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Skull: framework of the head; 22 irregular/
flattened bones joined by joints; liquid
protection is called CSF; tissues protecting the
brain is called meninges
2 Divisions of the skull: Cranium (8)-protects the
brain and Facial Skeleton (14) - mastification,
speech production, respiration, special senses
and facial expression
Temporal bone: most of the lateral base and
sides of the cranium; articulates with the
occipital, sphenoid, parietal and zygomatic
bones; joined to the mandible by a diarthrodial
(freely movable) joint located in the madibular
fossa
Parts: squamos (up)- temporal lobe;
mastoid (triangle, below) tympanic (below,
process)
Tympanosquamous suture; tympanomastoid
suture
Squamos- lateral, anterior and upper part of
temporal bones; suture with parietal bones;
outer surface: flat, smooth, convex and fanshaped; connected to zygomatic arch; provides
attachment to masseter muscle
Cranial nerve 5: trigeminal- biting; innervates
temporalis and masseter
Mastoid- attachment to sternocleidomastoid
and diagastric muscle (2 muscles to be
discussed in phonation); anteriorly fuses with
squamos; inferiorly fuses with tympanic,
triangular in shape; contain mastoid air cells
which are variable in size and shape;
communicates with tympanic cavity; MASTOID
PROCESS- antrum- large constant air cell;
tegmen- bony roof of tympanic cavity; aditus,
space before something
Tympanic part- thick curved plate of bone which
forms an incomplete ring; anterior-squamos
(tympanosquamos suture) posterior- mastoid
forms tympanomastoid suture; continuous with
the cartilaginous external auditory meatus;
forms floor of external auditory canal.
Styloid process (not a major part)- sharp pillar
of bone of variable length; serves as origin for 3
muscles: stylopharyngeus (swallowing),
styloglossus (articulation), stylohyoideus
(phonation); provides attachment to the
stylomandibular and stylohyoid ligaments
Petrous portion- located at the base of the
skull; houses essential part of organs of hearing
and equilibrium (cochlea); many foramina and
canals; hard bone: “Peter the Rock”
Internal auditory canal- Cranial nerve 7 and 8;
cerebellum- divides middle cranium fossa to
posterior cranium fossa; jugular vein-sigmoid
sylus, carotid artery.
Air Cell system functions:
-
Sound resonation
Insulation
Acoustic dissipation
Protection from trauma
Mucosal gas exchange (lessen
acidity or basisity)
Secretion control (Eustachian tube)
Acoustic enhancement
Pressure regulation (Eustachian
tube)
Lightening skull weight
Ear- outer auricle (Cartilage), external
auditory canal (cartilage and bony); middle
ear drum, ossicles (Eustachian tube, aditus ad
antrum), tympanic cavity; innercochlea,
semicircular canals: superior, lateral, anterior
(angular movement)
Atresia- no hole
Stenosis- smaller than usual hole
Energy transformation:
Acoustic energy (medium: air)mechanical
energy (bone medium) hydraulic (fluid
medium: perilymph and endolymph; electrical
(neural medium)
Pinna/ Auricle functions
- Sound collection- reflects and
directs sound into the eardrum;
each individual pinna creates a
distinctive imprint on the acoustic
wave traveling into the auditory
canal
- Sound localization
- Resonator
- Protection
Middle external ear- conductive (partial hearing
loss)
Inner ear- sensorineural (cranial nerve 8)
Pinna- resonates the souns
Outer ear- protection, resonance, transmission
Middle ear- impedance matching, energy
transformation mechanism, limited protection
Inner ear- transduction of mechanical and
hydrodynamic energy into neural impulses
Tympanic membrane- (air) external middle
(both) oval window: foot plate inner (fluid)
THE REAL HEARING ORGAN- auditory cortex
E igth nerve
C ochlear nucleus
O livery nucleus (superior)
L ateral lemniscus
I nferior colliculus
M edial geniculate body
A uditory cortex
Heschl’s gyrus- superior temporal gyrus;
hearing; brodman area #41 and 42
Wernicke’s area- understand
Broca’s area- speaking
Outer Ear 1. Pinna/ auricle (darwin’s tubercle:
normal variant)- embryology 1st and 2nd
branchial arches 2. External auditory canal 3.
Tympanic membrane
Microtia- small maldeveloped pinna
Anotia- no pinna
Pinna innervation- cranial nerve 5 , 10 and
cervical nerves
1.
2.
3.
4.
Great auricular nerve
Lesser occipital nerve
Auricular branch of vagus
Auriculotemporal nerve
1,2 – cervical erve 3,4- cranial
nerve
Cranial nerve 12- hypoglossaltongue movement
Autoeithic organs- linear movement
Semicircular canal- angular movement
TYMPANIC MEMBRANE: pars flassida- superior
loose; pars tensa- tensed (vibration)
Annulus fibrous 1/3 cartilaginous 2/3 bony