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The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear.The adult human ear canal extends from the auricle to the eardrum and is about 2.5 centimetres (1 in) in length and 0.7 centimetres (0.3 in) in diameter.
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates , the inner ear is mainly responsible for sound detection and balance. [ 1 ] In mammals , it consists of the bony labyrinth , a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts: [ 2 ]
The stapedius reflex of the middle ear muscles helps protect the inner ear from damage by reducing the transmission of sound energy when the stapedius muscle is activated in response to sound. The middle ear still contains the sound information in wave form; it is converted to nerve impulses in the cochlea .
The inner ear comprises three specialized regions of the membranous labyrinth: the vestibular sacs – the utricle and saccule, and the semicircular canals, which are the vestibular organs, as well as the cochlear duct, which is involved in the special sense of hearing.
The outer ear is the external portion of the ear and includes the fleshy visible auricle, the ear canal, and the outer layer of the eardrum (also called the tympanic membrane). [2] [3] The auricle consists of the curving outer rim called the helix, the inner curved rim called the antihelix, and opens into the ear canal.
The tympanic nerve (Jacobson's nerve) is a branch of the glossopharyngeal nerve passing through the petrous part of the temporal bone to reach the middle ear. It provides sensory innervation for the middle ear, the Eustachian tube, the parotid gland, and mastoid cells. It also carries parasympathetic fibers destined for the parotid gland.
To nuclei of cranial nerves III, IV, and VI. Signals sent to these nerves cause the vestibular-ocular reflex. They allow the eyes to fix on a moving object while staying in focus. To the reticular formation. Signals sent to the reticular formation signal the new posture the body has taken on, and how to adjust circulation and breathing due to ...
The auriculotemporal nerve is a sensory branch of the mandibular nerve (CN V 3) that runs with the superficial temporal artery and vein, and provides sensory innervation to parts of the external ear, scalp, and temporomandibular joint. The nerve also conveys post-ganglionic parasympathetic fibres from the otic ganglion to the parotid gland. [1]