Three Parts of Ear 1. Inner ear - hearing and equilibrium 2. Middle ear - hearing 3. Outer ear - hearing
Outer Ear
Auricle and External acoustic meatus
Auricle: • Composed of elastic cartilage covered in thin skin
• Helix (rim)
• Lobule (earlobe) (no cartilage)
• Directs sound wave into external acoustic meatus External auditory canal:
• Short, curved tube - 2.5cm long
• Extends from auricle to ear drum
• Near auricle framework is elastic cartilage
• Remainder inside temp bone
• Lines skin with ceruminous glands (secrete ear wax, sticky trap for foreign bodies) Tymphanic Membrane (Eardrum)
• Thin CT membrane, vibrates in response to sound
• Transfers sound energy to middle ear ossicles
• Boundary between outer and middle ears
• Connects with pharynx Middle Ear (Tympanic Cavity) Small, air filled, mucosa lined cavity. Petrous portion of temporal bone (laterally by eardrum, flanked medially by bony wall that containts oval (superior) + round (inferior) windows.Epitympanic recess: • Roofofmiddleear Pharyngotympanic Tube
• Connects middle ear to nasopharynx
• Equalises pressure in the middle ear cavity with external air pressure
• Eardrum vibrates freely only if pressure on both sides is equal Ear Ossicles Tympanic cavity contains three of the smallest bones in the body 1. Malleus (hammer) - secured to eardrum 2. Incus