L12: Brain and Meninges Flashcards
What are the major parts of the brain?
- Cerebrum - Cerebellum - Brainstem
What separates the hemispheres from each other? What holds them together?
- Separated by falx cerebri at the longitudinal fissure - Held together/ connected by corpus callosum
What separates the cerebellum from the remaining brain structures? What unites the two hemispheres of the cerebellum?
- Tentorium cerebelli lies above the cerebellum, separating it from the cerebrum - Vermis unites the two hemispheres
What are the parts of the brainstem?
- Midbrain - Medulla oblongata and pons
What arteries supply blood to the brain?
- Vertebral arteries - Internal carotid arteries
Course of vertebral arteries. Branches
- Vertebral artery is first branch off of subclavian. - Travels through transverse foramina of cervical vertebrae - Enters into the cranium through the foramen magnum. - Gives off posterior inferior cerebellar artery laterally, anterior spinal artery, posterior spinal artery - Unites at lower border of pons to form the basilar artery
Course and branches of basilar artery.
- Arises from vertebral artery at lower border of pons - Lies in median groove of the pons - Gives rise to: Anterior inferior cerebellar arteries Pontine arteries Superior cerebellar arteries Posterior cerebral arteries (terminal branches)
What are the major arteries that supply blood to the cerebellum?
- posterior inferior cerebellar arteries (PICA) from vertebral arteries - anterior inferior cerebellar arteries (AICA) from basilar artery - superior cerebellar arteries (SCA) from basilar artery
Course and branches of internal carotid arteries.
- Common carotid branches into internal and external carotids at the superior level of thyroid cartilage (~ C5). - Internal carotid arteries enter the skull through the carotid canal and gives rise to its branches: Posterior communicating Middle cerebral Anterior cerebral – become joined with anterior communicating artery and disappear in median longitudinal fissure
Draw the Circle of Willis

What is the pontomedullary junction?
- Area where vertebral arteries join and become the basilar artery
List 3 cranial meninges. Describe
- Dura mater (tough, outer layer) - Arachnoid mater (thin, avascular intermediate layer) - Pia mater (vascular inner layer)
How is dura mater different in cranium than in spinal canal?
- Called cranial dura in cranium as it has two layers. - External layer = external periosteal layer (aka endocranium) continuous with periosteum - Internal layer = internal meningeal layer continuous at foramen magnum with spinal dura
What are dural folds? List dural folds present and explain.
- Dural folds refers to internal layer of dura that separates from external periosteal layer to form folds/partitions separating regions of brain. Falx cerebri: lies in longitudinal fissure separates two cerebral hemispheres Tentorium cerebelli: separates occipital lobe from cerebellum Falx cerebelli: partly separates the cerebellar hemispheres Diaphragma sellae: circular sheet of dura suspended bw ant and clinoid processes of sphenoid bone forming roof over hypophyseal fossa allows hypophyseal stalk/infundibulum to penetrate through.
Where is CSF generated? What are the chambers of the ventricular system of the brain?
- Chroid plexus in the ventricles - Chambers: 2 x lateral ventricles (in each cerebral hemisphere) 3rd midline ventricle 4th inferior posterior ventricle
Function of CSF?
- Cushioning brain and spinal cord - Transportation of chemicals - Clearing waste
Explain CSF circulation.
- CSF generated in lateral ventricles travel to 3rd ventricles via interventricular foramen of Monro - CSF generated and accumulated in 3rd ventricle (from lateral ventricles) travel to 4th ventricle via cerebral aqueduct of Sylvius - CSF generated and accumulated in 4th ventricle (from lateral and 3rd ventricles) travel to subarachnoid space via median aperture (aka foramen of Magendie) or lateral apertures (aka foramina of Luschka) - CSF moves into subarachnoid space in spinal cord in cranium
Large fissures in brain.
- Lateral fissure (sulcus of Sylvius) is large sulcus that separates frontal/parietal lobes from temporal - Central fissure/sulcus separates frontal from parietal lobes
What is the insula?
- Large portion of cerebral cortex folded deep within lateral sulcus.
Through what fissures do branches from the internal carotid travel?
- Middle cerebral arteries travel through lateral fissures - Anterior cerebral arteries travel through longitudinal fissures
What is the major blood supply to the dura?
- Minor by meningeal arteries (anterior and posterior) - Major by middle meningeal artery (from maxillary artery branch of external carotid artery)
Over what cranial landmark does one find the middle meningeal artery?
- Pterion
Why would injury to pterion be dangerous? What type of bleed can it lead to?
- Pterion overlies the middle meningeal artery, which overlies and supplies blood to the dura. - It could lead to an epidural bleed/hematoma.
What are venous sinuses of brain? List them and explain where they are located.
- Endothelial lines spaces between the periosteal and meningeal layers of the dura. Large veins from around the brain empty here and blood returned to venous circulation 1.) superior sagittal sinus: upper border of falx cerebri 2.) inferior sagittal sinus: inferior edge of falx cerebri 3.) straight sinus: junction of falx cerebri and tentorium cerebelli 4.) transverse sinuses: continuation of superior and straight sinuses 5.) sigmoid sinuses: at petrous bone, transverse sinuses end and become sigmoid sinuses which empty at jugular foramen 6.) occipital sinus: lies in attached border of falx cerebelli 7.) cavernous sinuses: located bilaterally on each side of sella turcica 8.) sphenoparietal sinuses: course along lesser wing of sphenoid bone 9.) superior petrosal sinuses: stretch between cavernous and transverse sinuses 10.) inferior petrosal sinuses: commence at cavernous sinus and drain into jugular foramen - Confluence of sinuses: junction between superior sagittal, straight, occipital and transverse is at the confluence of sinuses located at the internal occipital protuberance