The skull Flashcards
Tell me about the frontal bone…
Neurocranium - anterior to parietal bones, superior to sphenoid, ethmoid, zygomatic, lacrimal, nasal bones and maxillae
Flat bone
Key features: - squamous, orbital and nasal part, supraorbital margin, superciliary arch, fossae for lacrimal glands and zygomatic processes
Meets with: parietal bones, nasal bone, sphenoid bone, lacrimal bone, ethmoid bone, zygomatic and maxillae
Arterial supply: Middle menigneal artery
Parts: squamous, orbital and nasal parts
Surfaces: external, internal, orbital, cerebral surfaces, parietal, sphenoidal, nasal and supreorbital margins
Landmarks - superciliary arches, fossae for lacrimal glands, zygomaitic processes, groove for superior sagittal sinus, frontal eminences (bumps on top of your forehead) and temporal lines
Meets - pareital bone at coronal suture
- ethmoid bone at frontoethmoidal suture
- lacrimal bones at frontolacrimal suture
- maxillae at frontomaxillae suture
- nasal bones at frontonasal suture
- zygomatic bones at frontozygomatic sutures
- sphenoid bone at sphenofrontal sutures
ossification
- 4 centres
- right and left eminences with one centre found in each, which appear in utero in the 2nd month
- at the nasal spine, which appear during the second year
the right and left halves of the frontal bones remain unfused with the metopic suture located between them, they fuse together within the first year of birth
Variations
- frontal sinus may be absent unilaterally or bilaterally,
- metopic suture may be present in adults
- frontal bones and temporal bones meet each other and articulate, resulting in the parietal and sphenoid bones not meeting each other and therefore not articulating
Sexual dimorphism, superciliary arched tend to be more prominent in males
clinical correlates
- hypercortosis frontalis interna - thickening of inner side of frontal bone of the skull, often in women in menopause and assymptomatic
- craniosynostosis - bones in the baby’s skull join together too early, happens before the baby’s brain is fully grown
Zygomatic bone
Viscerocranium - articulates, frontal bone, sphenoid bone, temporal bone and maxilla
irregular bone
-inferior to the frontal bone, anterior to the sphenoid and temporal bone, superior to the mandible, lateral to the maxilla
Key features: Temporal, frontal and maxillary processes, lateral, temporal and orbital surfaces and orbital tubercle
arterial supply - Zygomaticoorbital artery
- Quadrilateral bones found along the anterolateral aspect of the cranium
- contribute to the formation of the orbits and the viscerocranium
parts - temporal, frontal, maxillary processes
surfaces- lateral, temporal, orbital surfaces, maxillary, sphenoid, temporal, masseteric and orbital borders
Landmarks - orbital tubercle, and the zygomatic portions or infraorbital margin, zygomatic arch and temporal fossa
Articulation with sutures
- frontal bone at frontozygomatic suture
- sphenoid bone at sphenozygomatic suture
- temporal bone at a temporozygomatic suture
- maxilla at the zygomaticomaxillary suture
Ossification of each zygomatic bone occurs at one ossification centre which appears in utero during the second months
Variations -
- zygomatic bone may be present in the bipartite condition (divided into 2 parts) known as a japonicum
- accessorary zygomaticofacial foramina may be present
- the orbital tubecle may be absent
surface anatomy - lateral surface and orbital, temporal and masseteric borders are all subcutaneous and can be easily palpated.
- the zygomatic arch which is formed by both the zygomatic process of temporal bones and temporal process of zygomatic bone is palpable
clinical correlates
- fracture of zygomatic bone
- osteomyelitis - infection of the bone
- zygomatic arch dysplasia
Vomer
Viscerocranium
Flat bone
cuneiform part and alae, lateral surfaces, vomerine groove, vomerine crest of choana and nasopalatine groove.
meets with sphenoid bone, ethmoid bone, palatine bone and maxillae
sphenopalatine artery
single, thin, quadritelateral bond. Flat bone and forms the bony nasal septum, nasal cavities and viscerocranium.
parts- cuneriform part and alae.
surfaces - lateral anterior posterior, superior and inferior borders
landmarks - vomerine groove, vomerine crest of choana and nasopalative groove
Location - inferior to sphenoid bone at the sphenovomerine suture
ethmoid bone
maxillae
palative bone
ossification - 2 centres, one on right and one on left half. these appear in utero in the 2nd month. fuse with each other in 3rd month and finish in puberty
note the shape of the vomer can change and may be absent.
clinical correlates - fracture of the vomer and the nasal septum deviation.
Mandible
Viscerocranium
Bone type- Irregular bone.
Key features - Body, rami, angles, myolohyoid lines, mental protudence, mandibular symphysis, alveolar condylar, coronoid process.
Articulates with temporal bones.
Inferior alveolar artery and sublingual artery, submental artery
Parts - Body, rami, alveolar, cordylar ad coronoid processes
Surfaces - internal, external surfaces of the body, medial and lateral surfaces of the rami and anterior and posterior borders of the rami, base of the mandible
Landmarks- mandibular symphysis, mylohyoid and oblique lines, sublingual and submandibular fossae and superior and inferior mental spines.
superior to Hyiod bone
inferior to the temporal, zygomatic and maxillae
Ossification - R + L halves of the mandible which occur in the utero during the second month
- R+L cordylar processes and coronoid processes appear in utero later
- The mental protudence occur in the seventh month
each half fuses with the cordylar and corornoid process on same side before birth.At birth the right and left halves of the mandible remain unfused with mandibular symphasis in between them, they fuse within the first 2-3 years of birth. The mental protudences fuse in the first year of birth.
Variations - with age and size, shape
accessory mental foramina may be present
coronoid processes may be enlogated.
a bony outgrowth may be present along the internal surface of the body of the mandible - TORUS MANDIBULARIS. inside the mouth
+ shows sexual dimorphism - where they are bigger in males
surface anatomy - the rami, alveolar process, coronoid and cordylar processes, oblique lin, angle of the mandible, the mental protudences can be palpated
CLINICAL CORRELATES
- Fractures
- dilocation
- temporomandibular joint dysfunction
- micromanathism
- macromagnathism
- hyperplasia or coronoid or condylar process
Nasal bone
Viscerocranium
flat bone
Crest, ethmoid groove, internal and external surfaces, superior, inferior, medial and lateral borders
Meets with opposite nasal bone, ethmoid bone and the maxillae and frontal bone
Opthalmic and angular artery
Small pair of quadrilateral bones. contribute to the formation of the bridge of the nose, roof of nasal cavity and viscerocranium.
opposite nasal bone with the internasal suture,
frontal bone with the frontonasal suture
maxila nasomaxillary suture
ethmoid bone
one ossification centre -
appears in utero at third month
Variation
- for some they are asymmetrical
And may have more than 2 or appear as single
external surface of the nasal bone can be palpated as it is subcutaneous
-Fracture and dislocation of the bone
sphenoid bone
Neurocranium
irregular
Body, the lesser and greater wings. Medial, lateral plates of the pterygoid process, sella turcica (pituitary gland located) and anterior and posterior clinoid processes
Meets with frontal bone, temporal bone, parietal bone, ethmoid bone, zygomatic bone, occipital bone, palatine and vomer.
middle meningeal artery
internal carotid artery
Has the 2 R+L sphenoidal sinuses.
Parts - greater and lesser wings and the pterygoid processes
Sufaces - anterior posterior, and inferior of the body. cerebral, temporal, infatemporal maxillary and orbital surfaces of the greater wings and superior and inferior surfaces of the lesser wings.
Landmarks - anterior and posterior clinoid processes, chiasmatic sulcus, tuberculum sellae and dorsum sellae and carotid sulci
Meets with - frontal at the sphenofrontal suture
- parietal - sphenoparietal sutures
- temporal - sphenosquamous sutures and spheno petrosal synchondorses.
- occupital bone - sphenooccipital synchondrosis
- zygomatic bone at sphenozygomatic sutures
- ethmoid bone - sphenoethmoidal sutures
palative bone
vomer at sphenovomerine suture
ossification centre - at the body which occurs at the 3rd and 5rd month in the utero
- greater and lesser wings in the utero in the 3rd month
lesser wings fuse in the utero and the greater wings in the first year of life
Variations -
- sella turcica may be absent
- sphenonoidal sinuses my be present in different sizes and shapes
- sphenoidal foramen - foramen of vesalius may be present in the greater wing of the sphenoid bone
- the frontal bones and temporal bones may meet each other cause sphenoid and parietal not to meet
- fracture
- osteomyelitis of sphenoid bone
- craniosynostisis
Maxillae
viscerocranium
Irregular bone
zygomatic, frontal, palatine and alveolar processes body, canine fossa, maxillary tuberosity and anterior lacrimal crest.
meets with maxilla, ethmoid bone, zygomatic, nasal, palatine and lacrimal, vomer and inferior nasal concha
Facial artery and maxillary artery.
upper teeth and formation of orbits and nasal cavities and bony hard palate. And maxillary sinuses
Parts - zygomatic, frontal, alveolar, palatine processes and body.
surfaces - anterior, infratemporal, orbital, nasal and palatine surfaces, orbital, ethmoidal, zygomatic, lacrimal and nasal margins
- canine fossa, canine eminence, maxillary tuberosity anterior lacrimal crest, conchal and nasal crests.
Meets with opposite maxilla at intermaxillary and median palatine sutures
lacrimal bone at lacrimomaxillary suture
palatine bone at palatomaxilary and transverse palatine suture
frontal bone at the frontomaxilary suture
ethmoid bone at the ethmoidomaxilary suture
zygomatic bone at the zygomaticomaxillary suture
nasal bone at the nasomaxillary suture
vomer
inferior nasal concha
Ossification occurs at the centre - at thet body at the 2nd month and also at the zygomatic, frontal, alveolar and palatine processes
Variations -
- accessory infraorbital foramina
- maxillary sinus may be underdeveloped and contain septum
- incisive portion of the alveolar process may not be fused with the rest of the maxilla and result as os incivisum
displays sexual dimorphism - larger in men than women
Body, alveolar and palatine processes can be palpated
Fracture of maxilla ( Le Fort fractures)
cleft palate
maxillary hypoplasia - less growth at the maxilae so underbite
occipital
neurocranium
flat bone
squamous, basilar, lateral parts. cerebellar and cerebral fossae. superior and inferior nuchal lines, internal and external occipital protudences
meets with parietal bones, temporal and sphenoid but also atlas.
middle meningeal artery
posteinferior aspect of the cranium
Parts - the basilar, squamous and lateral parts
surfaces - cerebral and cerebellar fossae and the superior and lateral angles and the mastoid and lamboid borders
nuchal lines, occipital protuberances, occipital condyles and occipital crest
parietal bones at thte lamboid suture
temporal bone at the occipitomastoid suture and the petrooccipital synchondroses
sphenoid bone at the sphenooccipital synchondrosis
atlas at the atlantoccipital joints
ossification centres -
9 centres, at the squamous part about 4 formed there at the 2nd month
basilar part - one centre formed in the 2nd month
right and left lateral parts 2 centres in each and appear at the 2nd month in utero
at birth all unfused but the squamous and the lateral fuse with each other during the 2nd year and the lateral and basilar parts fuse during 3-4 years
Variations -
3rd occipital condyle present
fused at atlas - atlantooccipital assimilation
superior portion of squamous part of the bone may fail to fuse with rest of the bone resulting in the presence of interparental bone known as Inca bone
external occipital protudence and nuchal lines superior ones can be palpated
- fracture of bone
- occipital horn syndrome
craniosynostosis
Atlas
C1
absence of vertebral body and spinous process.
irregular bone
- parts - lateral masses, anterior and posterior arches and transverse processes
- Landmarks - superior, inferior articular articular facets, anterior and posterior tubercles, grooves for vertebral arteries and transverse ligament tubercles
meets with the axis at the median and lateral atlantoaxial joints
and occipital bone at the atlantooccipital joints
ossification -
3 centres
R+L lateral masses appearing at the 2nd month
anterior arch appear during 1st year after birth
the right and left masses fuse together to form posterior arch during 3-4 years. anterior arch fuse in 6-8 years with lateral arches
Variation
- posterior arch may be incompletely fused
- superior articular facets may be present in bipartite condition (divided into 2 parts)
- may be fused with occipital bone known as atlantooccipital assimilation
posterior tubercle is hard to palpate as it lies deep into the nuchal ligament
- fracture
- osteoporosis
- spinal stenosis
- scoliosis
- atlantooccipital assimilation
- dislocation of atlantooccipital joints and atlantoaxial joints
- spina bifida
Lacrimal bone
viscerocranium
irregular bone
medial, lateral surfaces, descending process, posterior lacrimal crest, lacrimal groove and lacrimal hamulus
meets with ethmoid bone, frontal bone, inferior nasal concha and maxilla
facial artery and maxillary artery
small thin bones which are found along medial walls of each orbital cavity
medial and lateral surfaces, anterior, posterior and superior inferior borders
posterior lacrimal crest and lacrimal groove and lacrimal hamulus
ethmoid bone at lacrimoethmoial suture
maxilla at lacrimomaxillary suture
inferior nasal concha at lacrimoconchal suture
frontal bone at the frontolacrimal suture
ossification - at the centre which occurs at the utero at the 3rd month
Variation
the shape can vary
there may be an extra ossicle present an accessory one
fracture
Parietal bone
neurocranium
flat bone
frontal occipital, sphenoidal, mastoid angles, internal and external surfaces, parietal eminence and superior and inferior temporal lines
middle meningeal artery
large, quadrilateral found along the superolateral aspects of the cranium
Part: frontal, occipital, sphenoidal and mastoid angles
Surfaces: internal and external surfaces and sagittal, occipital, frontal and squamosal borders
landmarks: superior and inferior temporal lines, parietal eminence, grooves for the sigmoid and superior sagittal sinuses
opposite parietal lobes - at the sagittal suture
frontal - coronal suture
occipital at the lambdoid suture
temporal at the squamous and parietalmastoid sutures
sphenoid bone at the sphenoparietal suture
ossification - at the 2 centres near the parietal eminence in utero at 2nd month, fuse together in utero
Variation
- accessory intraparietal suture
- frontal and temporal bone meet together so the parietal and sphenoid bone cannot articulate
The parietal eminence and temporal lines at each parietal bone
fracture of parietal bone
enlarged parietal foramina
craniosynostosis
Temporal bone
Neurocranium
Irregular bone
squamous, petrous, tympanic, mastoid parts styloid process, mandibular fossa, zygomatic, mastoid process
meets with occipital at occipitomastoid suture and pertooccipital sychondrosis
parietal bone at squamous and parietomastoid suture
sphenoid bone at sphenosquamous suture an sphenopetrosal synchondrosis
zygomatic at the temporozygomatic suture
mandible at the temporomandibular suture
middle meningeal artery, posterior auricular artery and stylomastoid artery
inferolateral aspects of the cranium. contain the middle and internal ear.
Parts: squamous, petrous, tympanic, mastoid part and styloid process
Landmarks: mastoid process, tegmen tympani, arcuate eminence, jugular fossa, supramastoid crest and postglenoid tubercle
ossification -
squamous part in utero at 2nd month
tympanic 1-4 centre appear in utero in the 3rd month
petrous and mastoid part appear in utero in the 5th month
styloid process - 2 centres of it shown at the time of birth
tympanic and squamous fuse at the time of birth and the petrous, mastoid and styloid fuse with rest at the 1st year of birth
Variation -
longer styloid process
foramen tympanicum - foramen of Huschke, present along the bony part of the external acoustic meatus.
frontal and temporal may bind so parietal and sphenoid bones don’t meet each other
sexual dysmorphism so more prominent in males
fracture of the bone
osteitis deformans - Paget disease of the bone - disrupts normal cycle of bone renewal - weakened and deformed bone
osteomyelitis of the bone- infection of the bone
mastoiditis inflamed bone
craniosynostosis
zygomatic arch dysplasia
Axis
C2 irregular bone
Dens, vertebral body, laminae, pedicles, superior and inferior articular process and transverse and spinout processes
Atlas and C3
vertebral artery
this is also called epitropheus
known as atypical because it has dens
Parts: dens, laminae, pedicles, superior and inferior articular processes and transverse spinous processes
Surfaces - inferior intervertebral surface, inferior anular epiphysis and vertebral arch
Landmarks- apex of dens, inferior vertebral notches, superior and inferior articular facets and anterior and posterior articular facets of dens
meets with C3 at intevertebral symphysis joint and zygapophyseal joints
atlas at both median and lateral atlantoaxial joints
Ossification - 5 centres
vertebral body - 4-5 months in utero
R+L half of the vertebral arch with one centre in each during 2nd month in utero
R+L halves of the dens with one centre in each at 4-5 months in utero
sides of den fuse before birth and then this fuses to vertebral body at 3-4 years
R+L halves of the vertebral arch fuse with each other during 3-4 years which then fuse with the body at 4-6 years
Variation -
- apex of the den not fuse with the rest of the den but exist as an accessory bone known as ossiculum terminale
dens no fuse with vertebral body and exist as accessory bone known as os odontoideum
dens present in the bifid form
difficult to palpate as it lies deep within the nuchal ligament
fracture osteoporosis spinal stenosis scoliosis hypoplasia of axis dislocation of the 2 joints spina bifida block vertebra
Sagittal suture
parietal bones fibrous suture
Lambdoid suture
lambda shaped along posterior aspect of the cranium -
