EARS

• What 3 regions is the ear divided into

  1. External (outer) ear

  2. Middle ear

  3. Internal (inner) ear
• What is the function of the external ear

  To collect sound waves and direct them inwards
• What does the external ear consist of

  1. The pinna/auricle

  2. The external auditory canal/meatus (EAM)
• What is the pinna/auricle

  A flap of elastic cartilage covered in thick skin
• What is the external auditory meatus (EAM)

  2.5cm curved tube in the temporal bone which leads to the tympanic membrane
• What prevents objects from entering the ear

  Hairs and sebaceous glands which secrete cerumen (ear wax) near the exterior opening
• What is the tympanic membrane (eardrum)

  1. Thin, semi-transparent partition between the EAM and middle ear

  
  

  2. Concave external surface covered with skin

  
  

  3. Convex internal surface covered with mucous membrane
• What is the middle ear

  An air filled cavity within the petrous portion of the temporal bone
• What separates the middle ear from the external ear

  The tympanic membrane (eardrum)
• What separates the middle ear from the internal ear

  A thin bony partition that contains two openings - the oval window & the round window
• What does the anterior wall of the middle ear contain

  An opening which leads directly to the auditory/Eustachian tube
• What does the Eustachian tube do

  1. Connects middle ear with the nasopharynx

  
  

  2. Equalises air pressure on both sides of the tympanic membrane to prevent rupture of the membrane

  
  

  3. Acts as a route for pathogens to travel from the nose and throat to the middle ear
• What is an infection of the middle ear called

  Otitis media
• Where do the auditory ossicles lie

  Within the middle ear
• What are the auditory ossicles (3 smallest bones in the body)

  1. The malleus (hammer)

  
  

  2. The incus (anvil)

  
  

  3. The stapes (stirrup)
• How are ossicles connected

  By synovial joints
• How are ossicles attached to the cavity

  By ligaments/muscles
• What do ossicles do

  Reduce the amplitude and range of oscillations within the ear to protect the ear structures from damage due to loud noise
• What is the handle of the malleus attached to

  The internal surface of the tympanic membrane
• What does the head of the malleus articulate with

  The body of the incus
• What does the incus articulate with

  The head of the stapes
• What does the base of the stapes fit into

  The oval window which sits between the middle and inner ear
• What is found beneath the oval window

  The round window
• What is the inner ear also known as

  The labyrinth
• What is the inner ear

  A complex series of canals that form the bony and membranous labyrinth
• Where is the inner ear located

  In the petrous portion of the temporal bone
• What is the bony labyrinth

  A series of cavities in the temporal bone
• What is the bony labyrinth divided into

  1. Vestibule

  
  

  2. Cochlea

  
  

  3. Semi-circular canals
• What is the bony labyrinth filled with

  A fluid called perilymph
• What does the perilymph of the bony labyrinth surround

  The membranous labyrinth
• What is the membranous labyrinth

  A series of sacs and tubes lying inside and following the same from as the bony labyrinth
• What does the membranous labyrinth contain

  Endolymph
• What are the semi-circular canals

  1. 3 bony canals that project upward and posteriorly from the vestibule

  
  

  2. Lie at approximate right angles to each other

  
  

  3. Named based on their positions
• What are the names of the 3 semi-circular canals

  1. Anterior semi-circular canal

  2. Posterior semi-circular canal

  3. Lateral semi-circular canal
• What does the end of each semi-circular canal do

  Enlarges into a swelling called the ampulla
• What are the semi-circular ducts

  The membranous labyrinths within the semi-circular canals
• What lies anterior to the vestibule

  The cochlea
• What is the cochlea

  1. A shell like appearance

  
  

  2. 2 3/4 turns

  
  

  3. Contains hair cells that act as receptors for auditory sensation - free ends of the hair cells extend into the endolymph of the membranous labyrinth

  
  

  4. Basal ends of these cells are in contact with the fibres of the cochlear branch of the vestibulocochlear nerve
• What do sound waves result from

  The alternate compression and decompression of air molecules
• What do sound waves originate from

  A vibrating object