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The Ear

The Ear. Damaris Alas Lusine Zhamharyan Matt Marquez Period 3. Ear Structure. Made up of three parts Outer ear (external) Middle ear Inner ear. Outer (External) Ear. Pinna ( outer ear cartilage) External Auditory Canal

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The Ear

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  1. The Ear Damaris Alas Lusine Zhamharyan Matt Marquez Period 3

  2. Ear Structure • Made up of three parts • Outer ear (external) • Middle ear • Inner ear

  3. Outer (External) Ear • Pinna (outer ear cartilage) • External Auditory Canal • Lined with hairs and ceruminous glands, which prevent objects and insects from entering. • Both funnel sound waves towards the tympanic membrane (eardrum), causing it to vibrate.

  4. Middle Ear (Tympanic Cavity) • Air filled space located in the temporal bone of the skull • Contains 3 small auditory bones: • Malleus • Incus • Stapes • Auditory Tube • Drains fluid • Adjusts ear pressure

  5. Middle Ear Ossicles • Inter-articulated bones of the middle ear that amplify the vibration of the eardrum and send them to the internal ear • Attached by ligaments • Malleus attached to ear drum • Stapes attached to oval window of inner ear

  6. Middle Ear… Adjusting Ear Pressure • The auditory tube maintains equal pressure in the ear • Does this by: • Draining fluid from the middle ear into the throat • Allows the air to pass between the tympanic cavity and the outside of the body by way of the throat and mouth

  7. Middle Ear… Protective Mechanism • Tympanic Reflex • Involuntary muscle contractions after loud sounds • Ossicles are pulled on causing them to become more rigid and less effective • Vibrations are dampened

  8. Inner Ear • Composed of a labyrinth • Osseous Labyrinth (Bony) • Secretes Perilymph • Membranous Labyrinth • Lies within the osseous • Contains Endolymph • Main Structures: • Cochlea • Semicircular Canals • Vestibule

  9. Inner Ear … Cochlea • Shaped like a snail shell • Bony labyrinth is divided in two • Upper: ScalaVestibuli • Oval Window to the apex • Vestibular Membrane • Lower: Scala Tympani • Apex to the round window • Basilar Membrane • Both connected by helicotrema • Membranous labyrinth lies in the middle, called the Scala Media (cochlear duct)

  10. Inner Ear … Cochlea

  11. Inner Ear … Cochlea (cont.) • Houses the organ of Corti • 16,000 hearing receptor hair cells • Lies on the upper surface of the basilar membrane • Hair cells extend into the cochlear duct

  12. Auditory Nerve Pathway • Carries the signal into the brainstem and synapses in the cochlear nucleus • From there the auditory information splits into motion and form procession • Auditory nerve fibers going to the ventral cochlear nucleus synapse on their target cells with giant, hand like terminals • Two streams: • Cells project to a collection of nuclei in the medulla called the superior olive

  13. Auditory Nerve • Vestibulocochlear • located in the internal auditory canal • responsible for both hearing and balance and brings information from the inner ear to the brain • Two special organs help the nerve function properly: • cochlea and vestibular apparatus

  14. Equilibrium • Comes from 2senses: • Static Equilibrium • Senses position of the head • Maintains stability and posture • Dynamic Equilibrium • Senses motion • Aids in maintaining balance

  15. Static Equilibrium • Comes from: • Utricle and Saccule in Vestibule • Contain Macula • Hair cells which act as sensory receptors • Covered in layer of a gelatinous matrix • Otoliths embedded on surface • Weigh down on membrane making it more responsive to changes

  16. Static Equilibrium

  17. Dynamic Equilibrium • Comes from: • Ampullae in semicircular canals • Communicate with the utricle • Contain Crista Ampullaris • Also contains hair cells that extend into a gelatinous matrix (cupula)

  18. Dynamic Equilibrium

  19. Sound Wave Pathway

  20. Sound Wave Pathway

  21. Deafness • Can be: • Acquired • Picked up, and caused by outside factor • Exposed to intense, pure tone • Inherited • Born with • More than 100 types • One in a thousand newborn are deaf because of genetic defects • 2 Types: • Sensorineural • Damage to the cochlea or auditory nerve • Conductive: • Interference with transmission of vibrations in inner ear

  22. Work Cited "Auditory and Vestibular Pathways." Bioon. Web. 31 Mar. 2014. <http://www.bioon.com/bioline/neurosci/course/audvest.html>. "Auditory Tube - Ear." Inner Body. Human Anatomy. Web. 31 Mar. 2014. <http://www.innerbody.com/image_nerv13/nerv128-new.html>. "Ear Anatomy." Enchanted Learning. Web. 31 Mar. 2014. <http://www.enchantedlearning.com/subjects/anatomy/ear/>. "The Human Ear." Biology of Humans. Pearson, Web. 31 Mar. 2014. <http://wps.aw.com/bc_goodenough_boh_4/177/45511/11650899.cw/index.html>. "Structure of the Ear." Visual Meriam Dictionary. Meriam-Webster, Web. 31 Mar. 2014. <http://visual.merriam-webster.com/human-being/sense-organs/hearing/structure-ear.php>. Wedro, Benjamin C., M.D. "Hearing and Balance Anatomy." Ed. William C. Shiel, M.D. Medicine Net. Web. 31 Mar. 2014. <http://www.medicinenet.com/script/main/art.asp?articlekey=21685>.

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