Week 3 SDL and Practical Session: Brain, meninges and blood supply

Question 1

Explain the significance of the cephalic flexure in terms of anatomical labels

Answer 1

• 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

Question 2

What does grey matter consist of?

Answer 2

consists of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and unmyelinated axons), synapses and capillaries

Question 3

What does white matter consist of?

Answer 3

• found in deeper tissues of the brain

- contains nerve fibres (axons) covered with myelin, giving its white colour

Question 4

What is the difference between white and grey matter?

Answer 4

grey matter contains numerous cell bodies and few myelinated axons

Question 5

What is the cortex made up of?

Answer 5

• grey matter
• makes up 90% of visible surface of brain
• 10mm thick and folded into sulci (grooves) and gyri (ridges) to increase surface area

Question 6

What is a nucleus?

Answer 6

collection of nerve cell bodies (neurones) within the CNS

Question 7

What is a tract?

Answer 7

• made of white matter

- bundle of axons connecting nuclei of the CNS

Question 8

What is a ganglion?

Answer 8

• 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

Question 9

Which subdivisions of the brain make up the forebrain/ cerebrum?

Answer 9

telencephalon (which contains cerebral hemispheres) and diencephalon (which contains thalamus and hypothalamus)

Question 10

What is the function of the pre-central gyrus and where is it located?

Answer 10

• located in the frontal lobe

- primary motor cortex is responsible for executing voluntary movements

Question 11

What is the function of the post-central gyrus and where is it located?

Answer 11

• located in the parietal lobe

- primary sensory cortex is responsible for receiving sensory information

Question 12

what is the corpus callosum composed of?

Answer 12

white matter - collection of axons that link the neurones

Question 13

What is the function of the corpus callosum?

Answer 13

enables both sides of the brain to communicate and send signals to eachother

Question 14

Which structures are made from the telencephalon?

Answer 14

• cerebral cortex
• hippocampus
• amygdala
• olfactory bulb
• basal ganglia

Question 15

Which structures are made from the diencephalon?

Answer 15

• thalamus
• subthalamus
• hypothalamus
• epithalamus

Question 16

Which structures are made from the mesencephalon?

Answer 16

tectum
cerebral aqueduct
tegmentum
cerebral peduncles
midbrain

Question 17

What structures are made from the metencephalon?

Answer 17

pons and cerebellum

Question 18

What structures are made from the mylencephalon?

Answer 18

medulla

Question 19

What are the 3 meninges that enclose the brain and spinal cord?

Answer 19

• 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

Question 20

What 2 layers is dura mater made up of?

Answer 20

• periosteal outer layer

- meningeal inner layer

Question 21

Where are dural venous sinuses found?

Answer 21

at some sites, the meningeal layer seperates from the periosteum to enclose blood filled spaces into which flows venous blood from the brain

Question 22

What is the name of the dural septum that extends down between the two hemispheres?

Answer 22

falx cerebri

Question 23

What is the name of the dural septum that extends between the occipital lobes of the hemispheres and the cerebellum?

Answer 23

tentorium cerebelli

Question 24

What are the arachnoid villi (also called arachnoid granulations) and what is their function?

Answer 24

• 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

Question 25

Which vessel supplies the dura mater?

Answer 25

middle meningeal artery

Question 26

Describe the course of the internal carotid artery as it enters the skull

Answer 26

- 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)

Question 27

Describe the course of the vertebral artery as it enters the skull

Answer 27

- arises from subclavian arteries - posterior to internal carotid - then proceeds superiorly, in the transverse foramen of each cervical vertebra

Question 28

What is the functional significance of the circle of willis?

Answer 28

- 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

Question 29

Each internal carotid artery gives rise to which arteries?

Answer 29

1. ophthalmic artery 2. posterior communicating artery 3. anterior cerebral artery

Question 30

Which branches are given off from the vertebral arteries?

Answer 30

- meningeal branch - anterior and posterior spinal arteries - posterior inferior cerebellar artery

Question 31

Which arteries do striate arteries arise from?

Answer 31

middle cerebral arteries

Question 32

Which two sets of veins drain blood from the brain and where do they course?

Answer 32

1. superficial veins - run over the surface of the hemispheres and drain into the superior sagittal sinus 2. deep veins - converse on the internal cerebral veins which eventually unite to form the great cerebral vein of Galen

Question 33

where is the superior sagittal sinus located?

Answer 33

lies along the superior edge of the falx cerebri

Question 34

Explain how blood travels from the superficial veins to the IJV?

Answer 34

Superficial veins --> superior sagittal sinus ---> confluence of sinuses ---> transverse sinuses ---> sigmoid sinus ---> IJV

Question 35

Explain how blood travels from deep veins to the IJV?

Answer 35

Deep veins ---> internal cerebral veins ---> great vein (of Galen) ---> straight sinus ---> confluence of sinuses ---> transverse sinuses ---> sigmoid sinus ---> IJV

Question 36

What are the 3 main types of intracranial haemorrhage?

Answer 36

- extradural - subdural - subarachnoid

Question 37

Which cranial fossa do the temporal lobes lie in?

Answer 37

middle cranial fossa

Question 38

bleeding from the middle meningeal artery would give rise to which type of intracranial bleed?

Answer 38

epidural

Question 39

What divides the pre and post central gyrus and what else does this structure mark?

Answer 39

central sulcus | marks the division between the frontal and parietal lobes

Question 40

What artery is the corpus callosum supplied by?

Answer 40

anterior cerebral artery

Question 41

what does the coronal suture separate?

Answer 41

frontal from parietal bones

Question 42

What does the sagittal suture separate?

Answer 42

paired parietal bones

Question 43

which sulcus separates the temporal lobe from the frontal and parietal lobes?

Answer 43

lateral sulcus

Question 44

which sulcus separates the left and right hemispheres

Answer 44

great longitudinal sulcus

Question 45

What attaches the falx cerebri to the skull?

Answer 45

the crista galli of the ethmoid bone

Question 46

What is the infundibulum/ pituitary stalk?

Answer 46

- between the optic chiasma and the mamillary bodies | - connects to the pituitary gland

Question 47

What is a fasciculus?

Answer 47

collection of axons in the CNS

Question 48

What structures do the circle of willis surround?

Answer 48

surrounds the optic chiasma, infundibulum and the interpeduncular region

Question 49

What is the terminal bifurcation of the basilar artery?

Answer 49

posterior cerebral artery