HNN Topic 2 - Vasculature of the Brain and Meninges Flashcards
What is the clinical significance of the sphenoid emissary vein
Root of spread of infection from the upper teeth to the cranial cavity
Describe the structural differences between normal veins and the dural venous sinuses
The dural venous sinuses lack smooth muscle and valves
Define dural reflections
Areas where infolding of the dura mater occurs, partitioning the cranial cavity
Describe the connections of the dural venous sinuses
- The superior and inferior sagittal sinuses anastomose with the straight sinus at the confluence of the sinuses - The transverse sinus comes from the confluence and goes on to form the sigmoid sinuses - The sigmoid sinuses drain into the IJV as they leave the cranium via the jugular foramina
Describe the components and drainage of the deep venous system
- Drains the thalamus, hypothalamus, internal capsule, septum pellucidum, choroid plexus, corpus striatum and white matter - Deep cerebral veins = subependymal, medullary - Drain into the trasverse, straight and sigmoid sinuses
Describe the drainage and connections of the cavernous sinus
Cavernous sinus is anterior, receives blood from the ophthalmic vein and empties into the superior and inferior petrosal sinuses which drain into the sigmoid sinuses (-> IJV)
List the branches given off by the vertebral arteries and describe their functions
- Meningeal branch - supplies falx cerebri 2. Anterior and posterior spinal arteries - supplies spinal cord 3. Posterior inferior cerebellar a - supplies cerebellum and pons
Describe the position of the sellar diaphragm
Forms a partial roof over the hypophysial fossa, covers the pituitary fland, aperture for passage of the infundibulum of the pituitary
List the main arteries which supply the brain
- Vertebral arteries 2. Internal carotid arteries
What is the significance of the falx cerebri when considering the dural venous sinuses
The falx cerebri between the L and R cerebral hemispheres (in the longitudinal fissure) contains the superior and inferior sagittal and straight sinuses
Describe the position of the tentorium cerebelli
Between the occipital lobe of the cerebrum and the cerebellum, divides the cranial cavity into supratentorial and infratentorial areas
Describe the features of the arachnoid mater
- Middle layer - Layers of connective tissue, avascular, no innervation - Subarachnoid space underneath, contains CSF - Projections of arachnoid mater into dura (arachnoid granulations) allow CSF to re-enter the circulation via dural venous sinuses
Describe the components and drainage of the superficial venous system
- Primarily drains the cerebral cortex - Cortical veins - superior, middle and inferior groups - Drain into the superior sagittal sinus
Describe the arrangement of the arteries which supply the brain
Terminal branches of the vertebral and internal carotid arteries form an anastomotic circle called the Circle of Willis, which gives off branches to supply the majority of the brain
Which anatomical landmark marks the confluence of the sinuses
Internal occipital protuberance
Describe the path of the internal carotid arteries
- Move superiorly through the neck in the carotid sheath 2. Enter brain via foramen lacerum (carotid canal), 3. Pass anteriorly through cavernous sinus 4. Give off branches 5. Continue as middle cerebral arteries
Describe the function of the meninges
- Provide supportive framework for cerebral and cranial vasculature - Act with CSF to protect the CNS from mechanical damage
Describe the features of the pia mater
- V thin, tightly adhered to surface of brain/spinal cord - Follows contours of brain gyri/sucli - Highly vascularised, BVs perforate through to supply the underlying neural tissue - Anchored to brain by processes of astrocytes (glial cells) - Unicellular membrane
List the branches given off by the internal carotid arteries and describe their functions
- Ophthalmic artery - supplies structures of the orbit 2. Posterior communicating artery - connects the circle of Willis posteriorly 3. Anterior choroidal artery - supplies structures in the brain responsible for motor control and vision 4. Anterior cerebral artery - supplies anterior parts of the cerebrum
List the dural reflections
- Falx cerebri 2. Tentorium cerebelli 3. Cerebellar falx 4. Sellar diaphragm
Describe the venous drainage of the dura mater
Dural venous sinuses -> IJV
Describe the arterial supply of the dura mater
- Anterior meningeal artery - branch of ethmoidal a 2. Middle meningeal artery - branch of maxillary a 3. Posterior meningeal artery - branch of ascending pharyngeal a 4. Accessory meningeal artery - branch of maxillary a
List the layers of the dura mater
- Endosteal/periosteal layer 2. Meningeal layer
Describe the path of the vertebral arteries
- Ascend the posterior aspect of the neck through the transverse foramen of the cervical vertebrae 2. Enter the cranial cavity through the foramen magnum 3. Give off branches 4. Converge to form the basilar artery which gives of branches to supply the pons and cerebellum 5. Basilar artery terminates by bifurcating into posterior cerebral arteries
Describe the location of the dural venous sinuses in relation to the layers of the meninges
Between the outer (endosteal/periosteal) and inner (meningeal) layers of the dura mater
Describe the endosteal layer of the dura mater
Lines the inner surface of the cranial bones, only present around the brain (not in the vertebral column)
Describe the location of the dura mater
Outer layer of the meninges, lies directly under the bones of the skull and the vertebral column
Describe the position of the cerebellar falx
Partially divides the cerebellar hemispheres
List the dural venous sinuses
Superior sagittal sinus, inferior sagittal sinus, straight sinus, transverse sinus, sigmoid sinus
Describe the features of the dura mater
Thick, tough, inelastic
Describe the origins of the vertebral arteries
L and R from subclavian artery
List the layers of the meninges
- Dura mater 2. Arachnoid mater 3. Pia mater
Describe the position and attachment of the falx cerebri
Between L + R hemispheres of the cerebrum in the longitudinal fissure Attached anteriorly to the crista galli of the ethmoid bone and posteriorly to the tentorium cerebelli
Describe the general venous drainage of the brain
Veins empty into dural venous sinuses which eventually empty into the internal jugular veins
Describe the meningeal layer of the dura mater
Lines the endosteal layer, only layer present in the vertebral column
Where do the internal carotid arteries originate?
At the bifurcation of the L and R common carotid arteries, at the level of C4
