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52 Cards in this Set
- Front
- Back
What are meninges?
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Protective tissue layers that surround and support the brain and spinal cord
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What are three types of meninges?
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Pachymeninx (thick)
Leptomeninges (thin) Spinal meninges |
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What makes up the Pachymeninx and where is it found?
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Dura mater = hard, tightly applied to inner periostium of skull and spinal canal
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What makes up the Leptomeninges and where are they found?
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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 |
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Where is the subarachnoid space and what is contained there?
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Between arachnoid and pia mater
Contains 1. major blood vessels that branch to enter the CNS 2. CSF |
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From where do the spinal meninges come?
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Continuous with meninges of the brain
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What happens to the subarachnoid space in the spinal cord?
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Continues down spinal cord, surrounds cord with CSF
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Where are the lateral ventricles?
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cerebral hemispheres, separated in the midline by the septum pellucidum
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Where is the third ventricle?
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Single, slit-like midline cavity between thalami
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Where is the fourth ventricle?
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Floor formed by dorsal pons and medulla, roof by cerebellum
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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 |
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What does the median aperture of the fourth ventricle (foramen of magendie) connect?
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Dorsal 4th ventricle and the subarachnoid space around the base of the cerebellum
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What do the lateral apertures (framina of Luschka) connect?
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Lateral recess of the fourth ventricle and the subarachnoid space at the lateral junction of the cerebellum and brainstem
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What is the Aqueduct of Sylvius?
What does it connect? |
A narrow conduit in the dorsal midbrain
connects the 3rd and 4th ventricles |
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What is the central canal?
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continuation of the fourth ventricle in the spinal cord
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How does the central canal in kids compare with that in adults?
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Children = central canal is a patent tube lined by ependymal cells
Adults = central canal is obliterated, only remnants of ependymal lining is seen |
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What is the composition of CSF? (5)
How fast is it formed? |
Made of water, sodium chloride, protein, gulcose, potassium
500 mL/day |
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Where is the CSF located?
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Fills ventricular system (25 ml)
Fills subarachnoid space (125 ml) |
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What is the role of CSF in the subarachnoid space? (2)
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Shock absorber and spatial buffering in the brain and spinal cord
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What is the choroid plexus?
What does it secrete? |
Richly vascular secretory apparatus with fenestrated capillaries lined by cuboidal epithelial cells
Secretes CSF |
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What embryologic structures are related to the choroid plexus?
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Ependyma
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Where is the choroid plexus present? (5)
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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 |
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What 2 processes can also generate small amounts of CSF?
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1. Metabolic water production
2. Capillary ultrafiltrate |
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Through what structures is CSF reabsorbed?
How frequent is turnover? |
Reabsorbed by arachnoid villi --> venous circulation in superior saggital sinus
3-4 times/day |
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What makes up the choroid plexus?
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Papillae that consist of a simple epithelial layer covering fibrovascular cores
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What are tela choroidea?
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Attachment points between the epithelium of the choroid plexus and the ependymal lining of the ventricles
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What type of cells are choroid plexus epithelial cells
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Cuboidal
Some are ciliated |
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What type of process is CSF secretion?
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Active process
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What is the function of arachnoid granulations (villi)?
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Passive, pressure-dependent, one-way valves between subarachnoid space and the dural venous sinuses
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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 |
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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 |
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What is hydrocephalus and how does it occur?
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Enlargement of the ventricular system from obstruction to flow of CSF
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What are 2 common causes of obstructed CSF flow?
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1. Congenital block of CSF at the aqueduct of sylvius
2. Impaired reabsorption at the arachnoid villi |
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What are barriers?
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Anatomical and physiological complexes that control movement of substances between ECF of system (bloodstream) and that of the CNS or PNS
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What are 2 components of the blood-brain barrier?
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1. Tight junctions between adjacent endothelial cells of CNS capillaries, which also lack pinocytotic vesicles
2. Astrocytic foot processes that ensheath CNS capillaries |
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What are three structural differences between brain and general systemic capillaries?
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In brain, capillaries are...
1. joined by tight junctions 2. lack fenestrations and pinocytotic vesicles 3. Surrounded by foot processes of astrocytes 3. |
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What molecules are permeable across the blood brain barrier? (6)
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1. Glucose
2. Amino acids 3. Lactate 4. ribonucleosides 5. lipid-soluble components (ethanol) 6. DOPA |
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What molecules are impermeable across the blood brain barrier? (4)
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1. Albumin
2. Substances bound to proteins (conjugated billirubin) 3. Polar molecules (catecholamines) 4. Some antibiotics (penicillin) |
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What brain regions have an absent blood brain barrier? (3)
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1. Posterior lobe of pituitary gland
2. Pineal gland 3. Circumventricular structures |
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What are 4 circumventricular structures and what is absent here?
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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 |
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What are 3 conditions in which the blood-brain barrier might break down?
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1. Direct injury of brain capillaries
2. Inflammation 3. Proliferation of new capillaries lacking tight junctions |
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WHat are the components of the Blood-CSF barrier?
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Tight junctions between choroid plexus epithelial cells
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How does the surface area of the Blood-CSF barrier compare to that of the blood-brain barrier?
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Blood-CSF barrier has 0.2% the SA of the blood-brain barrier
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What are typically permeable molecules to the blood-csf barrier? (5)
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1. Water
2. Gases 3. Lipid-soluble compounds 4. Micronutrients 5. Small peptides |
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What are typically impermeable molecules to the blood-csf barrier? (2)
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1. Proteins
2. Small polar molecules |
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What makes up the blood-nerve barrier?
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tight junctions between adjacent endothelial cells of endoneurial capillaries in the PNS
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What does the blood-nerve barrier prevent?
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Entry of large molecules into the endoneurial compartment of peripheral nerves
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What is the difference between capillaries of the blood-CSF barrier and those of the blood-brain barrier?
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Blood-CSF = fenestrated capillaries
Blood-brain = tight junctions |
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What substances are actively cleared from the CSF and moved to the blood? (3)
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Weak organic acids
Halides K |
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What is 1 substance that is actively transported to CSF?
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Ascorbic acid
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What are 2 substances that go through mediated transport to the CSF?
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Glucose
Neutral amino acids |
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How is CSF secreted?
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active secretion
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