Brain Circulation, Meninges, and CSF Flashcards
1
Q
Carotid Artery and Internal/external
A
- Main ones shown to supply the whole head are the two common carotid arteries (left and right)
- main supply to the whole head region
- derives from aortic arch
- -common carotid artery ends by forming into 2: an internal carotid artery and an external carotid artery
- beyond this, the external carotid artery goes to form many branches to supply much of the head structures, the main exception being the brain
- the brain is supplied by the internal carotid artery. Doesn’t give off branches until it reaches its termination and supplies the brain
- due to this formation, we have a trunk root of blood supply to the brain
- From the heart (or the aortic arch) through the common carotid arteries and internal carotids which don’t have significant branches along the way–> all the blood in these vessels need to supply the brain!
2
Q
Cerebral Arterial Circle
(Loop of Willis)
A
- Can see an obvious circular arrangement of arteries lying on the ventral surface of the diencephalon which is called the Cerebral Arterial Circle
- circle of arteries supplying the brain
- many branches in a circle going to supply various regions in the brain
- named quite specifically by location
- MUCH of the brain is supplied by this arterial circle
- The Cerebral arterial circle is being supplied by the internal carotid artery on either side of the brain and the Basilar Artery!
3
Q
Basilar Artery
A
- Midline artery running over the ventral aspect of the brain stem and reaching caudal end of the arterial circle –> Basilar Artery
- Also contributes blood supply to the arterial circle
- the Basilar artery also gives rise to some branches supplying the Caudal Cerebellar region and other parts of the hindbrain
- supplies a relatively small amount of the brain compared to branches coming off the arterial circle
- there are two vertebral arteries that fuse to form the basilar artery
4
Q
Supply TO the arterial circle
A
- Internal carotid a. (2)
- Basilar a. (formed by union of 2 vertebral aa.)-terminally unite to form the single basilar artery
- This is the arrangement in many mammals including primates, horse, dog and pig
- Not the case in ALL mammals
5
Q
Vertebral Artery
A
Vertebral a.
- Branch of subclavian a. in thorax
- Runs through transverse foramina in cervical vertebrae
- Then enters cranial cavity via foramen magnum
- In the cranial cavity, the vertebral arteries unite to form the midline vessel, the basilar a.
6
Q
Variation of Cerebral Arterial Circle
A
In some other species including CATS and RUMINANTS:
- The internal carotid develops, but regresses postnatally and conveys NO BLOOD to the brain
- SO, other channels to arterial circle must exist
7
Q
Venous Drainage of the Brain
A
- Cerebral veins lack valves: there is potential for venous blood ot flow in either direction
- Drain to venous sinuses of dura mater (which are venous channels, but not veins due to differing structure)
8
Q
3 layers of the Meninges (and spaces between)
A
- Dura mater (outer)- then subdural space
- Arachnoid (middle)-then subarachnoid space
- Pia mater (inner)
9
Q
Epidural Space
A
- Lies between periosteum and dura in vertebral canal (NOT CRANIAL CAVITY)
- COntains- loose connective tissue, veins and lymphatics
- Cushions the cord as it flexes (as vertebral column flexes)
- Can be used for nerve blocks (epidural anasthesia)
- NOTE: Cranial periosteum and dura mater are fused- in effect one single layer, no space
10
Q
Fax Cerebri
A
- A fold (projection) of dura mater that leaves the periosteum of the skull and projects into the brain between the two cerebral hemispheres
11
Q
Dura Mater
A
- Dense connective tissue
- fused with the periosteum of the cranium
- contains the venous sinuses
12
Q
Subdural Space
A
- Lies between dura mater and arachnoid
- Potential space containing only lymph-like fluid
- Site of subdural haematomata
13
Q
Arteries to Brain
A
Brain= largest mass of nervous tissue in the body
- Needs rich blood supply (due to requirements of nervous tissue)
- Must be maintained throughout life
14
Q
Common carotid a.
A
= main supply to head (from the aortic arch)
- Internal carotid a. (unbranched) – main supply to brain (direct)
- External carotid a. (many branches) – supply head other than brain
15
Q
Cerebral Arterial Circle
A
Circle of arteries lying on the ventral surface of the brain, circling around the diencephalon
- Supply TO circle- The paired internal carotid arteries
- Basilar artery (formed by union of paired vertebral* aa.)-feeds into caudal extremity of the CAC
- This is arrangement in many mammals including primates, horse, dog and pig
*Vertebral artery- Branch of subclavian a. (main arterial trunk in forelimb), runs through transverse foramina in cervical vertebrae cranial cavity via foramen magnum–> unite to form basilar a.
27
Q
Arachnoid Granulations
A
- Arachnoid granulations, also known as a Pacchionian granulation, are projections of the arachnoid membrane (villi) into the dural sinuses that allow CSF entrance from the subarachnoid space into the venous system
28
Q
Cisterns of the Subarachnoid space
A
- subarachnoid cisterns are discrete named spaces within the subarachnoid space where the pia mater andarachnoid membrane are not in close approximation.
- The subarachnoid tissue is not as abundant here as in the normal subarachnoid space and cerebrospinal fluid (CSF) gathers to form pools or cisterns
- Lumbar Cistern - dangerous as in our domstic animals, the spinal cord runs through the lumbosacral junction! Risk damage to the spinal cord. Doesn’t provide an easy route to get needle to lumbar system. Terminates much earlier in man!
- Cerebellomedullary cistern: around foramen magnum, used for collection of CSF
