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52 Cards in this Set

  • Front
  • Back
What are meninges?
Protective tissue layers that surround and support the brain and spinal cord
What are three types of meninges?
Pachymeninx (thick)
Leptomeninges (thin)
Spinal meninges
What makes up the Pachymeninx and where is it found?
Dura mater = hard, tightly applied to inner periostium of skull and spinal canal
What makes up the Leptomeninges and where are they found?
1. Arachnoid mater = spider web-like process that extend down to the pia mater

2. Pia mater = single cel layer at the surface of the CNS that 'religiously' follows its contours
Where is the subarachnoid space and what is contained there?
Between arachnoid and pia mater

Contains
1. major blood vessels that branch to enter the CNS
2. CSF
From where do the spinal meninges come?
Continuous with meninges of the brain
What happens to the subarachnoid space in the spinal cord?
Continues down spinal cord, surrounds cord with CSF
Where are the lateral ventricles?
cerebral hemispheres, separated in the midline by the septum pellucidum
Where is the third ventricle?
Single, slit-like midline cavity between thalami
Where is the fourth ventricle?
Floor formed by dorsal pons and medulla, roof by cerebellum
What does the interventricular foramina (of Monro) connect?

How is it formed?
Connects each of the lateral ventricles with the 3rd ventricle

Formed by the arching fibers of the fornix and the thalamus
What does the median aperture of the fourth ventricle (foramen of magendie) connect?
Dorsal 4th ventricle and the subarachnoid space around the base of the cerebellum
What do the lateral apertures (framina of Luschka) connect?
Lateral recess of the fourth ventricle and the subarachnoid space at the lateral junction of the cerebellum and brainstem
What is the Aqueduct of Sylvius?

What does it connect?
A narrow conduit in the dorsal midbrain

connects the 3rd and 4th ventricles
What is the central canal?
continuation of the fourth ventricle in the spinal cord
How does the central canal in kids compare with that in adults?
Children = central canal is a patent tube lined by ependymal cells

Adults = central canal is obliterated, only remnants of ependymal lining is seen
What is the composition of CSF? (5)

How fast is it formed?
Made of water, sodium chloride, protein, gulcose, potassium

500 mL/day
Where is the CSF located?
Fills ventricular system (25 ml)
Fills subarachnoid space (125 ml)
What is the role of CSF in the subarachnoid space? (2)
Shock absorber and spatial buffering in the brain and spinal cord
What is the choroid plexus?

What does it secrete?
Richly vascular secretory apparatus with fenestrated capillaries lined by cuboidal epithelial cells

Secretes CSF
What embryologic structures are related to the choroid plexus?
Ependyma
Where is the choroid plexus present? (5)
1. Lateral ventricle
2. Third ventricle
3. Fourth ventricle
4. Foramina of Monro
5. Extends from fourth ventricle into subarachnoid space through foramina of Luschka
What 2 processes can also generate small amounts of CSF?
1. Metabolic water production
2. Capillary ultrafiltrate
Through what structures is CSF reabsorbed?

How frequent is turnover?
Reabsorbed by arachnoid villi --> venous circulation in superior saggital sinus

3-4 times/day
What makes up the choroid plexus?
Papillae that consist of a simple epithelial layer covering fibrovascular cores
What are tela choroidea?
Attachment points between the epithelium of the choroid plexus and the ependymal lining of the ventricles
What type of cells are choroid plexus epithelial cells
Cuboidal
Some are ciliated
What type of process is CSF secretion?
Active process
What is the function of arachnoid granulations (villi)?
Passive, pressure-dependent, one-way valves between subarachnoid space and the dural venous sinuses
What is a lumbar puncture and why is it done?

What can be measured (4)?
Lumbar puncture at L4-L5 allows for sample of CSF - provides window into subarachnoid space to measure CNS status

1. cells
2. protein
3. glucose
4. Antibody levels or tumor markers in some areas
What is myelography and why is it done?

How is CSF differentiated from brain parenchyma on MRIs?
Introduction of contrast agent into CSF to allow radio graphic visualization of CNS

CSF differentiated by water content
What is hydrocephalus and how does it occur?
Enlargement of the ventricular system from obstruction to flow of CSF
What are 2 common causes of obstructed CSF flow?
1. Congenital block of CSF at the aqueduct of sylvius
2. Impaired reabsorption at the arachnoid villi
What are barriers?
Anatomical and physiological complexes that control movement of substances between ECF of system (bloodstream) and that of the CNS or PNS
What are 2 components of the blood-brain barrier?
1. Tight junctions between adjacent endothelial cells of CNS capillaries, which also lack pinocytotic vesicles

2. Astrocytic foot processes that ensheath CNS capillaries
What are three structural differences between brain and general systemic capillaries?
In brain, capillaries are...
1. joined by tight junctions
2. lack fenestrations and pinocytotic vesicles
3. Surrounded by foot processes of astrocytes
3.
What molecules are permeable across the blood brain barrier? (6)
1. Glucose
2. Amino acids
3. Lactate
4. ribonucleosides
5. lipid-soluble components (ethanol)
6. DOPA
What molecules are impermeable across the blood brain barrier? (4)
1. Albumin
2. Substances bound to proteins (conjugated billirubin)
3. Polar molecules (catecholamines)
4. Some antibiotics (penicillin)
What brain regions have an absent blood brain barrier? (3)
1. Posterior lobe of pituitary gland
2. Pineal gland
3. Circumventricular structures
What are 4 circumventricular structures and what is absent here?
1. Vascular organ of the lamina terminalis - fluid balance, neuroendocrine
2. Subforniceal organ - fluid balance
3. Median eminence of the hypothalamus - continuous w/ infundibular stalk
4. Area postrema - caudal IV ventricle

Lack blood-brain barrier
What are 3 conditions in which the blood-brain barrier might break down?
1. Direct injury of brain capillaries
2. Inflammation
3. Proliferation of new capillaries lacking tight junctions
WHat are the components of the Blood-CSF barrier?
Tight junctions between choroid plexus epithelial cells
How does the surface area of the Blood-CSF barrier compare to that of the blood-brain barrier?
Blood-CSF barrier has 0.2% the SA of the blood-brain barrier
What are typically permeable molecules to the blood-csf barrier? (5)
1. Water
2. Gases
3. Lipid-soluble compounds
4. Micronutrients
5. Small peptides
What are typically impermeable molecules to the blood-csf barrier? (2)
1. Proteins
2. Small polar molecules
What makes up the blood-nerve barrier?
tight junctions between adjacent endothelial cells of endoneurial capillaries in the PNS
What does the blood-nerve barrier prevent?
Entry of large molecules into the endoneurial compartment of peripheral nerves
What is the difference between capillaries of the blood-CSF barrier and those of the blood-brain barrier?
Blood-CSF = fenestrated capillaries

Blood-brain = tight junctions
What substances are actively cleared from the CSF and moved to the blood? (3)
Weak organic acids
Halides
K
What is 1 substance that is actively transported to CSF?
Ascorbic acid
What are 2 substances that go through mediated transport to the CSF?
Glucose
Neutral amino acids
How is CSF secreted?
active secretion