ACTIVITY 5A STUDENT HANDOUT Glossary: Description and Function of Parts of the Human Ear the Three Functions of the Middle

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ACTIVITY 5A STUDENT HANDOUT Glossary: Description and Function of Parts of the Human Ear EXTERNAL EAR AURICLE: the ear flap, ear lobe, or outer ear (pinna); collects sound waves and transmits them through the external acoustic meatus (auditory canal) to the tympanic membrane. EXTERNAL AUDITORY CANAL : an S-shaped structure about 2 cm in length, lined with numerous glands secreting a yellow, waxy substance, cerumen. CERUMEN: yellow, waxy substance; lubricates and protects the ear; “ear wax.” MIDDLE EAR TYMPANIC CAVITY middle: ear, tiny cavity in the temporal bone; holds the three auditory ossicles; has five openings (opening covered by the tympanic membrane), the opening of the auditory tube (eustachian tube) which connects the middle ear with the nasopharynx and through which outside air can enter; the opening into the mastoid cavity, the openings in to the inner ear (round and oval windows). TYMPANIC MEMBRANE: eardrum. AUDITORY OSSICLES: three tiny bones of middle ear, including malleus (hammer), incus (anvil), and stapes (stirrup). STAPEDIUS MUSCLE: attached to the stapes. TENSOR TYMPANI MUSCLE: attached to the handle of the malleus. EUSTACHIAN TUBE: connects middle ear with mouth to equalize pressure. The three functions of the Middle Ear 1. TRANSMIT ENERGY from sound vibrations in the air column of the external auditory meatus across the middle ear into the fluid contained within the cochlea (central hearing apparatus); bones of middle ear pick up the vibrations from the tympanicmembrane and transmit them across the middle ear to the oval window (the opening to the inner ear). 2. PROTECTIVE: reduces the amplitude of vibrations accompanying intense sounds of low frequency; contraction of the tensor tympani and the stapedius restricts the motion of the chain of ossicles and minimizes shock to the inner ear. 3. EQUALIZE AIR PRESSURE on both sides of the membrane via the auditory tube to prevent the tympanum from rupturing. INNER EAR Consists of bony and membranous labyrinths, composed of a series of canals hollowed out of the temporal bone, filled with perilymph; membranous labyrinth, lying entirely within the bony labyrinth, is filled with endolymph. BONY LABYRINTH: consists of the cochlea, containing the organ of hearing (organ of Corti), and the vestibule and semicircular canals containing the organs of equilibrium. MEMBRANOUS LABYRINTH: consists of the cochlear duct within the cochlea, the 6 utricle and saccule within the vestibule, and the semicircular ducts within the semicircular canals; those portions of the inner ear concerned with equilibrium are

collectively called the vestibular apparatus. UNIT