{brown}"scala media"` is filled with `color{violet}"endolymph"`.
● At the `color{violet}"base of the cochlea"`, the `color{violet}"scala vestibuli"` ends at the oval window, while the `color{violet}"scala tympani"` terminates at the round window which opens to the middle ear.
● The `color{brown}"organ of corti"` is a structure located on the `color{violet}"basilar membrane"` which contains `color{brown}"hair cells"` that act as `color{brown}"auditory receptors"`.
● The `color{violet}"hair cells"` are present in rows on the `color{violet}"internal side"` of the organ of corti.
● The `color{violet}"basal end"` of the hair cell is in close contact with the `color{violet}"afferent nerve fibres"`.
● A large number of processes called `color{brown}"stereo cilia"` are projected from the apical part of each hair cell.
● Above the rows of the hair cells is a `color{violet}"thin elastic membrane"` called `color{brown}"tectorial membrane"`.
● The inner ear also contains a complex system called `color{brown}"vestibular apparatus"`, located above the cochlea.
● The vestibular apparatus is composed of `color{brown}"three semi-circular canals"` and the `color{brown}"otolith organ"` consisting
of the `color{brown}"saccule and utricle"`.
● Each semi-circular canal lies in a `color{violet}"different plane at right angles"` to each other.
● The `color{violet}"membranous canals"` are suspended in the `color{violet}"perilymph"` of the bony canals.
● The `color{violet}"base of canals is swollen"` and is called `color{brown}"ampulla"`, which contains a projecting ridge called `color{brown}"crista ampullaris"` which has hair cells.
● The `color{violet}"saccule and utricle"` contain a projecting ridge called `color{brown}"macula"`.
● The `color{violet}"crista and macula"` are the specific receptors of the `color{violet}"vestibular apparatus"` responsible for maintenance of `color{violet}"balance of the body and posture"`.
● Anatomically, the ear can be divided into three major sections called the `color{brown}"outer ear"`, the `color{brown}"middle ear"` and the `color{brown}"inner ear."`
● The outer ear consists of the `color{brown}"pinna"` and `color{brown}"external auditory meatus"` (canal).
● The pinna collects the `color{violet}"vibrations in the air"` which produce sound.
● The external auditory meatus leads inwards and extends up to the `color{brown}"tympanic membrane (the ear drum)"`.
● There are very `color{brown}"fine hairs"` and `color{brown}"wax-secreting sebaceous glands"` in the skin of the pinna and the meatus.
● The tympanic membrane is composed of `color{violet}"connective tissues"` covered with skin outside and with `color{violet}"mucus membrane"` inside.
● The middle ear contains `color{brown}"three ossicles"` called `color{violet}"malleus, incus and stapes"` which are attached to one another in a chain-like fashion.
● The malleus is attached to the `color{violet}"tympanic membrane"` and the stapes is attached to the `color{brown}"oval window"` of the cochlea.
● The ear ossicles increase the `color{violet}"efficiency of transmission"` of sound waves to the inner ear.
● An `color{brown}"Eustachian tube"` connects the middle ear cavity with the pharynx.
● The Eustachian tube helps in `color{violet}"equalising the pressures"` on either sides of the ear drum.
● The `color{violet}"fluid-filled inner ear"` called `color{brown}"labyrinth"` consists of two parts, the `color{brown}"bony and the membranous "`labyrinths.
● The bony labyrinth is a `color{violet}"series of channels"`.
● Inside these channels lies the `color{violet}"membranous labyrinth"`, which is surrounded by a fluid called `color{brown}"perilymph"`.
● The `color{violet}"membranous labyrinth"` is filled with a fluid called `color{brown}"endolymph"`.
● The `color{violet}"coiled portion"` of the labyrinth is called `color{brown}"cochlea"`.
● The membranes constituting cochlea, the `color{brown}"reissner’s and basilar,"` divide the surounding perilymph filled bony labyrinth into an `color{brown}"upper scala vestibuli"` and a `color{brown}"lower scala tympani."`
● The space within cochlea called `color{brown}"scala media"` is filled with `color{violet}"endolymph"`.
● At the `color{violet}"base of the cochlea"`, the `color{violet}"scala vestibuli"` ends at the oval window, while the `color{violet}"scala tympani"` terminates at the round window which opens to the middle ear.
● The `color{brown}"organ of corti"` is a structure located on the `color{violet}"basilar membrane"` which contains `color{brown}"hair cells"` that act as `color{brown}"auditory receptors"`.
● The `color{violet}"hair cells"` are present in rows on the `color{violet}"internal side"` of the organ of corti.
● The `color{violet}"basal end"` of the hair cell is in close contact with the `color{violet}"afferent nerve fibres"`.
● A large number of processes called `color{brown}"stereo cilia"` are projected from the apical part of each hair cell.
● Above the rows of the hair cells is a `color{violet}"thin elastic membrane"` called `color{brown}"tectorial membrane"`.
● The inner ear also contains a complex system called `color{brown}"vestibular apparatus"`, located above the cochlea.
● The vestibular apparatus is composed of `color{brown}"three semi-circular canals"` and the `color{brown}"otolith organ"` consisting
of the `color{brown}"saccule and utricle"`.
● Each semi-circular canal lies in a `color{violet}"different plane at right angles"` to each other.
● The `color{violet}"membranous canals"` are suspended in the `color{violet}"perilymph"` of the bony canals.
● The `color{violet}"base of canals is swollen"` and is called `color{brown}"ampulla"`, which contains a projecting ridge called `color{brown}"crista ampullaris"` which has hair cells.
● The `color{violet}"saccule and utricle"` contain a projecting ridge called `color{brown}"macula"`.
● The `color{violet}"crista and macula"` are the specific receptors of the `color{violet}"vestibular apparatus"` responsible for maintenance of `color{violet}"balance of the body and posture"`.
