Anatomy/ Physiology Outer Ear
Antihelix
- Above cymba concha - Separates the cymbal concha from a triangular depression - Continues around posterior to separate the concha from the remainder of the ear
EAC's Role in Amplification
- Acts as a resonator - Pinna: get increase of 3-4 dB from 3K-4K Hz - Concha: get increase of 10-15 dB From 1.5K to 7K Hz mostly around 5-6k Hz - EAC: get 10-15 dB at 2.5K Hz - Overall, getting 5 dB @ 1K, 15dB @ 2K, 20 dB @ 2.5-3K, 15 dB @5K Hz
End of EAC
- At end of EAC lies the tympanic membrane (TM) eardrum - TM is not usually considered part of the outer ear but then it isn't part of the middle ear either Boundary between the two
Localization
- Because of filtering properties, get a boost in the high frequencies, which helps to locate sounds, particularly from above and below - High-frequency amplification also helps in speech perception of consonants, particularly in background noise - Helps to color spectrum of sounds Theory that an individual gets use to the sound of his own pinna and EAC
Mastoid Process
- Behind ear - very thick - filled with holes/air
Cavum Concha
- Bowl-shaped depression at entrance to EAM
Central Auditory Nervous System includes
- Brain stem - Brain- cerebrum - corpus callosum
Antitragus
- Bump above lobe - Forms inferior outer ridge of concha
Outer Ear Physiology
- Cosmetic nature - Protection: - Protects TM - Cerumen helps collect foreign objects - Cerumen will move itself out of EAC on its own if it is pushed in too far (inner 2/3), there is no mechanism for natural removal
Triangular Fossa
- Depression above anti helix and below helix - Superior to opening to canal
External Auditory Canal (EAC)
- Extends medially and posterior for about 2.5cm in adults - Begins and ends with a slope downward allowing for drainage - Fungus may form at far end due to the downward slope - S-shaped - Lined with skin
Tragus
- Flap covering opening to ear canal - Greek for "goat's beard" - Some animals can close this
Tympanic Portion
- Forms bottom and sides of ear canal
Parts of Pinna
- Helix - Tragus - Cavum Concha - Crus of helix - Cymba concha - Antihelix - Antitragus - Lobe - Triangular Fossa
Squamous Portion
- Lies in Front and above ear canal - Fan-like portion
Petrous Portion
- Medial portion projecting inward - Contains organs of hearing and balance
Temporal Bone
- One of the bones of the skull - Contains the organs of hearing & balance
Peripheral auditory system includes
- Outer ear - Middle ear - Inner ear - VIIIth nerve (vestibulocochlear)
Outer 1/3 or EAC
- Passes through cartilage - Contains sweat glands called ceruminous glands - Contains sebaceous glands that produces sebum (fatty substance) - Together these form cerumen (wax) amber in color slight antibacterial and anti fungal characteristics - Contains hair follicles
Inner 2/3 of EAC
- Passes through tympanic section of temporal bone no glands no hair - osseocartilaginous junction point where the outer 1/3 and inner 2/3 of EAC meet Lies directly above the temporomandibular joint Site secondary pain for TMJ syndrome Get otalgia (ear pain) and edema (swelling)
Crus of Helix
- Ridge a top of caves concha - Divides concha into two areas
EAC Nerve Innervation
- Sensitive to tactile and pain stimulation Trigeminal (v), facial (VII), glossopharyngeal (IX) and Vagus (X) - Stimulate the inner canal portion coughing due to IX - Fainting combo of IX and X
Helix
- edge which runs around the edge
Outer Ear Anatomy
- most lateral and inferior portion of auditory pathway - part of the peripheral auditory system - Includes the pinna and the external auditory canal
Cymba concha
- upper portion of concha
Auricle or Pinna
Flap made of cartilage
Lobule
Most inferior part of pinna
External Auditory Meatus (EAM)
Opening into external auditory canal (EAC)
Four parts of the temporal bone
Squamous Portion Mastoid Process Tympanic Portion Petrous Portion
