Changes

Iguanids have a tympanic membrane which is nearly contiguous to the surface of the skin whereas it is deeper and recessed in scincids (such as the blue-tongue skink) and agamids (such as the bearded dragon). Lizards have very sensitive ears with delicate eardrums, and, like frogs and birds, a single auditory ossicle, the columella, that is coupled to the eardrum through a cartilaginous extracolumella.

Iguanids have a tympanic membrane which is nearly contiguous to the surface of the skin whereas it is deeper and recessed in scincids (such as the blue-tongue skink) and agamids (such as the bearded dragon). Lizards have very sensitive ears with delicate eardrums, and, like frogs and birds, a single auditory ossicle, the columella, that is coupled to the eardrum through a cartilaginous extracolumella.

'''Middle Ear'''

===Middle Ear===

Lizards have middle and inner ears; the tympanic membrane covers the middle ear cavity which is linked to the pharynx and eustachian tube. In general, the inner boundary of the middle ear cavity has two openings: a round one, covered by a thin membrane, and an oval opening that is uncovered.

Lizards have middle and inner ears; the tympanic membrane covers the middle ear cavity which is linked to the pharynx and eustachian tube. In general, the inner boundary of the middle ear cavity has two openings: a round one, covered by a thin membrane, and an oval opening that is uncovered.

The stapes (or stirrup) is a single bone that connects the eardrum to the inner ear; it crosses the middle ear cavity, from the inside of the tympanic membrane, its inner end fitted inside the oval opening. The outer end of the stapes has a cartilage cap which comes into contact with the tympanic membrane. In some reptiles, this cartilage, called the extrastapes, is attached to the quadrate (the primary support of the lower jaw). The upper and lower jaws of lizards contain several bones not found in mammals.

The stapes (or stirrup) is a single bone that connects the eardrum to the inner ear; it crosses the middle ear cavity, from the inside of the tympanic membrane, its inner end fitted inside the oval opening. The outer end of the stapes has a cartilage cap which comes into contact with the tympanic membrane. In some reptiles, this cartilage, called the extrastapes, is attached to the quadrate (the primary support of the lower jaw). The upper and lower jaws of lizards contain several bones not found in mammals.

'''Inner ear'''

===Inner ear===

The inner ear cavity comprises organs related to balance (the semicircular canals, utricle, and saccule) and hearing (cochlear duct). The cochlear duct and the saccule are both suspended in perilymphatic fluid; the cochlear is also filled with this fluid.

The inner ear cavity comprises organs related to balance (the semicircular canals, utricle, and saccule) and hearing (cochlear duct). The cochlear duct and the saccule are both suspended in perilymphatic fluid; the cochlear is also filled with this fluid.