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Cochlea

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This is a structural diagram of the cochlea showing how fluid is pushed at the oval window and bulges out of the round window.

The cochlea is a spiral shaped organ of the auditory system that forms much of the inner ear. It is shaped like a snail shell and is essential to hearing. Inside the cochlea is the organ of Corti. This structure is composed of highly specialized cells which translate sound vibrations into nerve impulses, which than are sent to the brain. Tiny hair-like strands (Cilia) line the organ of Corti and protrude into fluid. The cilia are moved by the vibrations that enter the ear and are than sent to the brain. [1]

Structure

Interior view of the cochlea. This image was created before 1858.

The bony structure of the cochlea located in the inner ear has a snail-like shape. Within this there are two fluids: endolymph and perilymph. These two fluids help with balance. The Organ of Corti is a sensory receptor located inside the cochlea. This organ contains hairs cells, which are the nerve receptors for hearing. Along with the organ of corti the cochlea has three different airway chambers: scala vestibule (Vestibular canal) , scala media (Median canal) and scala tympani (Tympanic canal). Also the basticular membrane, tectorial membrane and Reissner’s membrane run in between the airways. [2]. The cochlea is an amazing structure created by God and contains an elegant spiral structure that helps us process sound and detect pitches. Inside almost looks like a spiral ramp that you could climb. The Median canal contains the oragn of corti. This is where different sound waves transform into action potentials. Rows of hair cells within the organ of corti come into contact and overlap the tectorial membrane. The vestibular canal is located in the median canal between the periodic skull bone and the upper membrane. This canal is filled with perilymph fluid. And final the tympanic canal is also filled with perilymph fluid and is connected to the vestibular canal, located at the end of the cochlear duct. [3].

Function

The inner ear (Cochlea) is a part of the auditory system that connects to the CNS (Central Nervous System). It functions as the sensorineural receptor organ of the auditory system and converts acoustic waveforms into electrochemical stimulus’s. The inner ear can dictate the different sound stimulus’s of frequency, intensity, and temporal properties. Once the sound is dictated the information is transmitted to the CNS where further interpreting and processing take place. When sound waves travel through the cochlear canals the different sounds and stimulus are interpreted and processed by the CNS. [4].

Cochear Implant

This is a picture showing how a cochlear implant is placed inside a persons ear to helping them hear. Patients who are deaf do to the damage of their sensory hair cells benefit from this implant.

Cost

These implants are recently priced from $50,000-$100,000 or even more. There are several things however that determines the cost of the implant. Such things to consider are the surgery, hospital costs, physicians fees, medication used, operating room supplies, the devices itself, and programming the device for the first year. And even after all of that is completed there are other ongoing costs to consider. Such as batteries, cables, and repair costs if needed. A lot of money goes in to this procedure because of the dysfunctions of the cochlea. Hopefully the patient has good health insurance to cut the cost a little bit. [5].

Efficacy

Implants are placed into three different levels of efficiency: Very effective, partially effective, and not effective at all. Implants are not a cure for deafness but they do allow the individual some contact with the outside world. When the patient can have some introduction to sounds or vibrations, they remember those and it helps them with future communications. With children, these implants are very successful and a high percentage of positive feedback has been documented. Not all patients have success with this, but the majority does and that’s encouraging for doctors to continue with richer advances. [6]

Risks

As helpful as this device can be, there are some disadvantages that can also occur for this procedure. Some cases have included that the patients experienced weakness in their expressional muscles and the worst cases included disfiguration paralysis. Also damage to the middle and inner ear can occur; this affects the functioning of the vestibular system. Any hearing that could have originally occurred could be lost. It is possible that after surgery, the device could not function properly. Risks are higher in children than in adults, as reported by the FDA. [7]

Cochlear Nerve Function

The cochlear nerve is also referred to as the acoustic nerve, because it aids in the transportation of sound. This nerve is a sensory nerve that transfers auditory information from the inner ear (the cochlea) to the brain. There are many parts that aid in the enablement to hear effectively. This important nerve is only one of those necessary parts. The nerve begins its work when sound vibrations hit the eardrum (tympanic membrane). When these vibrations hit the eardrum the movement that is created is converted into electrical signals. These signals are then transported to cochlear nerve carriers which deliver the signals to the brain for interpretation. Unfortunately, the cochlear nerve is vulnerable to many different defects and diseases. These can cause damage to the nerve in the auditory system. And unfortunately the individual suffers hearing loss because of it. Although optional treatment is offered to patients affected by cochlear never dysfunctions. The most effective treatment for this is a Cochlear implant. These implants have proven to restore a significant portion of hearing loss. Most patients that receive this type of treatment have come back with positive results and can mostly hear again. [8]

This is showing a longitudinal close up picture of the cochlea. This picture was drawn by Henry Gray in 1918 and can be found in his book "Gray's Anatomy".

Video

Cochlea Model

References

  1. Saunders Comprehensive Veterinary Dictionary, Farlex. Cochlea. “The Free Dictionary” Web. 5-16-15.
  2. Action Center, ASHA. The Inner Ear. “American Speech-Langiage-Hearing Association”. Web. 3-11-15.
  3. Vista, Tutor. Ear-Structure. “TutorVista.com” Web. 3-11-15.
  4. Crawford, James V. Cochlear Function. “Medscape”. Web. 3-11-15.
  5. Gardener, Evelyn.[ http://cochlearimplanthelp.com/journey/insurance-and-cost-issues/ Insurance and cost issues]. “cochlear implant HELP”. Web. 5-3-15.
  6. Tubbergh, Marius van.[ http://www.signgenius.com/cochlear-implant/cochlear-implant-efficiency.shtml Cochlear Implant Efficency:]. “SignGenius.com”. Web. 5-3-15.
  7. Tubbergh, Marius van.[ http://www.signgenius.com/cochlear-implant/cochlear-implant-risks-and-disadvantages.shtml Cochlear Implant Risks and Disadvantages?]. “SignGenius.com”. Web. 5-3-15.
  8. Editorial Team, Healthline. Cochlear nerve. “Healthline”. Web. 5-16-15.