Lecture 6: Skull Flashcards
Optic Canal
CNII (Optic Nerve)
Superior Orbital Fissure
CNIII (Oculomotor)
CNIV (Trochlear)
CNVI (Abducens)
CNV–> V1 branch
Foramen Ovale
V3 –> Mandibular branch of the trigeminal nerve
Foramen Spinosum
Middle Meningeal Artery
Internal Carotid Artery
Enters the cranial vault via the CAROTID FORAMEN, passing through the BONY CANAL and entering into the calvaria via the CAROTID CANAL.
CNVII (Facial)
Enters the INTERNAL AUDITORY MEATUS.
Exits via the STYLOMASTOID FORAMEN.
CNVIII (Vestibulocochlear)
Enters in the INTERNAL AUDITORY MEATUS.
Exits via the EXTERNAL AUDITORY MEATUS.
Jugular Foramen
CNIX (Glossopharyngeal)
CNX (Vagus)
CNXI (Spinal Accessory)
***All 3 exit from here.
CNXI (Accessory)
Enters via the FORAMEN MAGNUM.
Joins the cranial branches and exits via the JUGULAR FORAMEN.
CNXII (Hypoglossal)
Exits via the HYPOGLOSSAL CANAL.
What space harbors the bulk of the CSF?
Subarachnoid
What two major pairs of arteries provide blood supply to the brain?
Right and Left Internal Carotid Artery.
Right and Left Vertebral Arteries.
Where do the common carotid arteries bifurcate?
In the neck, just below the angle of the jaw.
What areas does the ECA supply?
face, scalp, and meninges covering the brain
Describe the path of the ICA
They ascend and travel through the carotid canal, enter the cranial vault alongside the cavernous sinus. At this point , they make a hairpin turn backwards and continue on as the middle cerebral artery and anterior cerebral arteries.
What is the first branch of the ICA?
The ophthalmic arteries, which branch off near the apex of the hairpin turn.
Where do the right and left vertebral arteries originate from?
Subclavian arteries.
Describe the path of the vertebral arteries
They enter the vertebral foramen bilaterally at the C6 level and travel upward through these foramen, entering the skull via the foramen magnum.
The two join at the junction of the medulla and pons to form the BASILAR ARTERY.
What can occur if there is head trauma in the region of the middle meningeal artery?
Bleeding into the epidural space can occur.
**This is a neurological and neurosurgical emergency with death occurring within a few hours if undiagnosed and untreated.
Why is the circle of willis important?
It provides the possibility for collateral flow if one or more of the four major arteries supplying the brain are obstructed or occluded.
What composes the Circle of Willis?
It consists of the posterior cerebral arteries connected to the internal carotid arteries via the posterior communicating arteries.
The anterior A1 segment of the anterior cerebral arteries and the anterior communicating artery complete the Circle of Willis.
What can result of you occlude any of the major sinuses of the brain?
Seizures, tissue injury, or blockage of the CSF circulation.
What allows communication between the 3rd and 4th ventricles?
Cerebral Aqueduct (Aqueduct of Sylvius)
What allows communication between the lateral ventricles and the midline third ventricle?
Interventricular Formamen of Monro.
Where and how is CSF created?
It is made in the choroid plexus by specialized epithelial cells that line the lateral, third and fourth ventricles.
Describe the path of CSF
- Escapes the lateral ventricles into the third via the foramen of mono.
- Enters the fourth via the aqueduct of Sylvius.
- Leaves the fourth via the foramen of MEgendie and Luschka.
- Once in the subarachnoid space, some of the CSF circulates down around the spinal cord where 10% is reabsorbed at the egress point of the nerve roots.
- The bulk of the CSF (90%) is reabsorbed into the venous sinuses via the arachnoid granulations.
What are the arachnoid granulations?
Outpouchings of the arachnoid that protrude into the large venous sinuses.
What is the rate of CSF production?
~20mL/hr
Obstructive Hydrocephalus
Buildup of intraventricular CSF caused by obstruction of the outflow pathways between the lateral and third and third and fourth ventricles.
True or False: Brain capillaries contain fenestrations?
False; Systemic capillaries do though.
What creates the BBB?
Tight junctions between capillary endothelial cells.
What is the function of astrocytes?
They provide an additional layer of protection to the brain by preventing the direct access of substances in the blood from reaching neurons.
Describe the Choroid Plexus
It is created by an outpouching of capillaries and the pia mater into the ventricular space.
It sandwiches capillary blood vessels between layers of the arachnoid membrane and the pia mater.
**There is an additional layer of cells that line the outpouchings of the choroid plexus.
Describe the extra layer of cells found in the choroid plexus.
These cells are contiguous with the cells lining the ventricular walls. They are called ependymal cells in the ventricles but are called choroid epithelium when they line the choroid outpouchings.
How can you distinguish between ependymal cells and choroid epithelium?
Ependymal cells have normal fenestrations but choroid epithelial cells are found in very close approximation to one another. This prevents passage of particles through the choroid plexus into the ventricular CSF.
What are the circumventricular organs? (Brain structures without BBB)
- Pineal Gland
- Area Postrema
- Sublomical Organ?
- Posterior Pituitary (Neurohypophysis)
- Median Eminence
- Organum Vasculosum of the Lamina Terminals (OVLT)
The function of several of these areas is unknown, but the organum vasculosum and neurohypophysis are well known to monitor and regulate electrolyte balance and several important hormones, respectively.
