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ANAT242 > Lecture 3- Meninges, Ventricular System and Arterial Blood Supply > Flashcards

Lecture 3- Meninges, Ventricular System and Arterial Blood Supply Flashcards

1
Q

How is the arachnoid mater different to the pia mater?

A

Pia mater adheres tightly to the sulci, arachnoid mater does not (sits above: does not go into grooves)

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2
Q

How is the arachnoid mater connected to the pia mater?

A

By fine strands of connective tissue called arachnoid trabecula

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3
Q

What exits between the arachnoid mater and pia mater? What is found here?

A
  • The Subarachnoid space filled with CSF
  • Contains blood vessels which are prone to bursting/ bleeding blood into the CSF in what is known as subarachnoid haemorrhage
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4
Q

What is concussion due to?

A

Usually CSF in the subarachnoid space provides a watery cushion meaning that when we move our head the brain doesn’t get squished against the hard skull. However, if the head is severely knocked it doesn’t provide enough cushioning and the tissue becomes squished + damaged.

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5
Q

What are arachnoid granulations?

A
  • Arachnoid villi are projections of the arachnoid mater
  • Arachnoid granulations= Aggregations of arachnoid villi which drain CSF into the venous sinuses (veins). In other words they connect the subarachnoid space with a drainage system.
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6
Q

What is a cistern?

A

Enlarged subarachnoid space created where there are major sulci in the brain (Extra space for CSF to pool)

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7
Q

What are the major cisterns? (LABEL THEM)

A
  • Interpeduncular cistern
  • Pontine cistern (smallest)
  • Superior cistern
  • Cerebellomedullary cistern (cisterna magna)
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8
Q

Describe the Pia Mater

A
  • Delicate membrane, follows contours of brain
  • Surrounds blood vessels
  • Sends prolongations into brain tissue along with blood vessels (forming perivascular space)
  • Helps form the roof of the ventricles, closely associated with choroid plexus and ependyma
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9
Q

How are the spinal meninges different to the meninges of the brain? Why is the necessary?

A

For the meninges of the brain there is two layers of dura the periosteal layer and the meningeal layer. For the spinal meninges there is no periosteal layer. This means instead there is an epidural space. The benefit of this is there is an increase in the range of movement for the spinal chord as opposed to the brain (essential!)

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10
Q

Where is the epidural space? Where is it largest? What is contained there?

A
  • Between spinal Dural sheath and vertebral bony wall
  • Largest at L2 (where spinal chord finnishes)
  • Contains fat tissue & venous plexus
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11
Q

What is the idea of an epidural anesthesia?

A

-Inject at L2 into the epidural space. Means there is numbness from this point down. Useful in child birth.

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12
Q

Is there are subarachnoid space in the spinal meninges?

A

Yes, same as brain between the pia mater and arachnoid mater

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13
Q

What is the lumbar cistern and it’s clinical significance?

A
  • Lumbar cistern= inferior to the spinal chord (below L1). A pool of CSF;
  • The clinical significance is that a lumbar puncture can be performed where CSF is drawn from this region. this can be investigated to determine is subarachnoid hemorrhage has occurred and in illnesses such as meningitis
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14
Q

What are the two types of spinal pia mater and what role do they take in anchoring the spinal chord?

A
  • Denticulate ligament (support spinal cord within dural sheath laterally)
  • Filum terminale (conus medularis to the coccyx to anchor in the vertical direction)
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15
Q

What is meningitis? What are the symptoms/ treatment? How is it diagnosed?

A

-characterized by inflammation of the pia/ arachnoid mater
-usually caused by a bacterium or a virus
-common symptoms: fever, headache, vomiting and stiff neck
-diagnosis: performing a lumbar puncture examining
the CSF
-treatment: antibiotics quickly, to prevent infection spreading across pia mater to injure neurons in brain

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16
Q

How many ventricles are there? What are they?

A

4=
• lateral (2)
• third
• fourth

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17
Q

What structures connect the different ventricles? What is the benefit of this?

A
  • Interventricular foramen connects the lateral and third ventricle
  • Cerebral aqueduct connects the third and forth ventricles
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18
Q

What are the lateral apertures?

A

Exit holes from the forth ventricles

19
Q

What are the three horns of the lateral ventricles and where do they sit in terms of the lobes of the brain?

A
  • Anterior horn in the frontal lobe
  • Posterior horn in the occipital lobe
  • Inferior horn in the temporal lobe
20
Q

What parts are there to the lateral ventricles?

A

1 body

3 horns

21
Q

In the lateral horns where is CSF generated?

A

Choroid plexus in the body + inferior horn

22
Q

For the third ventricles where is the choroid plexus (producing CSF) located?

A

-In the roof

23
Q

What exists around/ behind the third ventricle and can be seen in a coronal section?

A

The thalamus

24
Q

Where does the forth ventricle lie?

A

Between the cerebellum, pons and medulla.

After the cerebral aqueduct (leading from the third ventricle)

25
Q

How many openings are there is the forth ventricle? What are these called?

A
  • 2 lateral apertures
  • 1 median aperture

(aperture means hole?)

26
Q

What is the roof of the forth ventricle formed by? What is the floor formed by? Where is the choroid plexus located?

A
  • Superior medullary velum
  • Inferior medullary velum (location of choroid plexus)

-Floor is the brain stem

27
Q

What are three functions of CSF?

A

buoyancy (reduce weight of brain), protection, chemical stability

28
Q

How much CSF is produced per day?

A

500ml

29
Q

What spaces in the brain are filled with CSF?

A

cerebral ventricles, spinal canal, subarachnoid space

30
Q

What is the flow of CSF throughout the brain?

A
  • Lateral ventricles
  • Inter-ventricular foramen
  • Third ventricle
  • Cerebral aqueduct
  • Forth ventricle
  • Goes out lateral apertures or median aperture
  • If goes out median then goes down the central canal of the spinal chord and into the subarachnoid space of spinal chord to circulate back to the subarachnoid space of the skull
  • If goes out the lateral apertures then just goes straight to the subarachnoid space of the skull (more or less)
  • Once in subarachnoid space of skull passes through arachnoid granulations/ villus to drain into sinuses e.g. superior sagittal sinus
30
Q

What is the flow of CSF throughout the brain?

A
  • Lateral ventricles
  • Inter-ventricular foramen
  • Third ventricle
  • Cerebral aqueduct
  • Forth ventricle
  • Goes out lateral apertures or median aperture
  • If goes out median then goes down the central canal of the spinal chord and into the subarachnoid space of spinal chord to circulate back to the subarachnoid space of the skull
  • If goes out the lateral apertures then just goes straight to the subarachnoid space of the skull (more or less)
  • Once in subarachnoid space of skull passes through arachnoid granulations/ villus to drain into sinuses e.g. superior sagittal sinus
31
Q

How is the blood-brain barrier formed and what is it’s purpose?

A
  • Formed by the tight junctions between endothelial cells of cerebral capillaries
  • Selective for nutrients (glucose, amino acids and electrolytes)
  • Acts as a protective mechanism maintaining homeostasis/ stable internal environment for the brain
32
Q

What is the blood brain barrier ineffective against? What is the consequence of this?

A
  • Ineffective against fats, fatty acids, O2, CO2 and fat-soluble molecules including alcohol + nicotine & anaesthetics
  • This is the reason why drugs and alcohol can affect the brain
33
Q

What is hydrocephalus?

A
  • Name means water on the brain
  • Characterized by an excessive amount of CSF in the ventricular system
  • Due to increased production of the fluid, or disturbances in its circulation or in absorption into the venous sinus (blockage)
  • Enlarged head in newborn baby (because the skull bones have not yet fused). Enlarged ventricles creates pressure.

-Gradual ventricular dilation with compression and thinning of brain
tissue in older children and adults. Means mental retardation.

34
Q

How much blood goes to the brain relative to its size? Why is it important to maintain blood flow to the brain?

A
  • Brain constitutes only 2% of body weight, but receives 15% of blood flow (about 750 mL/min)
  • Brain consumes 20% of body’s oxygen and glucose
  • Maintain blood flow is therefore essential and there are systems in place to prevent interruptions (even four mins without blood= irreversible brain damage)
35
Q

What are the two major blood supply routes to the head?

A
  • Common carotid artery is anterior and splits into the internal carotid artery (supplying the brain) and the external carotid artery (supplying the face)
  • The vertebral artery is the other main one running posteriorly
36
Q

What are the three cerebral arteries and what do they branch into?

A
  • Internal carotid: divides into the anterior and middle cerebral arteries
  • Basilar: divides into two posterior cerebral arteries
  • Vertebral
37
Q

What is the circle of Willis? Label a diagram…

A
  • Basilar artery connects to internal carotid artery via posterior communicating arteries, helping to form the Circle of Willis
  • Means blood supply to entire brain is maintained if 1 main artery in Circle is blocked or narrow (goes in other direction of circle)
38
Q

For the circle of Willis what percentage of people have classic anatomy?

A

33%

39
Q

What does the posterior cerebral artery supply?

A

Supply the medial aspect of the hemisphere
(posterior 1/3), occipital lobes, inferior temporal
lobe regions, brainstem, 3rd and lateral ventricles

40
Q

What does the middle cerebral artery supply?

A

Supply almost all of the lateral surface of cerebral hemispheres

41
Q

What does the anterior cerebral artery supply?

A

Supply the medial aspect of cerebral hemispheres (anterior 2/3 only) & basal nuclei

42
Q

What is stroke/ it’s cause?

A

-refers to the neurological dysfunction that results
from a reduction of blood supply to the brain

-due to blockage of a cerebral artery (or vein)
leading to cerebral infarction, or
hemorrhage from an artery (or vein)

-usually caused by an occlusion of a vessel by blood
clot or cholesterol deposit or bleeding from a
ruptured vessel

-The neurological signs and syndromes associated
with a stroke depend on which blood vessels
and their branches are involved.

43
Q

What does occlusion of the anterior, middle and cerebral arteries cause respectively?

A

Anterior cerebral artery
- contralateral hemiplegia (one artery) or bilateral
paralysis (two arteries) & impaired sensation
• greatest in the lower limb

Middle cerebral artery
- a severe contralateral hemiplegia & impaired
sensation
• most marked in the upper limb & face
- severe aphasia (if the dominant hemisphere is affected)

Posterior cerebral artery
- contralateral homonymous hemianopsia (problems with vision)

ANAT242 (25 decks)

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