OCB04-2002 Flashcards
What is the main function of the cranium?
Protect brain and sensory organs
What are the two main parts of the cranium?
Neurocranium
Viscerocranium
How many bones make up the neurocranium?
8
Which bones make up the neurocranium?
Frontal
Ethmoidal
Sphenoidal
Occipital
2 temporal
2 parietal
What are the three regions of the neurocranium?
Calvaria
Basicranium
Intracranial region
How many bones form the viscerocranium?
14
Which bones form the viscerocranium?
2 maxilla
2 inferior nasal conchae
2 zygomatic
2 palatine
2 nasal
2 lacrimal
Mandible
Vomer
What is the only movable joint in the skull?
Temporomandibular joint
Describe the basic parts of the sphenoid.
Pair of lesser wings superiorly
Pair of greater wings inferiorly
Body
Medial and lateral pterygoid plates inferiorly on each side
What makes up the nasal septum?
Perpendicular plate of ethmoid bone
Vomer
What are the two parts of the temporal bone called?
Squamous part (external)
Petrous part (internal)
Why is the petrous part of the temporal bone so hard?
Protect the inner ear/cochlea
What region of the skull is most easily fractured and why?
Pterion
Where many skull bones meet, very thin
What is the name of the point where the temporal, parietal and occipital bones meet?
Asterion
What do the frontal bones form?
Forehead
Roof of orbits
What do the parietal bones form?
Lateral walls and roof of cranium
What do the occipital bones form?
Posterior region of skull
What do the temporal bones form?
Inferolateral walls of skull
Part of intracranial region
What is the function of the sphenoid bone in the skull?
Unites cranial and facial bones
What bones does the sphenoid articulate with?
Every other cranial bone
Maxilla, palatine, zygomatic and vomer bones
What do the ethmoidal bones form?
Anteromedial floor of cranium
Roof of nasal cavity and part of nasal septum
Part of medial wall of orbits
What shape are the palatine bones?
L-shaped
What do the palatine bones form?
Part of hard palate, nasal cavity and eye orbit
Which bones form the central part of the viscerocranium?
Maxillae
Which are the smallest bones in the skull?
Lacrimal bones
What do the lacrimal bones form?
Part of medial walls of orbits
Why does the lacrimal bone have a groove?
Passageway for tear ducts to drain into nasal cavity
What do the nasal bones form?
Bridge of nose
What does the vomer form?
Inferoposterior part of nasal septum
What is another term used for the inferior nasal conchae?
Turbinates
Where are the inferior nasal conchae located?
Lateral wall of nasal cavity
What is the function of the inferior nasal conchae?
Creates turbulence in inhaled air => slows air so it can be warmed and filtered
What bone are the superior and middle nasal conchae part of?
Ethmoid
Describe the location of the mandibular foramen.
Inner/medial side of ramus, partly covered by the lingula
What passes through the mandibular foramen?
Inferior alveolar/dental nerve and associated vessels
When do motor nerves to the mylohyoid and anterior belly of the digastric branch off the IAN?
Just before the IAN enters the mandibular foramen
What emerges from the mental foramen?
Mental nerves (supply skin and mucosa of this area/chin)
What are the four main air sinuses in the skull?
Frontal
Ethmoidal
Maxillary
Sphenoidal
Describe an air sinus.
Spaces containing air and mucus which drain out through the nose/nasopharynx
Why does maxillary sinusitis usually need treatment (unlike the other sinuses)?
Has to drain against the force of gravity to reach nose so harder to clear infections (treat with antibiotics)
What are the functions of skull sutures?
Allow movement during birth
Act like an expansion joint to allow bones to enlarge evenly as brain grows
What type of joint is a suture?
Fibrous/synarthrosis
What are the four main fontanelles?
Anterior fontanelle (between frontal and parietal)
Anterolateral fontanelle (between frontal, parietal, sphenoid and temporal)
Posterolateral fontanelle (between parietal, temporal and occipital)
Posterior fontanelle (between parietal and occipital)
What is the bregma point?
Where the coronal and sagittal sutures meet (frontal and parietal)
What is the lamda point?
Where the sagittal and lambdoid sutures meet (parietal and occipital)
How many cervical vertebrae are there?
7
What are the functions of the cervical spine?
Support neck structures
Allow movements of head
What head movements are enabled by the cervical spine?
Flexion (forward tilt) or extension (backward tilt)
Lateral flexion (tilt side to side)
Rotation (turn side to side)
Which is the largest cervical vertebra with the longest vertebral prominence?
7th
What extra feature do the cervical vertebrae have (compared to other vertebrae)?
Transverse foramen
What is the function of the transverse foramina?
Allow passage of vertebral arteries and veins
Which of the cervical vertebrae are specialised?
C1 “atlas”
C2 “axis”
What is different about the first cervical vertebra?
(Atlas) has no vertebral body or spinous process
What is different about the second cervical vertebra?
(Axis) has a “dens” to articulate with the facet of the atlas
What are the ligaments important in preventing neck dislocation of first two cervical vertebrae?
Cruciform ligament (forms a cross over dens)
Alar ligaments (attach to base of foramen magnum from either side of dens)
What bones make up the anterior cranial fossa?
Frontal, ethmoid and lesser wings of sphenoid
What bones make up the middle cranial fossa?
Greater wings and body of sphenoid and petrous part of temporal bone
What bones make up the posterior cranial fossa?
Temporal and occipital
What is the sella turcica?
Saddle-like prominence on the superior surface of the body of the sphenoid
Crosses midline and contains pituitary gland
Which cranial nerve runs over the pituitary gland?
C.II optic nerve
What are the three layers of the meninges called?
Dura mater
Arachnoid mater
Pia mater
Which of the meninges cannot be seen with the naked eye?
Pia mater
Describe the dura mater.
Outermost protective layer of meninges
Made of collagen fibres
Describe the arachnoid mater.
Middle layer of meninges
Web-like and delicate
Describe the pia mater.
Innermost layer of meninges
Continuous with surface of brain/spinal cord
What is the middle meningeal artery and its significance?
Largest of three paired arteries supplying the meninges
Branch of maxillary artery (branch of external carotid)
Runs beneath pterion where skull is easily fractured so may cause extradural haemorrhage
What does the middle meningeal artery pass through in the intracranial region?
Foramen spinosum (to supply dura mater and calvaria)
What is the corpus callosum?
Large, C-shaped nerve fibre bundle found beneath cerebral cortex
Connects left and right cerebral hemispheres
White matter
What is the septum pellucidum?
Membrane separating the anterior parts of the lateral ventricles
What is the falx cerebri?
Fold of dura mater in longitudinal fissure
Separates cerebral hemispheres
What is the falx cerebelli?
Fold of dura mater separating the cerebellar hemispheres
What is the tentorium cerebelli?
Extension of dura mater separating the cerebellum from inferior portion of occipital lobes
What is the crista galli?
Anterior attachment for the falx cerebri
Part of ethmoid bone
What are dural venous sinuses?
Spaces between periosteal and meningeal layers of dura mater containing venous blood
No valves
What are the two layers of the dura mater called?
Periosteal
Meningeal
Name the main dural venous sinuses.
Superior and inferior sagittal
Straight
Transverse
Cavernous
Superior and inferior petrosal
Sigmoid
Where does the blood in the dural venous sinuses come from and drain into?
Mostly from brain and cranial cavity
Drains via internal jugular veins
What structures pass through the cavernous sinus?
Oculomotor nerve (III)
Trochlear nerve (IV)
Ophthalmic nerve (V1)
Maxillary nerve (V2)
Carotid (internal)
Abducens nerve (VI)
What forms the boundaries of the cavernous sinus?
Anterior = superior orbital fissure
Superior = meninges of clinoid process
Posterior/inferior = petrous temporal
Medial/inferior = sphenoid
Lateral = meninges of middle cranial fossa
Where is the pterygoid vein plexus located and why is this significant?
Just behind molar region and connects with cavernous sinus
Infections from oral cavity could enter plexus and potentially into the brain due to lack of valves in this area
What is the Circle of Willis and why is it beneficial?
Arterial blood supply to brain formed by anastomosing of internal carotids and vertebral arteries (basilar artery)
Allows blood to cross midline in case of blockages
What are the communicating arteries?
Connections between anterior, middle and posterior cerebral arteries of the Circle of Willis
The blockage of which artery is the most common cause of strokes and why?
Middle cerebral artery
Supplies basal ganglia (involved in motor control)
Which artery do the anterior and middle cerebral arteries branch from?
Internal carotid
Which artery does the posterior cerebral artery branch from?
Basilar
Where do the vertebral arteries arise from?
Subclavian artery at the level of C6
What gives the basilar artery its name?
Passes over the basilar pons
What arteries join to form the basilar artery?
Vertebral
What is the clivus?
Sloping portion of occipital where the basilar pons lies
What is another name for the great cerebral vein?
Vein of Galen
What is the confluence of sinuses?
Where the superior sagittal, straight and transverse sinuses meet posteriorly
Does the inferior sagittal sinus pass above or below the corpus callosum?
Above
What forms CSF?
Choroid plexus in ventricles
Where does CSF exit the ventricular system?
Openings in 4th ventricle into the subarachnoid space (firstly cisterna magna behind cerebellum)
