Week 3 SDL and Practical Session: Brain, meninges and blood supply Flashcards
Explain the significance of the cephalic flexure in terms of anatomical labels
- the axis of the adult brain bends at an angle of about 100* between the midbrain and the diencephalon (the cephalic flexure)
- the terms dorsal and ventral are used as though the flexure did not exist and the CNS was still a straight tube
- therefore, in the spinal cord and brainstem, ‘dorsal’ means posterior, but in the forebrain, ‘dorsal’ means superior
What does grey matter consist of?
consists of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and unmyelinated axons), synapses and capillaries
What does white matter consist of?
- found in deeper tissues of the brain
- contains nerve fibres (axons) covered with myelin, giving its white colour
What is the difference between white and grey matter?
grey matter contains numerous cell bodies and few myelinated axons
What is the cortex made up of?
- grey matter
- makes up 90% of visible surface of brain
- 10mm thick and folded into sulci (grooves) and gyri (ridges) to increase surface area
What is a nucleus?
collection of nerve cell bodies (neurones) within the CNS
What is a tract?
- made of white matter
- bundle of axons connecting nuclei of the CNS
What is a ganglion?
- grey matter
- collection of nerve cell bodies within the PNS e.g dorsal root ganglia and some in the CNS which have a capsule e.g basal ganglia
Which subdivisions of the brain make up the forebrain/ cerebrum?
telencephalon (which contains cerebral hemispheres) and diencephalon (which contains thalamus and hypothalamus)
What is the function of the pre-central gyrus and where is it located?
- located in the frontal lobe
- primary motor cortex is responsible for executing voluntary movements
What is the function of the post-central gyrus and where is it located?
- located in the parietal lobe
- primary sensory cortex is responsible for receiving sensory information
what is the corpus callosum composed of?
white matter - collection of axons that link the neurones
What is the function of the corpus callosum?
enables both sides of the brain to communicate and send signals to eachother
Which structures are made from the telencephalon?
- cerebral cortex
- hippocampus
- amygdala
- olfactory bulb
- basal ganglia
Which structures are made from the diencephalon?
- thalamus
- subthalamus
- hypothalamus
- epithalamus
Which structures are made from the mesencephalon?
tectum cerebral aqueduct tegmentum cerebral peduncles midbrain
What structures are made from the metencephalon?
pons and cerebellum
What structures are made from the mylencephalon?
medulla
What are the 3 meninges that enclose the brain and spinal cord?
- dura mater: thick, dense, fibrous layer of connective tissue composed mostly of collagen
- arachnoid mater - spider-web appearance, thin and transparent
- pia mater - thin, translucent, mesh-like
What 2 layers is dura mater made up of?
- periosteal outer layer
- meningeal inner layer
Where are dural venous sinuses found?
at some sites, the meningeal layer seperates from the periosteum to enclose blood filled spaces into which flows venous blood from the brain
What is the name of the dural septum that extends down between the two hemispheres?
falx cerebri
What is the name of the dural septum that extends between the occipital lobes of the hemispheres and the cerebellum?
tentorium cerebelli
What are the arachnoid villi (also called arachnoid granulations) and what is their function?
- arachnoid villi are small protrusions of arachnoid mater in the outer membrane of dura mater
- they act as one way valves for the flow of CSF into venous blood, and hydrostatic pressure is the main stimulus that causes these valves to open
Which vessel supplies the dura mater?
middle meningeal artery
Describe the course of the internal carotid artery as it enters the skull
- originates from carotid bifurcation
- runs upward through the neck in the carotid sheath
- enters the skull through the carotid canal (located in the petrous portion of the temporal bone)
Describe the course of the vertebral artery as it enters the skull
- arises from subclavian arteries
- posterior to internal carotid
- then proceeds superiorly, in the transverse foramen of each cervical vertebra
What is the functional significance of the circle of willis?
- allows collateral circulation (flow of blood through an alternative route) to take place if flow is reduced to one area / if artery on one side is occluded
- equalises blood slow to different parts of the brain
Each internal carotid artery gives rise to which arteries?
- ophthalmic artery
- posterior communicating artery
- anterior cerebral artery
Which branches are given off from the vertebral arteries?
- meningeal branch
- anterior and posterior spinal arteries
- posterior inferior cerebellar artery
Which arteries do striate arteries arise from?
middle cerebral arteries
Which two sets of veins drain blood from the brain and where do they course?
- superficial veins - run over the surface of the hemispheres and drain into the superior sagittal sinus
- deep veins - converse on the internal cerebral veins which eventually unite to form the great cerebral vein of Galen
where is the superior sagittal sinus located?
lies along the superior edge of the falx cerebri
Explain how blood travels from the superficial veins to the IJV?
Superficial veins –> superior sagittal sinus —> confluence of sinuses —> transverse sinuses —> sigmoid sinus —> IJV
Explain how blood travels from deep veins to the IJV?
Deep veins —> internal cerebral veins —> great vein (of Galen) —> straight sinus —> confluence of sinuses —> transverse sinuses —> sigmoid sinus —> IJV
What are the 3 main types of intracranial haemorrhage?
- extradural
- subdural
- subarachnoid
Which cranial fossa do the temporal lobes lie in?
middle cranial fossa
bleeding from the middle meningeal artery would give rise to which type of intracranial bleed?
epidural
What divides the pre and post central gyrus and what else does this structure mark?
central sulcus
marks the division between the frontal and parietal lobes
What artery is the corpus callosum supplied by?
anterior cerebral artery
what does the coronal suture separate?
frontal from parietal bones
What does the sagittal suture separate?
paired parietal bones
which sulcus separates the temporal lobe from the frontal and parietal lobes?
lateral sulcus
which sulcus separates the left and right hemispheres
great longitudinal sulcus
What attaches the falx cerebri to the skull?
the crista galli of the ethmoid bone
What is the infundibulum/ pituitary stalk?
- between the optic chiasma and the mamillary bodies
- connects to the pituitary gland
What is a fasciculus?
collection of axons in the CNS
What structures do the circle of willis surround?
surrounds the optic chiasma, infundibulum and the interpeduncular region
What is the terminal bifurcation of the basilar artery?
posterior cerebral artery
