Human hearing organs {ear} have outer ear to catch sounds, middle ear to concentrate sounds, and inner ear to analyze sound frequency and intensity.
Pinna and ear canal {outer ear}| gather and focus sound on eardrum.
Only mammal ears have a cartilage flap {pinna}| {pinnae}, to catch sounds.
A 2.5-centimeter tube {auditory canal}| {ear canal}, from outside pinna to inside tympanic membrane, protects tympanic membrane from objects and loud sounds.
Auditory canal has wax {earwax}|. Perhaps, earwax keeps ear canal moist and/or sticks to insects.
Thin connective-tissue membrane {tympanic membrane} {eardrum}| is across ear-canal inner end. Tympanic membrane is 18 times larger than oval window.
Eardrum connects to air cavity {middle ear}|.
Middle ear has three small bones {ossicles}|: hammer, anvil, and stirrup. Two middle ear bones evolved from reptile lower jawbones [Ramachandran, 2004].
Eardrum connects to middle-ear bone {hammer bone}| {malleus}, which connects to anvil.
Hammer bone connects to middle-ear bone {anvil bone}| {incus}, which connects to stirrup. Anvil bone is smaller than hammer bone to concentrate sound pressure.
Anvil bone connects to middle-ear bone {stirrup bone}| {stapes}, which connects to oval window. Stirrup bone is smaller than anvil bone to concentrate sound pressure.
Muscles {tensor tympani muscle} attached to malleus can tense to dampen loud vibration.
Muscles {stapedius muscle} attached to stapes can tense to dampen loud vibration.
1-Consciousness-Sense-Hearing-Anatomy
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Date Modified: 2022.0225