Anatomy - Ear Flashcards
Auricle / Pinna (OE)
The outermost or external ear is the Pinna. It comprises a thin plate of elastic cartilage covered by a layer of skin.
It consists of funnel-like curves that helps collect sound waves travelling through the air and directs them into the external auditory canal.
External Auditory Canal (OE)
It is a slightly curved canal supported by bone in its interior part and cartilage in its exterior part. It also has wax glands. As sound waves enter through the auditory canal, they change the pressure on the ear drum.
Within our complex hearing pathway, the ear canal is responsible for funnelling sound waves toward the tympanic membrane (ear drum) and into the middle ear, and as such is a physical link between the tympanic membrane and the outside world.
Tympanic membrane / Eardrum (ME)
Semitransparent membrane covered by a layer of skin on its outer surface and a membrane inside. This membrane separates the middle ear and the external ear.
Similar to the membrane on a drum, the tympanic membrane vibrates as it encounters sound. It then transmits these vibrations to the ossicles of the middle ear to be further passed on to the cochlea of the inner ear for transduction
Tympanic Cavity (ME)
It is a narrow air-filled cavity separated from the external ear by the tympanic membrane and from the inner ear by the bony wall. Its main function is to separate the outer ear from the middle ear.
The tympanic cavity has an auditory tube known as the Eustachian/Auditory tube in its anterior wall.
Auditory / Eustachian Tube (ME - T)
The eustachian tube connects the middle ear to the back of the throat. It helps maintain equal pressure on both sides of the ear drum. Function is noticeable during rapid altitude changes.
Auditory Ossicles (ME)
They are tiny bones that transmit vibrations between ear drum and inner ear. They are responsible for transmitting sound waves from the ear drum to the middle ear.
They help amplify the force of vibrations from the ear drum to the oval window.
Auditory Ossicles (P)
- Malleus: A hammer shaped part that is attached to the tympanic membrane through the handle and incus through the head. It is the largest ear ossicle.
- Incus: An anvil shaped ear ossicle connected with the stapes.
- Stapes: It is the smallest ossicle and also the smallest bone in the human body, and it is stirrup shaped.
Semicircular Canals (IE)
Located in the inner ear, the semicircular canals are three very small tubes whose primary job is to regulate balance and sense head position.
The semicircular canals of each ear contain three main parts: anterior, posterior, and horizontal canals. Each of these canals provides a separate sense of directional balance, and each canal on the left is always paired with a canal on the right for normal function.
Vestibule (IE)
The vestibule is located within the inner ear. It is connected to the stapes via the oval window and is found between the cochlea and semicircular canals.
The function of the vestibule is to detect movement and acceleration of the body. The information provided by the vestibule helps the body to maintain balance.
Cochlea
The cochlea is a hollow, spiral-shaped bone found in the inner ear that plays a key role in the sense of hearing and participates in the process of auditory transduction.
It converts the auditory signals to neural impulses, which are carried by the afferent nerves fibres and auditory nerves to the brain, where it is integrated and we hear the sound.
Sound Travel
- Sound Waves are received by the external auditory canal.
- The Eardrum vibrates
- Malleus, Incus & Stapes amplify the vibrations.
- Vibration reaches the inner ear through the Oval Window.
- Movement of Fluid by pressure waves.
- Hair cells of Organ of Corti get stimulated by the vibration in the basilar membrane.
- Auditory Nerve transmits impulses to the brain.
