Temporal:
It
is an important bone because
·
Whole internal ear
·
Whole middle ear
·
Bony part of external auditory meatus lies within
it .
SN:
Only cartilaginous part of external auditory meatus and auricle lies outside
the temporal bone
1.
Anatomical point :
·
Convex squamous part is directed laterally
·
Apex of petrous part is directed medially ,
forward, and upward
·
Zygomatic process is directed anteriorly
2.
Morphological
type : pneumatic irregular bone
3.
Ossification
: both intramembranous and intracartilaginous
· Squmous
part and tympanic part is ossify from membrane
· Rest of
the temporal bone is ossify from cartilage
4.
Development
:
Petrous part of temporal bone is derived from paraxial
mesoderm
Rest of the part of temporal bone is derived from neural crest
5. Parts: It has
Three parts:
i.
Squamous part
ii.
Petro-mastoid part
iii.
Tympanic part
Three processes:
It has three processes :
i.
Zygomatic process
ii.
Mastoid process
iii.
Styloid process
Squamous
part : it has two surfaces
External surface:
i)
whole external
surface is attached by origin of temporalis muscle except mandibular
fossa and zygomatic process
ii)
external surface bears groove for middle temporal
artery
iii)
Suprameatal triangle : a triangle just below
the external auditory meatus
iv)
Importance of suprameatal triangle : mastoid
antrum lies 1.25 cm deep to it
Internal surface:
Impressions
of temporal lobe of cerebrum
Groove
for middle meningeal artery
Squamous
part has two borders
· Superior
border articulate with inferior border of parietal bone
· Antero-inferior
border : articulate with greater wing of sphenoid bone
Petrous part: It has
Apex:
is
directed medially, forward and upwards
Base:
attached
with squamous and mastoid part
Petrous part : 3 borders:
1. Anterior border:
articulate with greater wing of sphenoid
2. Superior border: lodges superior petrosal sinus and attachment
of tentorium cerebella except medial part
3. Posterior border:
Medial
part of posterior border is lodge by inferior
petrosal sinus and
Lateral
part of posterior border forms jugular
foramen by articulating with condylar part of occipital bone
3 surfaces of petrous part :
anterior, posterior and inferior
Anterior surface of petrous part :
1.
This
surface is
irregular for sulci and gyri of temporal lobe of cerebrum
2. Trigeminal impression ( a
depressed area near the apex ): lodge
trigeminal ganglion
3. Arcuate eminence: an
elevated area behind the trigeminal impression, it is caused by superior
semicircular canal of internal ear
4.
Tegmen
tympani: a thin
plate of bone situated in between arcuate eminence and squamous part of
temporal bone.
From
antero- posteriorly , tegment tympani forms
1. Roof of
tensor tympani
2. Roof of middle
ear cavity
3. Roof of
mastoid antrum
Posterior surface of petrous part of temporal
bone:
Bear
orifice of internal auditory meatus : Structure passing through the foramen
Structures
entrance into internal auditory meatus :
·
Motor root of facial nerve
·
Labyrinthine artery
Structures
exit from the internal auditory meatus:
·
sensory root of facial nerve
·
vestibulocochlear nerve
·
labyrinthine vein
Inferior
surface of petrous part of temporal bone:
From antero posteriorly
1. Near apex:
attachment of levator veli palatine muscle and cartilaginous part of auditory
tube
2. External
or lower opening of carotid canal
3. Jugular
fossa
Mastoid part
It
forms the posterior part of temporal bone. It has
Two
surfaces: external and internal
Two
borders: superior and posterior
1
process: mastoid process
External surface of mastoid part
It
is attached with following muscles: muscles are arrange from above, downwards
and forwards
i.
Auricularis posterior
ii.
Origin of occipital belly of occipito frontalis
muscle
iii.
Insertion of sternocleidomastoid
iv.
Insertion of splenius capitis
v.
Insertion of longissimus capitis
Internal
surface of mastoid part
Sigmoid
sulcus : a deep groove which lodge sigmoid sinus
Two borders of mastoid part :
·
superior border articulate with inferior border of
parietal bone
·
posterior border articulate with inferior border
of squamous part of occipital bone
Tympanic
part
·
A thin plate of bone lies between the squamous and
mastoid parts
·
Anterior surface form non articular part of
mandibular fossa
·
Posterior surface forms greater part of external
auditory meatus
Processes
of temporal bone
i.
Zygomatic
process :
· medial
surface and lower border of zygomatic process give origin of masseter muscle
· Superior
border of zygomatic process attached with temporal fascia
· Anterior
end of zygomatic process articulate with temporal process of zygomatic bone
ii.
Mastoid
process :
External
surface of mastoid process is attached with
a)
Insertion of sternocleidomastoid
b)
Insertion of splenius capitis
c)
Insertion of longissimus capitis
Mastoid notch:
a
deep notch at the medial surface of mastoid process gives origin of posterior
belly of digastric muscle
Mastoid
foramen near the posterior border of mastoid part of temporal bone :
it transmit an emissary vein which connect sigmoid sinus with posterior
auricular vein
iii.
Styloid
process
Muscles:
· origin of
styloglossus, stylohyoid and
stylopharyngeus
Ligaments:
· stylohyoid
and stylomandibular ligament
Stylomastoid
foramen:
· It is
situated in between mastoid process and styloid process
It
transmitted
· Facial
nerve exit
· Entrance
stylomastoid branch of posterior auricular artery
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