Cranial Cavity

Question 1

What are the membranes inside the skull surrounding the brain?

Answer 1

3 meninges:

• Dura mater
• Arachnoid mater
• Pia mater

Question 2

Describe the dura

Answer 2

Outer layer
Tough
Fibrous
Attaches to internal aspect of skull

Question 3

Describe the arachnoid

Answer 3

Intermediate layer
Lines inner surface of dura
More delicate
Still fibrous

Question 4

Describe the pia

Answer 4

Innermost layer
Attached to brain
Very difficult to separate from brain

Question 5

What is the extradural space?

Answer 5

Potential space between skull and dura

Question 6

Where does blood collect when the meningeal arteries rupture?

Answer 6

In extradural space

Question 7

What is the subdural space?

Answer 7

Potential space between dura and arachnoid

Question 8

Where does blood collect with venous bleeding?

Answer 8

In subdural space

Question 9

What is the subarachnoid space?

Answer 9

Real space between arachnoid and pia

Filled with CSF

Question 10

Is there anything between the pia and the brain?

Answer 10

No

Question 11

What are the dural septa?

Answer 11

Dural partitions that project into cranial cavity
Leaves skull
Lodge in between subdivisions of brain
Stop rotational displacement

Question 12

Describe the falx cerebri

Answer 12

Sickle/comma shaped
Lies in midline directly beneath sagittal suture
Partway between two cerebral hemispheres
Free inferior edge
Upper margin attached to skull in midline
Goes posteriorly as far as internal occipital protuberance
Anteriorly plugs into cristagalli of ethmoid bone
In sagittal plane

Question 13

Describe the tentorium cerebelli

Answer 13

Tented
Crescent shaped
In horizontal plane
From posterior aspect of skull
Forms roof for posterior cranial fossa
Lodges between cerebral hemispheres above and cerebellum below
Attached edge posteriorly
Free edge anteriorly

Question 14

Describe the falx cerebelli

Answer 14

Small
Comes in posteroinferiorly
Lodges between cerebellar hemispheres

Question 15

Describe the diaphragma sellae

Answer 15

Roof to sella turcica

Question 16

What is the sella turcica?

Answer 16

Small depression in sphenoid bone where pituitary gland sits

Question 17

Describe the structure of the dura

Answer 17

Like two layers
- Outer = periosteal
- Inner = meningeal
For most part stuck together
Where septa form
- Outer layer continues to line skull
- Inner layer comes down in two places forming double fold

Question 18

What is the dural venous sinus?

Answer 18

Venous pool in little space formed by two layers of dura coming away

Question 19

Describe the dural venous sinus

Answer 19

Endothelial lined space
Between outer an inner layer of dura
Filled with venous blood
Receives blood from
- Brain via cerebral veins
- Spongy bone of skull via diploid veins
- Scalp via emissary veins

Question 20

How can infection from the scalp spread into the brain and meninges?

Answer 20

Venous blood from scalp carrying infection drains into dural venous sinuses

Question 21

Describe the superior sagittal venous sinus

Answer 21

At superior margin of falx cerebri

Gets larger as it extends from anterior to posterior aspect of falx cerebri

Question 22

Describe the inferior sagittal sinus

Answer 22

In inferior aspect of falx cerebri

Between double fold

Question 23

Where does the falx cerebri attach to the tentorium cerebelli?

Answer 23

At inferior margin

Two septa at right angles to each other

Question 24

Describe the straight sinus

Answer 24

Where falx cerebri and tentorium cerebelli join
Here, inferior sagittal sinus straightens out into straight sinus
Runs towards superior sagittal sinus

Question 25

Where do the superior sagittal sinus and the straight sinus meet?

Answer 25

Confluence of sinuses | At internal occipital protuberance

Question 26

Describe the transverse sinuses

Answer 26

Blood goes either left or right at confluence of sinuses Moves in root of tentorium cerebelli Heads all the way around to step between middle and posterior cranial fossae at petrous part of temporal bone

Question 27

Describe the sigmoid sinus

Answer 27

Transverse sinus S-shapes down to jugular foramen and beginning of internal jugular vein

Question 28

Describe the petrosal sinus

Answer 28

Small sinus related to petrous part of temporal bone

Question 29

Describe the cavernous sinus

Answer 29

Either side of body of sphenoid In split in dura over sphenoid Major structures move through them

Question 30

What arteries supply the bones and meninges?

Answer 30

Many small meningeal arteries

Question 31

What is the largest and most important meningeal artery?

Answer 31

Middle meningeal artery

Question 32

What artery is the middle meningeal artery of?

Answer 32

Maxillary artery

Question 33

What foramen does the middle meningeal artery go through to reach the inside of the skull?

Answer 33

Foramen spinosum

Question 34

What are the two branches of the middle meningeal artery?

Answer 34

Anterior | Posterior

Question 35

Which artery grooves the interior aspect of the pterion?

Answer 35

Anterior branch of the middle meningeal artery

Question 36

Where are the meningeal arteries located?

Answer 36

In extradural space | Between dura and skull in little grooves in bone

Question 37

Why is it a medical emergency when a meningeal artery is torn?

Answer 37

``` Thin flat bone of skull fractures > makes sharp spikes > tears artery > blood in extradural space Blood collects Raises ICP Herniation and compression of brain stem Depression of respiratory centres Respiratory arrest ```

Question 38

How do you fix the raised ICP when due to an extradural haematoma?

Answer 38

Drill hole in skull

Question 39

What is the cla suck subdural haemorrhage?

Answer 39

Person falls Tear at point where cerebral veins enter superior sagittal sinus Slow ooze of venous blood into subdural space

Question 40

Is it possible for a subdural haemorrhage to never present?

Answer 40

Yes Sometimes found on autopsy Sometimes calcifies and pits > forms epileptic focus