3 Flashcards
(60 cards)
1
Q
What are the three membranous layers that surround and protect the brain and the spinal cord?
A
- Pia mater
- Arachnoid mater
- Dura mater
2
Q
What do the pia and arachnoid mater make up?
A
The leptomeninges
3
Q
Describe the dura mater
A
- dura mater= tough mother
- really dense CT that doesn’t dip into any of the folds of the brain
- directly under the skull
4
Q
Describe the space between the dura and arachnoid mater
A
- known as the sub-dural space
- is only a POTENTIAL SPACE
- arachnoid mater is pushed up against the dura mater due to pressure of CSF, thus it is only a potential space
5
Q
Describe the arachnoid mater
A
- Runs smoothly over most folds
- dips into the fissures
- consists of a soft translucent membrane
6
Q
Describe the subarachnoid space
A
- contains CSF and cerebral vessels that supply/drain the brain
- space between the arachnoid and dura mater
7
Q
Describe the pia mater
A
- area adjacent to brain
- microscopically thin, delicate adherent to surface of brain, follows every fold
- kind of like visceral pleura, since it follows every fold
8
Q
What is the large dip between the two hemispheres of the brain known as?
A
Longitudinal fissure
9
Q
What part of the ethmoid bone does the longitudinal fissure attach to?
A
Crista galli (on inferior side of skull)
10
Q
Explain how dura is like a “two-ply” tissue
A
-dura for the most part consists of two layers which are closely adhered and appear as a single layer
2 layers:
-periosteal: part against the inner table of bone (immediately facing skull)
-meningeal: part adjacent to arachnoid (immediately facing the brain)
-sometimes the layers separate and they form: dural folds, dural venous sinuses (spaces which are filled with venous blood= venous channels)
11
Q
Explain what the cavernous sinus is
A
- formed the same as DVS but occurs on the cranial floor while dural is in cranial vault
- cavernous sinus has lots of mini cavities within it made of fibrous tissue
- has lots of structures travelling through it
- sits on either side of the sella turcica in the middle cranial fossa
- drains into other DVS and eventually leaves through IJV
12
Q
Explain the relationship between dural folds and DVS
A
- dural folds do not occur for EVERY DVS
- formation of DVS will create a dural fold
- meningeal dura tears away to create a gap for the venous sinus, and then meet again to make the dural fold
13
Q
What is the vertical dural fold called and what does it attach to?
A
- falx cerebri
- attaches to crista galli in the anterior cranial fossa
- attaches to the horizontal dural fold (tentorium cerebelli) in the posterior bit
14
Q
What is the horizontal dural fold called? What is its function?
A
- tentorium cerebelli
- forms like a tent over the posterior cranial fossa
- extension of the dura mater that separates the cerebellum from the inferior portion of the occipital lobes
15
Q
Explain the function of dural folds
A
- helps to stabilize the brain and act as rigid dividers
- BuT a rise in pressure inside the skull (i.ee secondary to bleeding) can lead to herniation of parts of the brain under rigid dural folds and/or through foramen magnum
- because of the rigid folds, the brain can actually herniate into other areas
16
Q
Explain what dural venous sinuses are
A
- venous blood filled spaces created by separation of meningeal from periosteal layer of dura
- found throughout the skull, surrounding the brain within the areas where two layers of dura separate to create a “space”
- DVS connected to each other and receive blood from cerebral veins (draining brain)
- eventually DVS drain into IJV
17
Q
What sinuses form the top and base of the falx cerebri?
A
- superior sagittal sinus (top)
- inferior sagittal sinus (base)
18
Q
How is straight sinus created and what does it connect?
A
- created at the area where the falx cerebri meets the tentorium cerebelli
- connects the the superior and inferior sagittal sinuses
19
Q
What is the confluence of sinuses?
A
- found at the back of skull
- where a lot of the sinuses are connected together
- common intersection for many sinuses
20
Q
What comes off laterally of the confluence of sinuses?
A
Transverse sinus
-goes laterally around the skull on both sides of the confluence
21
Q
Where does the sigmoid sinus arise from
A
- comes from the transverse sinus
- makes an S-shaped bend
- eventually becomes IJV
22
Q
What are the superior and inferior petrosal sinuses?
A
- run close to the petrous bone (superior and inferior ridge of petrous bone)
- connects the cavernous sinus to other sinuses
23
Q
How can I learn more about the sinuses?
A
LOOK AT THE DIAGRAMS
24
Q
What are bridging veins?
A
- they traverse the sub dural “space”
- connect cerebral veins to DVS
- Bridging to Brain
25
What are emissary veins
- traverse through the skull
- connect between the extracranial veins and its DVS
- pass through the skull bone and connect veins outside of the skull to veins inside the skull
26
What is an intracranial haemorrhage?
- head trauma that leads to bleeding in “spaces” between the meningeal layers
- blood vessels run along or traverse between the meningeal layers
- addition of “volume” to an already fixed space (skull) leads to rise in pressure and damage to brain tissue, brain stem and other important structures (ex. Cranial nerves)
27
What is the difference between intracranial and intracerebral haemorrhages?
- Intracerebral: happens within the brain tissue itself (eg. Contusions, tearing of white matter)
- Intracranial: out of brain tissue but somewhere in the meninges
28
What are the different types of intracranial haemorrhages?
Extradural, subdural, subarachnoid
29
Describe an extradural haemorrhage
- between inner table of bone and the periosteal dura
- bleeding will start to strip the periosteal layer of dura, but sutures will halt bleeding
- can occur during a punch to the pterion
- will cause significant increase in pressure, so need to surgically evacuate the blood
- haemorrhage will appear bright white on a CT scan and LENS-SHAPED
- pt. Will experience headache
- usually arterial blood
30
Describe a subdural haemorrhage
- usually venous blood from bridging veins
- weakest point: where bridging veins join the wall of the dura
- as you age, cerebral atrophy occurs so there will be increased tension and stretching on the bridging veins as it joins DVS
- if an oldie bumps their head, they can potentially pull the bridging vein away from its connection to DVS so blood will start to fill the potential space
- haemorrhage appears banana-shaped on a CT scan
- pt. Will experience a headache
31
Describe a subarachnoid haemorrhage
- usually arterial blood
- secondary to trauma or spontaneous rupture of blood vessel (ex. Aneurysm that will pop)
- usually from a branch of “circle of Willis” (arterial circuit that supplies brain structures)
- blood leaks into subarachnoid space, mixing with CSF
- sudden and is often fatal
- blood is very irritant to surface of brain
- pt. Will usually experience symptoms similar to meningitis (i.e. headache, photophobia) since meninges are irritate
- CT: 93% picked up if within 24 hours; 100% if within 6 hours
- if CT is inconclusive then a lumbar puncture is done (sample CSF to identify presence of blood)
32
Which bones form the pterion?
-temporal, frontal, parietal, and sphenoid
33
What bones does the anterior cranial fossa consist of?
Frontal, ethmoid, and sphenoid
34
What are the boundaries of the anterior cranial fossa?
- anteriorly and laterally: inner surface of frontal bone
- posteriorly and medially: limbus of sphenoid bone
- posteriorly and laterally: lesser wings of sphenoid bone
- floor: frontal, ethmoid and sphenoid
35
What bones does the middle cranial fossa consist of?
-sphenoid and the two temporal bones
36
What are the boundaries of the middle cranial fossa?
- anteriorly and laterally: lesser wings of sphenoid bone
- anteriorly and medially: limbus of sphenoid bone
- posteriorly and laterally: superior border of the petrous part of temporal bone
- posteriorly and medially: dorsum sellae of sphenoid bone
- floor: body and greater wing of sphenoid and squamous and petrous part of temporal bone
37
What bones does the posterior cranial fossa consist of?
-occipital bone and two temporal bones
38
What are the boundaries of the posterior cranial fossa?
- anteriorly and medially: dorsum sellae of sphenoid bone
- anteriorly and laterally: superior border of petrous part of temporal bone
- posteriorly: internal surface of squamous part of occipital bone
- floor : mastoid part of temporal bone and squamous, condylar and basilar parts of occipital bone
39
What ‘cavities’ lies immediately beneath the anterior cranial fossa?
-nasal, orbital, superior and inferior optic fissures
40
What are the foramina and fissures of the middle cranial fossa?
```
ROLS
foramen Rotundum
-foramen Ovale
-foramen Lacerum
-foramen Spinosum
```
41
What name is given to the ‘spaces’ with which foramen rotundum and foramen ovale communicate? The maxillary and mandibular division of the trigeminal nerve pass through each of these foramina respectively.
Pterygopalatine fossa: maxillary, foramen rotundum
| Infratemporal fossa: mandibular, foramen ovale
42
Which bones contribute to the zygomatic arch?
-zygoma, temporal and sphenoid
43
What nerve exits through the maxilla and infra-orbital foramen?
-infra-orbital nerve
44
What bone forms the hard palate?
-palatine process of maxilla
45
What are the three extracranial fossae?
Temporal, infra-temporal, pterygopalatine
46
What does the CNS develop from?
A tube of ectoderm
47
What is emergence?
-phenomenon where complex behaviour “emerges” from the interaction of individual, relatively simple units
48
What are the components of the CNS?
- cerebral hemispheres
- brainstem and cerebellum
- spinal cord
- incapable of regeneration
49
What are the components of PNS?
- dorsal and ventral roots
- spinal nerves
- peripheral nerves
- capable of regeneration
50
Why are the superior and inferior parts of the brain dorsal and ventral respectively?
- brain flexes at 90 degrees around the level of midbrain
- so superior part of hemisphere is dorsal while inferior part is ventral
- thus dorsal/ventral brain structures are not necessarily closes to the back/belly respectively
51
Describe the midbrain
- top of brain stem
- eye movements and reflex respose to sound and vision
- ex: see/hear the danger such as lion, but wont recognize that it is a lion as opposed to tiger
52
Describe the pons
- middle bit of brainstem, bulges out
- feeding and sleep function
- trigeminal nerve emerges from pons
- pons=bridge
- has transverse bridging fibres to connect the cerebellum
- ex: newborn feeding and sleeping
53
Describe the medulla
- cardiovascular and respiratory centres
- contains a major motor pathway (medullary pyramids, which ultimately decussate)
- bottom of stem
- decussation= cross over
- body is controlled by contralateral side of brain
54
Describe sulci
- a “groove or furrow” in the brain separating adjacent gyri
| - central sulcus separate the anterior and posterior parts of brain
55
What functions are the anterior and posterior parts of brain responsible for?
```
Anterior= motor (move forward)
Posterior= sensory
```
56
Describe gyri
-a “ridge or fold” in the brain
57
Describe a fissure
-large “crack” or “split” between adjacent large areas of the brain
58
What lobes can one see in the lateral aspect of the cerebral hemisphere? Describe them
Frontal lobe: higher cognition, motor function, speech, behavioural control
Parietal lobe: sensation, spatial awareness
Temporal lobe: memory, smell, hearing, emotional processing
Occipital lobe: vision, visual centres at back since front lobes have expanded so much
Cerebellum: coordination and motor learning
SEE DIAGRAM
59
Describe the structures at the inferior aspect of the cerebral hemisphere
- optic chiasm: site where fibres in the visual system cross over
- uncus: part of temporal lobe that can herniate, compressing the brain
- medullary pyramid: location of descending motor fibres
- each nerve contains around a million axons
60
Describe the structures on the medial aspect of the cerebral hemisphere
- corpus callosum: fibres connecting the two cerebral hemispheres (white matter, axons)
- thalamus: sensory relay station projecting to sensory cortex (must go through thalamus to be consciously perceived)
- hypothalamus: essential centre for homeostasis
