THE SPECIAL SENSES ( THE EAR)

• The outer ear - Which conducts sound waves by displacements of air.
• The middle ear - Which conducts the sound through series of small bones
• The inner ear -Which conducts the sound through liquid and transforms its energy into an electrical impulse that can be transmitted to the brain
• the outermost structure of the ear is the visible portion, which is call the auricle or pinna
• The auricles are composed of folds of cartilage, covered with the skin that produces a waxy yellow substance called cerumen
• Cerumen - functions as a filter for the outer ear, trapping dust and other foreign substances and preventing them from entering internal structures.
• External auditory meatus, a tubular structure also know as the acoustic meatus or external ear canal.
• the tympanic membrane, a thin, circular membrane stretched across the end of the canal. It is the structure commonly referred to as the eardrum.
• three bones are known collectively as the ossicles: malleus, incus, and stapes
• Atmospheric pressure is conveyed to the middle ear by way of the eustachian tube an airway that connects the middle ear with the nose and throat.
• The inner ear consists of a series of fluid-filled passages known collectively as the labyrinth.
• The front portion, called the cochlea, is the part of the inner ear involved in hearing
• The rear portion, called the vestibular apparatus is the part of the inner ear involved in the maintenance of equilibrium and balance.
• Cochlea is a long, tightly wound tube that looks somewhat like a snail's shell
• The interior of the cochlea is divided lengthwise by a structure known as Basilar membrane
• • Embedded in the basilar membrane are the receptive cells of the inner ear, which are known as hair cells
• Hair cells extend from the basilar membrane, toward a second membrane known as the tectorial membrane
• Together, the basilar membrane, hair cells, and tectorial membrane are known as the organ of Corti
• The vestibular apparatus consists of three semicircular canals and two bulging structure known as the saccule and utricle
• specialized fluid called the endolymph
• The saccule and the utricle use similar mechanisms to generate information about the position of the body in relation to the force of the gravity. Both structures contain tiny stones known as otoliths
• Impulses generated by the hair cells in the inner ear and vestibular apparatus are conveyed to the brain by the way of the vestibulocochlear nerve which is also called the eighth cranial nerve, or, less commonly, the auditory nerve.