Describe the structure and function of the parts of the human ear. Describe the structures of the inner ear that create the sensations of balance and of hearing.
The human ear has three main parts: the outer ear, the middle ear, and the inner ear. The auditory canal of the outer ear connects the pinna or ear flap to the tympanic membrane or ear drum. From the tympanic membrane, three tiny bones, the malleus or hammer, the incus or anvil, and the stapes or stirrup, extend across the middle ear to the membrane covering the oval window. The membrane-covered round window is located just below the oval window and just above the Eustachian tube which connects to the pharynx and helps to equalize the air pressure between the outer and middle ears. The oval and round windows sit in the cochlear wall of the fluid-filled inner ear. The inner ear has upper and lower potions. The upper portion of the inner ear has three loops called the semicircular canals and two chambers called the utriculus and the sacculus. The upper portion of the inner ear helps organisms maintain their sense of equilibrium or balance. Changes in the position of the head cause calcium carbonate crystals to shift on their bed of sensory hairs in the utriculus and the sacculus. The changes as to which hairs are being stimulated by the presence of crystals are reported to the cerebellum which, then, translates the information into knowledge of the position of the head relative to gravity. The lower portion of the inner ear, called
