Osteology Of Skull Flashcards
What are the 2 parts of the skull
Neurocranium and viscerocranium
What is neurocranium
The bony covering of the brain and the membranous covering (the cranial meninges)
Contents of the neurocranium
Proximal part of the cranial nerves and vasculature of the brain
The 2 Parts of the neurocranium
- A dome-like roof called the calvaria or skull cap
- A floor or cranial base called the basicranium.
In adults the neurocranium is formed by how many bones
8 (four singular bones and two bilateral paired bones)
What are the 8 bones of the neurocranium
Singular (SOFE)
-Sphnenoidal
-Occipital
-Frontal
-Ethmoidal
Bilaterally paired (PT)
-Parietal
-Temporal
Viscerocranium comprises of what bones
Fascial bones (forms the anterior part of the cranium). It consists of bones surrounding the mouth (upper and lower jaw), nasal cavity and most of the orbits (eye sockets or orbital cavities).
How many bones make up the viscerocranium
15 irregular bones (3 are singular and 6 are bilaterally paired)
What are the 3 singular viscerocranium bones
VEM
- Vomer
- Ethmoidal
- Mandible
What are the 6 bilaterally paired viscerocranial bones
My Inner Zip Pointed Lateral North
1. Maxillae
2. Inferior nasal conchae
3. Zygomatic
4. Palatine
5. Lacrimal
6. Nasal bones
What viscerocranial bones house the teeth
Maxillae and mandible
What viscerocranial bone forms the greatest part of the upper fascial skeleton, forms the skeleton of the upper jaw and is fixed to the cranial base
Maxillae
What forms the skeleton of the lower jaw
Mandible
Why is mandible moveable
Because it articulates with the cranial base at the temporomandibular joints (TMJs)
What makes up the anterior or frontal or fascial part of the
Frontal bone, zygomatic bones, orbits, nasal region, mandible and maxillae
What bones do the frontal bone articulate with
Nasal, zygomatic, ethmoid, sphenoid, lacrimal.
The alveolar process of the maxillae includes
The tooth sockets called the alveoli and it houses the maxillary teeth.
What bones do the maxillary bones articulate with anteriorly and laterally
Frontal bone and zygomatic bone
Shape of the mandible
U-shaped
The alveolar process of the mandible supports the
Mandibles teeth
The 2 parts of the mandible
Body (horizontal part)
Ramus (vertical part)
Location of the mental foramina
Inferior to the 2nd premolar teeth
What passes through the mental foramina
Mental nerves and vessels
Infraorbital foramen is located where and what passes through it
On the maxilla
Infraorbital nerve and vessel
What passes the supraorbital foramen
Supraorbital nerves and vessels
What passes the zygomaticofascial foramen
Zygomaticofascial nerve
What is injury to the supercilliary arches
Check slide
What is malar flush
Check slide
The superior aspect of the skull is called
Calvaria or skull cap
What are the bones forming the e superior part of the skull
Frontal bone (unpaired)
Parietal bone (paired)
Occipital bone (unpaired)
The frontal bone articulates with the parietal bones at the what
Coronal suture
The two parietal bones articulate with each other at what suture
Sagittal suture
The parietal bones articulate with the occipital bone at what suture
Lambdoid suture
The most superior part of the skull that is near to the midpoint of the sagittal bone is what
Vertex
The intersection between the CoronAl suture and the sagittal suture is called
Bregma
The junction between the sagittal suture and the lambdoid suture is called the
Lambda
What passes the parietal foramen on the parietal bones
Emissary veins
The region of the skull between the two parietal foramina where the closure of the sagittal suture usually begin
Obelion
What is depressed fracture of the calvaria
Check your slide
What is the most frequent type of calvarial fracture
Linear calvarial fracture
Types of calvarial fracture
Depressed fracture
Linear calvarial fracture
Comminuted fracture
Contrecoup or countercoup fracture
Basilar fracture
Obliteration of fracture begins at where
Bregma and continues sequentially in the sagittal, coronal and lambdoid suture
Obliteration of the sutures between bone of the calvaria begin between what age
Begins at age 30 and 40 years on the internal surface and approximately 10 years later on the external surface
The halves of the frontal bone of a new born is separated by
Frontal suture
The frontal and parietal bones of a new born are separated by
Coronal suture
The maxillae of a newborn baby are separated by
Intermaxillary suture
The two halves of the mandible of a new born are separated by
Mandibular symphysis
The mandible of a newborn begins fusion during ————— year and ends at what year ———-
1st year
2nd year
At birth, there is mastoid and styloid process. True or false
False
The mastoid process gradually forms at what year
1st year
What are frontanelles
They are membranous intervals that separates the bones of the calvaria of a newborn infant
How many frontanelles are present during infancy; name them
6
Posterior
Anterior
Paired sphenoidal
Paired mastoid frontanelles
What is the largest frontanelle
Anterior frontanelle
What is the shape of the anterior frontanelle
Diamond or star shaped
Why are the boundaries of the anterior frontanelle
Anteriorly by: two halves of the frontal bone.
Posteriorly: parietal bones.
Location of the anterior frontanelle
Junction of sagittal, coronal and frontal sutures (the future Bregma).
When does the anterior frontanelle close
18th month of age (the surrounding bones have fused and the anterior frontanelle os not clinically palpable)
When does the frontal bone begin to fuse
In the 2nd year
When is the frontal suture obliterated
The 8th year
In ~ 8% of people, the remnant of the frontal suture persists an what?
Metopic suture
What is the shape of the posterior frontanelle?
Triangular shape
Boundary of the posterior frontanelle
Anteriorly: the parietal bones
Posteriorly: the occipital bone
Location of the posterior frontanelle
The junction of the lambdoid and sagittal suture (future lambda).
When does the posterior frontanelle close
Begins closure during the first few months after birth and the 1st year. It’s small and no longer clinically palpable.
Location of the sphenoid and mastoid fontanelles
Overlain the temporal muscle
When does the sphenoid and the mastoid frontanelle fuse
During infancy
The two maxillae and nasal bones usually don’t fuse. True or false
True
What makes the calvaria of cranial bones change shape (mold) during child birth?
The softness of their cranial bones and the loosed connections at their sutures and frontanelles.
What happens to the calvaria during the passage of fetus through the birth canal?
The frontal bone becomes flat, the occipital bone is drawn out and the parietal bones slightly overrides the other.
What allows the cranial bones resist forces that would produce fractures in the adults
The resilience of the cranial bone
When does the shape of the calvaria return back to normal after undergoing molding.
Few days after birth
What permits the calvaria to enlarge during infancy and childhood
The fibrous suture
The increase in the size of the calvaria is greatest at what age
During the first two years of life (the period of the most rapid brain development).
The normal capacity of the calvaria increases for how many years
15-16 years
After the increase is size of the calvaria after the first 2 years then the next 15-16 years, the calvaria usually increase in size for another 3-4 years because of what
Bone thickening
What is craniosynostosis
Premature closure of the cranial sutures
Premature closure of the sagittal suture (in which the anterior frontanelle is small and results in a long wedge-shaped cranium) leads to
Scaphocephaly
Premature closure of the coronal or lambdoid suture (occurs in one side only) results in
Plagiocephaly
Premature closure of the coronal suture results in a high,,tower-like cranium called
Oxycephally or turricephaly
Oxycephaly or turricephaly is most common in
Females
Premature closure of the sutures usually don’t affect brain development, True or false
True
Composition of the lateral part of the neurocranium
Frontal, parietal, temporal, occipital and sphenoid.
What are the bones forming the visible part of the facial or viscerocranial
Zygomatic, nasal, mandible and maxillae
What are the of main features of the neurocranium
Temporal fossa, external auditory meatus and mastoid process of temporal bone.
What are the main features of the viscerocranium.
Infratemporal fossa, zygomatic arch, lateral aspect of mandible and maxilla
Where is the pterion on
The junction where the frontal, parietal, temporal and greater wing of sphenoid bone meet. It’s usually indicated by a H-shaped formation of sutures
Why is pterion area on important?
Because it overlies the middles meninges artery
What happens when the pterion becomes fractured
It can rupture the anterior branch of the middle meningeal artery which can lead to hematoma and this hematoma can exert pressure on the underlying cerebral cortex. If the rupture is left untreated, it can cause hemorrhage and lead to death in a few hours.
Boundaries of the infratemporal fossa
Superiorly: inferior surface of the greater wing of the sphenoid bone
Inferiorly: Superiorborder of the body of the mandible
Anteriorly: posterior surface of the maxilla.
Posteriorly: Styloid process and external auditory meatus
Laterally: zygomatic arch and ramus of mandible.
Medially: lateral pterygoid plate of the sphenoid bone.
The point where the superior temporal line cuts the coronal suture is called what
Stephanion
The junction (wheee they meet) between these three sutures: parietomastoid, occipitomastoid and lambdoid suture is called the
Asterion
What bones make up the posterior part of the skull
Occipital bone
Parts of parietal bones
Temporal bones(mastoid part)
The most prominent part of the external occipital protuberance is called the
Inion
What is the distance of the inferior Michael lines from the superior Michael lines
1 inch (2.5cm)
Along the lambdoid suture are what bones
Sutural or wormian bones
How many depressions/fossae do we have on the internal surface of the cranial base
3
Anterior, middle and posterior cranial fossae
Which cranial fossae is at the highest level and the shallowest
Anterior cranial fossa
What sits in the floor of the anterior cranial fossa
Frontal lobe of the cerebral hemispheres
What sits on the floor of the lateral portion of the middle cranial fossa
Temporal lobe
What sits on the midline of the middle cranial fossa
Pituitary gland or hypophysis
What is the lowest/ deepest part of cranial base
Posterior cranial fossa
What sits on the anterior portion of the floor of the posterior cranial fossa
Brainstem
Brainstem is made up of
Midbrain, pons and medulla oblongata
What occupies the rest of the posterior cranial fossa
Cerebellar hemispheres
The occipital lobe sits on the floor of the posterior cranial fossa. True or false
False
The cerebellum sits on the floor of the posterior cranial fossa. True or false
True
What bones forms the anterior cranial fossa?
Frontal bone in the anterior and lateral directions.
Ethmoidal bone in the middle
The 2 parts of Sphenoid bone in the posterior part
The part of the frontal bone in the anterior cranial fossa
Orbital surface
What are the two parts of sphenoid bone in the anterior cranial fossa
Jugum
Lesser wing of sphenoid
The cribiform plate of the Ethmoid bone has numerous tiny foramina that transmits what from the olfactory area of the nasal cavity to the olfactory bulb of the brain
Olfactory nerve (CN1)
What does the frontal cecum transmit (when open) from the nose to the superior sagittal sinus?
What is the clinical importance or this?
Emissary vein
Infections from the nose and other areas can be transmitted to the meninges and the brain.
What two structures passes through the optic canal as they exit the cranial cavity to enter the orbit?
Optic nerve (CN II) and ophthalmic artery.
The optic canals are usually included in the middle cranial fossa, true or false
True
What is the shape of the middle cranial fossa
Butterfly-shaped
What separates the anterior cranial fossa from the middle cranial fossa both laterally and centrally
Laterally: sphenoidal crest
Centrally: sphenoid limbus
What forms the posterior boundary of the jugum and anterior border of the prechiasmatic sulcus
Sphenoid limbus
Prechiamatic groove of bounded Posteriorly by
Tubercullum sella
What bones form the middle cranial fossa
Parts of the sphenoid bone
Parts of the temporal bone
The part of the sphenoid bone that forms the middle cranial fossa are
Sella turcica (part of the body of the sphenoid bone)
Greater wing of the sphenoid bone laterally
How many parts of sella turcica do we heave, name them
3
Tuberculum sella (anterior wall)
Hypophyseal fossa (houses the pituitary gland)
Dorsum sella (Posterior wall)
On each side of the body of the sphenoid are how many foraminas, name them?
4
Superior orbital fissure
Foramen rotundum
Foramen ovals
Foramen spinosum
What passes the superior orbital fissure
Cranial nerves III, IV, VI (occulomor, trochlear, abducens)
Ophthalmic division of trigeminal nerve (V1)
Ophthalmic vein
What passes the foramen rotundum?
Maxillary branch of trigeminal nerve (V2)
What passes through the foramen ovale
Mandibular branch of trigeminal nerve (V3)
Accessory meningeal artery
Lesser petrosal nerve
What passes through the foramen spinosum
Middle meningeal artery
Meningeal branch of mandibular nerve
What are the parts of the temporal bone that forms the middles cranial fossa
Squamous part laterally
Petrous part medially
What grooves are on the Petrous part is the temporal bone l.
Groove for greater and lesser Petrous mAl nerve
I life, foramenmlacerum is closed by the
A cartilage plate and The passage of some meningeal arterial branches and small veins
What forms the boundary between the middle and posterior cranial fossa?
Superior part of Petrous part of the temporal bone laterally and
Dorsum sellae (flat plate of bone) of the sphenoid bone medially.
Which is the largest of the 3 cranial fossa?
Posterior cranial fossa
What does the posterior cranial fossa lodge?
Brainstem (pons, midbrain and medulla oblongata)
What bones form the posterior cranial fossa
Occipital bone and temporal bone
The slope that extends from the Dorsum sella to the foramen magnum is called
The clivus
What passes through the internal acoustic meatus
CN VII and CN VII ( fascial and vestibulocochlear nerve)
What passes through the jugular foramen
CN IX- Glossopharyngeal nerve
CN X- Vagus nerve
CN XI- Accesory nerve
2 venous structures
1. The dura venous sinus from the posterior side of the sigmoid sinus .
2. The inferior Petrousal sinus from the anterior side of the sigmoid sinus
Fusion of the dura sinus and inferior petrousal sinus forms the
Internal jugular vein
What passes through the hypoglossal canal
Hypoglossal nerve CN XII
What passes through the foramen magnum?
-Spinal cord (which is continuous with the medulla oblongata
- Two vertebral arteries
- Spinal contribution of accessory nerve (spinal accessory nerve)
