It is essential for sound transmission in the inner ear, as perilymph is a fluid, and fluids are essentially non-compressible. The round window is a circular window that moves out upon sound transmission. The scala tympani lies below the scala media, and is separated from the scala media by the basilar membrane. The organ of Corti lies within the scala media. The scala media lies between the scala vestibuli and the scala tympani and contains endolymph. Here the sound wave vibrations continue and head back down the cochlea via the scala tympani. It receives the sound waves from the oval window, and sends them up to the apex of the cochlea (the helicotrema). It is separated from the scala media by Reissner’s membrane. The scala vestibuli is the semicircle shaped region above the scala media and contains perilymph. The oval window is quite simply an oval shaped window that is moved inwards by the movement of the stapes footplate. The cochlear duct is the triangular shaped section of the cochlea, which contains the organ of Corti. The cochlea(the region responsible for hearing) is a spiral shaped hollow organ. This region is found within the bony labyrinth. It passes through the middle ear on its way to the tongue. This nerve provides taste to the anterior two thirds of the tongue, and is a branch of the facial nerve (cranial nerve 7). It arises from the cone shaped eminence in the posterior part of the tympanic cavity known as pyramidal eminence, and inserts onto the neck of the stapes. Bell’s palsy), one of the symptoms is pain on hearing noises (especially loud noises) on the affected side, due to a lack of innervation of the stapedius. Hence in facial nerve palsy (usually a lower motor neurone i.e. It stabilizes the stapes, and is innervated by the facial nerve ( cranial nerve 7). The stapedius is the smallest skeletal muscle in the human body, and is just over a millimeter in length. Its footplate articulates with the oval window via the annular ligament. It develops from the second pharyngeal arch, and is the last ossicle of the middle ear. This is the smallest bone in the human body. However its involuntary function is most important. It arises from the greater wing of sphenoid and auditory canal and can be voluntarily controlled. The tensor tympani muscle attaches onto the neck of the malleus, and its role is to dampen sounds. There are anterior, lateral and superior malleal ligaments, which maintain the position of the malleus at the level of the head, neck and head of the malleus respectively, dampen the response of the ossicles to excessively loud sounds, and also reduce the displacement of the ossicles when middle ear pressure changes. The anterior process is attached to the petrotympanic fissure. The lower part of the malleus is attached to the tympanic membrane at the umbo, and is a strong connection. The lateral process of the malleus is attached to the upper part of the tympanic membrane. This small bone is connected with the tympanic membrane via its manubrium and with the incus via its articulating facet. The malleus, or hammer in Latin, develops from the first pharyngeal arch cartilage, like the mandible and maxilla jawbones. Finally the auricular sulcus is the depression that lies posterior to the ear. The concha is the hollow region that lies adjacent to the external ear opening.
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The lobe is either attached or free (genetic determination). The space between the tragus and antitragus is called the incisura anterior auris. The tragus and antitragus are the cartilaginous prominences that lie anterior and inferior respectively to the external auditory opening. The groove between the helix and anti-helix is called the scapha. It has an inferior and superior crus that lie either side of the fossa triangularis.
The antihelix is a y-shaped region of ear cartilage. The helix is the folded outer edge of the ear. The external auditory canal is the opening of the ear. The pinna has a number of features on its surface, which we will now discuss. By funneling the sound waves in this way, it is able to direct them into the auditory canal and amplify them. It collects omnidirectional sound waves and transforms them into a unidirectional source of information. The outer ear/visible ear is referred to as the pinna.
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