Development Of CNS, Meninges, CSF and blood supply Flashcards
The nervous system develops from which layer of the embryo?
Ectoderm
Becomes neuroectoderm
What are the stages of embryology of the CNS?
Ectoderm thickens to become the neural plate
Neural plate invaginate to become neural groove, with neural folds at the top. Below neural plate is notochord which secretes chemicals to stimulate development
Neural folds fuse and neural plate becomes neural tube
The PNS is formed from which cells?
Neural crest cells
Which parts of the neural tube form what?
Dorsal - alar plate
Ventral tube - basal plate
What are the meninges?
Membranes of the brain and spinal cord (continuous)
What are the 3 layers of the meninges? Out to in
Dura mater
Arachnoid
Pia mater
What is the function of the meninges?
Provide framework for blood supply
Protection
Flow of CSF
The Dura mater is made of 2 layers in the skull. What are these layers called?
Outer - endosteal
inner - meningeal
Does the dura mater have its own blood supply? What does the dura mater contain?
yes
Venous sinuses
What is the arachnoid? What are the spaces either side of the arachnoid?
Avascular membrane
Space between dura mater and arachnoid - potential space
Space between arachnoid and pia mater - actual space - subarachnoid space
What is the pia mater?
Inner most meninge layer
Highly vascular
Like visceral pleura
What are cuff zones? What is the clinical signifcance of this?
Where meninges join with nerves
Good for anaesthesia
What is the epidural space? What does it contain?
Space between the vertebrae and dura mater
Fat and blood vessels
Where is cerebral spinal fluid?
in the subarachnoid space, ventricles of the brain and central spinal cord
What is the function of CSF?
Shock absorption
Nutrition to nervous tissue
Describe the composition of CSF
No cells or proteins Stable Little AAs and potassium ( prevent firing APs) Low glucose Communicate freely with ISF
the ventricles and central spinal cord are linked by which cells? What is their function?
Ependymal cells (with cilia) Allow transport of CSF
What are the sources of CSF?
Main - choroid plexus (group of ependymal cells in ventricles of the brain)
Minor — ultrafiltrate of pial (surface of brain) blood
What maintains the concentration and osmolarity of CSF? How does it do this?
Blood brain barrier
Ependymal cells pump solutes into CSF, cause water to be drawn out by osmosis
When taking a sample of CSF, where do you take it?
Widening of subarachnoid space
Behind neck
Why is the AA content in CSF low?
Some are neurotransmitters, prevent firing of action potentials
What provides blood supply to the brain?
Cerebroarterial circle
What are the 5 pairs of arteries that supply blood to the cerebroarterial circle?
Rostral cerebral Middle cerebral Dorsal cerebral Rostral cerebellar Internal carotid arteries
Which blood vessels supply the cerebroarterial circle with blood?
Dog/horse - basilar artery
Sheep/cat - maxillary artery
Ox - maxillary and vertebral artery
What are the rete mirabile?
Net of blood vessels to the brain which cool down and reduce the pressure of blood
Which blood vessels supply the spinal cord?
Vertebral arteries and aorta
