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Anatomy and Neuroscience > Week 6- Cranial Viscera > Flashcards

Week 6- Cranial Viscera Flashcards

1
Q

What 3 layers of membrane surround the brain and spinal cord?

A

Outer- Dura mater
Middle- Arachnoid mater
Inner- Pia mater

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2
Q

What is the main difference between the meninges of the spinal cord and that of the brain?

A

The meninges of the spinal cord contain an outer dural layer between the dura mater and the vertebral column. This forms an epidural space which is filled with fat.

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3
Q

What is the name of the space between the arachnoid and pia mater?

A

The subarachnoid space

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4
Q

What are the two layers of the dura mater and what characterises this difference?

A

Periosteal dura mater: attached to the bone of the skull

Meningeal dura mater: connected to the meningeal layer below (arachnoid mater)

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5
Q

What are extradural (epidural) and subdural spaces and how do they come about?

A

Pathological occurrences that see a space form between the periosteal dura mater and the skull.

Come abut through the haemorrhage of blood vessels

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6
Q

What causes an Epidural hematoma?

A

Rupture of middle meningeal arteries

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7
Q

What causes a subdural hematoma?

A

Venous rupture (slower in nature than that of arteries)

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8
Q

What causes a subarachnoid haemorrhage?

A

The rupturing of major arteries that supply the brain in the subarachnoid space. Usually more serious.

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9
Q

What are dural infoldings?

A

Reflections of the meningeal dura mater away from the periosteal dura mater, forming divisions of the cranial cavity into compartments.

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10
Q

Describe the Falx cerebri dural infolding

A
  • Largest dural infolding

- lies in the longitudinal cerebral fissure

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11
Q

Describe the Falx cerebelli dural folding

A
  • Vertical dural infolding
  • lies inferior to the tentorium cerebelli in post. part of the cranial fossa
  • partially separates cerebellar hemispheres
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12
Q

Describe the Tentorium cerebelli

A
  • Second largest dural infolding
  • separates the occipital lobes from the cerebellum
  • forms tent-like structure with falx cerebri
  • Tent on top of cerebellum
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13
Q

Describe the diaphragma sellae

A
  • Folds over region of sphenoid bone

- covers pituitary gland

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14
Q

Where are dural venous sinuses located?

A

In the edges of some dural foldings

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15
Q

What are the purposes of the dural sinuses?

A
  • Drain CSF

- serve as the venous drainage of the brain, meninges and calvaria

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16
Q

What are dural sinuses lined with?

A

endothelium, roughly triangular in section

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17
Q

What is the largest dural sinus?

A

The superior sagittal sinus

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18
Q

What arteries supply the dura and calvaria?

A

The meningeal arteries, mainly the middle meningeal artery (which is larger than the others)

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19
Q

What do the meningeal arteries do to the skull?

A

Leave impressions on the internal aspect of the skull calvaria

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20
Q

What artery does the MMA branch from?

A

The maxillary artery

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21
Q

What does the MMA enter through?

A

The foramen spinosum

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22
Q

Where does the MMA run?

A

Between the dural layers, sending branches to skull bones

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23
Q

What are ventricles?

A

Fluid filled spaces in the brain, containing specialised capillary structures to produce CSF

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24
Q

What are the different ventricles (4 in total)

A
  • Right lateral
  • Left lateral
  • Third
  • Fourth
25
Q

Describe the flow of CSF through the ventricles

A

CSF flows through ventricles from lateral to 3rd and 4th.

26
Q

What joins the lateral and 3rd ventricles?

A

Interventricular foramen

27
Q

What joins the 3rd and 4th ventricles?

A

Cerebral aquaduct

28
Q

Describe the flow of CSF out of the ventricles

A
  • Leaves ventricles via 1 median aperture and 2 lateral apertures
  • Enters both subarachnoid space and central canal
29
Q

Where are the median and lateral apertures of the ventricles located?

A

Floor of the 4th ventricle

30
Q

Where does CSF originate?

A

Choroid process; capillaries covered by ependymal cells, located;

  • 2 within lateral ventricles (one within each hemisphere)
  • Roof of 3rd ventricle
  • Base of fourth ventricle
31
Q

Describe the process by which CSF is produced

A
  • Produced from blood plasma
  • Substances pass through fenestrated capillaries & though the extracellular space within the pia mater
  • Substances must pass through junctions of ependymal cells via active transport
  • Blood brain barrier is maintained
32
Q

What are the functions of CSF?

A

Mechanical protection:
- Floats brain and softens impact with bony walls
Chemical protection:
- optimal ionic concentrations for action potentials
Circulation
- Waste products to blood

33
Q

Describe the flow of CSF in its reabsorption

A
  • Arachnoid granulations have one way valves
  • Arachnoid villi one-way valves drain CSF into dural sinuses
  • CSF flows from higher pressure in the subarachnoid space to lower pressure in the blood vessel
34
Q

Describe the 2 forms of hydrocephalus

A

NON-COMMUNICATING
- Blockage in ventricular system
- CSF cannot enter subarachnoid space
COMMUNICATING
- CSF enters subarachnoid space but is not reabsorbed into blood
- Common causes: meningitis, thrombus in superior sagittal sinus

35
Q

Describe the water distribution in the CNS

A 
60-68% Intracellular space 
32-40% Extracellular space 
- 12-20% interstitial fluid surrounding cells 
- 10% intracranial fluid =CSF
- 10% intracranial fluid= blood
36
Q

What are glymphatics?

A
  • Unique way of removing interstitial metabolic waste products from the CNS
  • Glial-dependant perivascular network
37
Q

Describe the glymphatics pathway

A
  • CSF enters brain via para-arterial space
  • CSF passes into interstitium via astrocyte pores
  • Fluid flow drive interstitial fluid flow towards para-venous drainage
  • Solutes and waste are cleared from the brain tissue because of this fluid flow and venous drainage
38
Q

What is the blood brain barrier?

A

Barrier created though endothelial cells being anchored to a basal lamina, with structural components limiting the entry of unwanted molecules from the blood into the CNS

39
Q

What are the components of the blood brain barrier?

A
  • Specialised capillary endothelial cells
  • pericytes (contractile cells) forming tight junctions with endothelial cells
  • podocytes (foot processes) and astrocytes enveloping more than 99% of the endothelium
40
Q

What percentage of body weight does the blood supply to the brain make up?

A

2%

  • 15-25% of cardiac output
  • 20% of total body oxygen consumption
41
Q

Describe a peculiarity that is apparent in the brain’s energy supply

A
  • Brain cannot store glucose
  • needs a constant energy supply
  • Can use ketone bodies from lipid oxidation for energy production
42
Q

What structure within the major arterial supply of the brain is also known as the Circle of Willis?

A

Cerebral arterial circle

43
Q

What does the structure of the cerebral arterial circle allow for?

A

Allows for the prevention of decreased performance due to blockages. The alternating pathways allow for accommodation of and changes to flow direction, allowing critical anastomotic flow if a major vessel becomes occluded

44
Q

Describe posterior blood supply to the brain

A
  • Basilar artery gives several cerebellar and pontine arteries–> supply the cerebellum and brainstem
  • Basilar continues rostrally until it bifurcates into posterior cerebral arteries
45
Q

Where is the most common place for aneurysm formation?

A

The basilar artery

46
Q

What does autoregulation of blood flow achieve?

A

Maintains blood flow to brain despite changes in mean arterial blood pressure (MAP)

47
Q

What is the formula for MAP?

A

MAP= DBP + 1/3 PP

*PP= SBP-DBP

48
Q

What is the range of MAP that produces cerebral bloodflow between 45-55ml/100g/min?

A

60-160mmHg

49
Q

What does an increase in MAP lead to?

A

vasoconstriction

50
Q

What does a decrease in MAP lead to?

A

vasodilation

51
Q

What arteries run either side of the medulla to form the basilar artery and where is this located?

A

The left and right vertebral arteries

fuse ventral to the pons

52
Q

Is the subdrual space a real or potential?

A

real

53
Q

What are the 3 main arteries supplying the brain?

A

2 internal carotid arteries and one vertibrobasilar artery

54
Q

How do the internal carotid arteries enter the cranium?

A

Via the carotid foramen, travelling through the carotid canal, penetrating the dura

55
Q

Where do the internal carotid arteries change direction?

A

foramen lacerum

56
Q

What are the (4) main intracranial branches from the internal carotid artery?

A

Anterior cerebral
anterior communicating
middle cerebral
posterior communicating

57
Q

What are the main intracranial branches from the basilar?

A

Cerebellar, pontine and posterior cerebral arteries

58
Q

Where do the vertebral and basilar arteries lie?

A

on the clivus

Anatomy and Neuroscience (9 decks)

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