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BB2 > Anatomy Practical 3 > Flashcards

Anatomy Practical 3 Flashcards

1
Q

What are the 5 layers of the scalp?

A 
S - skin
C - connective tissue
A - aponeurosis
L - loose connective tissue
P - pericranium
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2
Q

What is the skin of the scalp like?

A

Thin, sweat and sebaceous glands, abundant arteries and venous drainage

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3
Q

What is the connective tissue of the scalp like?

A

Thick and richly vascularised

Well supplied with nerves

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4
Q

What is the aponeurosis like?

A

Strong tendinous sheet between muscle bellies of frontalis and occipitalis

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5
Q

What is the loose connective tissue like?

A

Sponge like
Potential to distend with many spaces
Allows free movement of the scalp

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6
Q

What is the pericranium like?

A

Dense connective tissue

Periosteum of the calvaria (skull bones)

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7
Q

Which parts of the scalp are connected?

A

Skin, connective tissue and aponeurosis

Easily separated from pericranium

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8
Q

What are the properties of the dura mater?

A

dense fibrous membrane composed of tough external layer and inner meningeal layer
- dural folds (septa) form as inner layer draws away from outer layer separating brain regions

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9
Q

What is the largest dura septa?

A

Cerebral falx
separates 2 cerebral hemispheres
continuous with cerebellum tentorium in midline

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10
Q

What is the functions of the cerebellum tentorium?

A
  • separates cerebellum and occipital lobe
  • covers posterior fossa structures
  • supports temporal and occipital lobes
  • contains tentorial notch
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11
Q

What is the tentorial notch?

A

gap
brainstem and blood vessels pass to enter middle cranial fossa
tumours can form in this space raise intracranial pressure and can cause uncus herniation

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12
Q

When the brain is removed which meningeal layers get removed with it?

A

Arachnoid and pia mater

Dura remains attached to the inside of the skull

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13
Q

What are the features of the pia mater?

A

Thin

Follows contours of the brain tissue

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14
Q

What are the features of the arachnoid mater?

A

Loosely surrounds the brain
Contains network of CT strands, blood vessels, nerves and CSF
Arachnoid granulations

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15
Q

What are arachnoid granulation?

A

Whitish nodules along fissure

Sites of return of CSF to venous circulation

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16
Q

What are the 2 types of imaging and examples of each?

A

Non-invasive - xray, CT, MRI

invasive - angiography, myelography

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17
Q

How to analyse an x-ray?

A

x-rays use different absorptions

  • provide contrast to the image
  • brain and spinal cord are mostly water so do not absorb enough and are largely invisible
  • bone absorbs a lot so easily seen
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18
Q

How to analyse an MRI?

A
  • uses magnetic properties of hydrogen nuclei
  • sensitive to distinguish CNS tissue
  • sensitive for areas of demyelination, spinal cord lesions, brain lesions
  • use T1 or T2 weighting (refer to measures of energy absorbance and release)
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19
Q

What is seen on T1 weighted MRI images?

A
  • CSF, bone, air and blood emit no signals so rendered black
  • fat and bone marrow have high signal so appear white
  • brain tissue appears intermediate as gray matter
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20
Q

What is seen on T2 weight MRI images?

A
  • reverse of T1
  • CSF, bone, air, blood are white have high signal
  • fat and bone marrow are black and emit no signal
  • brain tissue gray
21
Q

When are T1 and T2 weighting MRI’s used?

A

T1 - to reveal soft tissue damage

T2 - to reveal damage involving fluid containing structures

22
Q

What is the function of gadolinium contrast?

A

Used in MRI’s

does not cross BBB so any lesion disrupting BBB can be seen

23
Q

How to analyse a CT?

A
  • uses xrays to convert differential absorption of them into an electrical signal to then convert to image
  • quick imaging, good resolution and contrast
  • only obtain images in 1 plane at a time so 3D reconstruction of lesions is difficult
  • first line in diagnostic imaging when stroke suspected
  • sensitive to haemorrhagic stroke
24
Q

What are the most usual causes of long term disability after a head injury?

A
  • damage to axons
  • hypoxic-ischaemic damage
    (both sustained at the time of injury)
25
Q

What are the 2 important mechanisms involved in head injury?

A

Impact to the head

Movement of the brain

26
Q

What are focal and diffuse head injuries?

A

focal - indicates pathology that is seen on CT/MRI and may be neurosurgically treatable
diffuse - microscopic damage, diagnosed as unconscious patient’s scan shows little obvious damage

27
Q

What are the different types of skull fractures?

A
  • depressed fracture: area of skull driven inwards, needs neurosurgery repair
  • compound fractures: scalp torn, infection is possible
  • skull base fractures: communication with nasal sinuses, infection possible
  • closed fracture: skin not broken, don’t require treatment usually
28
Q

What are blow-out fractures?

A

Blows around the eye which fracture and displace the orbital walls

  • may involve air sinus damage
  • often produce intraorbital bleeding putting pressure of eyeball and black eyes as accumulates in soft tissue
  • may damage cavernous sinus and its structures
  • infection to cavernous sinuses via ophthalmic vein
29
Q

What happens if the zygomatic bone is fractures in a blow-out fracture?

A
  • double vision as damage to suspensory ligament or obstruction of recti muscles
30
Q

What act as mass lesions?

A

Extradural and subdural haemorrhages
Need to be evacuated neurosurgically
if left untreated can cause death

31
Q

What are the effects of mass lesions inside the skull?

A

differences in pressure between 2 adjacent intracranial compartments causes displacement of the brain into lower pressure compartment (internal herniation)
can also cause ischaemic damage as compression of blood vessels
Cranial nerves also compressed

32
Q

How does an extradural haemorrhage occur?

A

When a blood vessel running between skull and dura is torn
Associated with skull fracture
Either artery or large venous sinus
Mostly middle meningeal artery
Accumulates slowly
Enlarging clot strips dura from skull
Patient may only become unconscious when haemorrhage enlarges to press on the brain
mass effect and raised intracranial pressure can cause death

33
Q

At what volume are haematomas fatal?

A

> 75ml

34
Q

How does a subdural haemorrhage affect?

A
  • by movement of the brain not by impact
  • acceleration with or without deceleration
  • brain movement lags that of the skull
  • traction of bridging veins between brain and dura so get torn
  • blood spreads freely through subdural space
  • damage to axons in underlying brain common
35
Q

What are the key differences between EDH and SDH?

A

EDH - impact caused, underlying brain tissue not severely damaged
IDH - movement caused not impact, damage to axons in underlying brain

36
Q

How does a subarachnoid haemorrhage occur?

A

Almost always insignificant
On surface of hemispheres in relation to fracture sites/contusions
If vessel at base of brain is damaged may collect

37
Q

How is spontaneous subarachnoid haemorrhage different to traumatic subarachnoid haemorrhage?

A

Spontaneous - results from rupture of an aneurysm of vessel of circle of willis, is a form of haemorrhagic stroke

38
Q

Where do contusions occur?

A

On the crests of gyri:

  • inferior surface of frontal lobes
  • lateral and inferior surface of temporal lobes
  • region adjacent to lateral fissures
  • orbital poles
39
Q

What does the term laceration mean?

A

When the arachnoid and brain are damaged

Usually at site of fracture/contusion/large intracerebral haematoma

40
Q

What is diffuse axonal injury?

A

Widespread damage to axons
caused by acceleration with or without deceleration
non-impact like subdural haemorrhage
unconscious patient and remains unconscious, severely disabled until death

41
Q

What are the effects of brain tumours?

A

Mass effect and raised ICP

  • slowly expand
  • presentation may develop over months
  • epileptic seizures
  • abnormal proliferation in glial cells
  • may affect meninges and cerebellum
  • brainstem tumours = poor prognosis
42
Q

What is Alzheimer’s disease?

A

Most common dementia disorder
Progressive, degenerative, disabling
Impaired memory, thinking and behaviour
Rapid death of neurons

43
Q

What forms lesions that arise in dementia?

A

Development of senile plaques and neurofibrillary tangles

2 abnormal proteins - beta-amyloid protein (BAP) and amyloid precursor protein (APP)

44
Q

What are negative signs of basal ganglia abnormalities?

A

When cells no longer elicit activity so actions cannot be performed
- hypokinetic disorders (e.g Parkinsons)

45
Q

What are positive signs of basal ganglia abnormalities?

A

When there is loss of control over cells as disinhibition so actions which patient does not want to perform occur
- hyperkinetic disorders (Huntington’s or hemiballismus)

46
Q

What are the 2 kinds of motor symptoms which occur after cerebellar lesions?

A

1) hypotonia (muscle weakness and loss of motor tone)

2) ataxia (errors in range, rate and force of movement)

47
Q

What are the 3 main cerebellar tumors?

A
  • astrocytoma: in cerebellar hemisphere, surgically removed
  • medulloblastoma: malignant, granular layer of cerebellar cortex, invades 4th ventricle, block CSF flow
  • ependyoma: occur in 4th ventricle, obstruct CSF flow
48
Q

What is MS?

A

Multiple Sclerosis

  • myelin sheath of CNS axons destroyed by immune cells
  • impaired communication between nerve cells
  • abnormal sensations, vision problems, weakness
  • immune T cells activated against myelin components causing local inflammation in brain and cord
  • astrocytes form plaques where myelin once was
  • reduced transmission of nerve signals
  • process to regain myelin not fast enough
  • remyelinated axons thinner with shorter internodes

BB2 (31 decks)

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