Parts of the auditory system Peripheral External ear Middle ear Inner ear Auditory nerve Central Cochlear nucleus Superior olivary complex Lateral leminiscus Inferior colliculus Medial geniculate body Auditory subcortex Cortex Interhemispheric pathways

Anatomical terms Planes of section: Frontal/Coronal: Front and back Sagittal: Left and right Median/Midsagittal: Through the center Axial/Horizontal/Transverse: Upper and lower http://www.spineuniverse.com/displayarticle.php/article1023.html

Anatomical directions Anterior/Ventral: Front Posterior/Dorsal: Back Inferior: Bottom Superior: Top Lateral: Away from median plane Medial: Toward the median plane

Anatomy of the auditory system Contained in the temporal bone Located on the sides of the skull

Parts of the temporal bone Squamous Mastoid Tympanic Petrous Medial view of right ear. Note: IAM is internal auditory meatus, which is different from the external auditory meatus. Lateral view of right ear

Anatomy of the ear http://www.iurc.montp.inserm.fr/cric51/audition/english/ear/fear.htm http://www.wiley.com/legacy/college/bio/tortora366927/resources/student/anatomydrill/ch16.html

Parts of the auditory system Peripheral External ear Middle ear Inner ear Auditory nerve Central Cochlear nucleus Superior olivary complex Lateral leminiscus Inferior colliculus Medial geniculate body Auditory subcortex Cortex Interhemispheric pathways

External ear Consists of Auricle or Pinna: Mostly cartilage External auditory canal/meatus http://www.ghorayeb.com/AnatomyAuricle.html

Parts of the Pinna Concha: Bowl or deep central portion Helix: Prominent ridge that begins superior to the opening of the canal and runs around the pinna Antihelix: Interior ridge parallel to the helix Triangular fossa: Triangular depression formed anteriorly and superiorly by the helix Lobule: Most inferior part of the pinna Tragus: Small flap at the anterior side of the concha

External auditory meatus Length is approximately 28 mm Diameter is approximately 7 mm Not perfectly straight Ends in the tympanic membrane Outer half of the canal formed by cartilage Skin secretes cerumen Medial part formed by bone from the squamous and tympanic portions of the temporal bone

External ear functions Modifies the spectrum of incoming sounds. Resonance of external auditory meatus Head related transfer functions Protection to middle and inner ear structures

Resonance of ear canal Resonance of ear canal: Around 2.5 kHz Resonance of the concha: Around 5 kHz Net effect: Boost in frequency region between 1.7 and 7 kHz

External ear functions Modifies the spectrum of incoming sounds. Resonance of external auditory meatus Head related transfer functions Protection to middle and inner ear structures

Head-related transfer functions Inter-aural amplitude/level difference Inter-aural time difference Important for sound localization