Anatomy And Physiology

Anatomy Physiology



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Understanding how humans hear is a complex subject involving the fields of physiology, psychology and acoustics. But the structure of the ear in basics is very simple to understand.The ear, or organ of hearing, is divisible into three parts: the external ear, the middle ear or tympanic cavity, and the internal ear or labyrinth. But for our purposes, let us just say that the ear is divided the ear into External, Middle, and Internal Ear without getting too complicated. The External part of the ear (what you can see) is called the Penna. The Internal Ear starts with the Ear Canal. The ear canal is lined with hair follicles and glands that produce a waxy oil called cerumen. This protects the ear by trapping dust, microorganisms, and other foreign particles, preventing them from entering and damaging the ear. The wax usually makes its way to the opening of the ear where it falls out or is removed by washing. Sound enters the ear as a pressure wave of varying frequency (pitch) and amplitude (volume), where it reaches the Ear Drum (The tympanic membrane or "eardrum" receives vibrations traveling up the auditory canal), which is the beginning of the internal ear. The ear drum connects to 3 small bones called ossicles, which are the Hammer(Malleus), The Anvil(Incus),and the stirrup (Stapes-The smallest bone in the human body). The Hammer is connected to the eardrum and links to the Stirrup via the Anvil. The stirrup is attached to a small oval window at the entrance to the cochlear (the nerve center or 'inner ear'). The beating eardrum sends vibrations through the middle ear bones into the cochlear. The eardrum and the Hammer, Anvil, and Stirrup form the 'middle ear'. The cochlear is a tiny cavity formed within the cranium shaped like a snail shell, filled with a thick fluid and lined inside with thousands of microscopic hair cells / nerve endings. The traveling wave stimulates specific hair cells along the cochlear according to the frequency and amplitude of the continuous stream of sound signals, and triggers an electrical impulse that is sent to the brain via the auditory cortex, which is a nerve that carries electrical impulses from the ear. The semicircular canals, also part of the inner ear, are responsible for the dizzy sensation. Inside these canals are a thick fluid. These canals are lined with hairs. As we move our heads, the motion cause the liquid to move, bending the hairs. When we are dizzy, it is because although we are not spinning, the fluid in these semicircular canals are still moving the hairs.

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