Blood supply of the brain Flashcards
Which 2 arteries are the main supply of the brain?
Vertebral artery and Internal carotid artery
Briefly describe the course of the vertebral artery
The vertebral artery arises from the 1st division of the subclavian artery, ascends up the neck, passing through transverse foramina of the first 6 cervical vertebrae.
It enters the cranial cavity via the foramen magnum and joins with contralateral artery over the medulla, forming the basilar artery
The external carotid supplies the majority of the face and scalp, which structures of the brain does it also supply?
the meninges
The internal carotid artery has no branches in the neck.
Through which foramen does it enter the cranial cavity?
The carotid canal
Where is the circle of Willis located and describe its branches
The circle of Willis surrounds the pituitary stalk.
The basilar artery splits, giving the bilateral posterior cerebral arteries.
Posterior communicating arteries join posterior cerebral arteries to the internal carotid arteries.
Branching from the internal carotid is the anterior cerebral arteries which are joined together by the anterior communicating artery - forming a circle.
The internal carotid artery also branches laterally to give off the middle cerebral arteries.
Which artery supplies the internal capsule?
The lenticulostriate artery (branch of middle cerebral artery)
Which artery supplies the corpus callosum?
The anterior cerebral artery
What is the function of the circle of Willis?
To provide blood flow between anterior and posterior cerebral circulations and to serve as collateral routes in case of obstruction.
What does the anterior cerebral artery supply?
midline regions of the frontal, parietal and cingulate cortices
corpus callosum
What does the middle cerebral artery supply?
lateral side of frontal, temporal and parietal lobes
What does the posterior cerebral artery supply?
occipital lobe
Which arteries supply the lateral ventricles?
The vertebral, basilar and posterior cerebral arteries
Describe symptoms typical of an obstruction in the anterior cerebral artery
Loss of motor innervation of lower limbs
Inability to identify objects properly
Personality changes
(frontal and parietal lobe affected)
Describe the symptoms typical of an obstruction in the middle cerebral artery
Loss of motor innervation of upper limbs (pre and post central gyrus)
Asphasia (if left hemisphere is obstructed- Brocas and Wernickes area)
Describe the symptoms typical of an obstruction in the posterior cerebral artery
Impairment of memory and vision (visual cortex in occipital lobe)
The veins in the brain are valveless and pierce the arachnoid mater and meningeal layer of dura mater.
Describe the drainage of these veins
The veins drain into dural venous sinuses which drain into the sigmoid sinus.
Sigmoid sinus becomes continuous with the internal jugular vein.
There are 7 paired and 5 unpaired sinuses - name these.
paired:
- transverse
- cavernous
- greater and lesser petrosal
- sphenoparietal
- sigmoid
- basilar
unpaired:
- superior and inferior sagittal
- straight
- occipital
- intercavernous
what is the function of the dural septum?
anchors the brain in the cranial cavity
Between which layers of dura do the dural sinuses run?
Dural sinuses run between periosteal and meningeal layers of dura - these layers are not separable in other areas of the brain.
What are the 2 functions of the dural sinuses?
The main function is venous drainage.
The sinuses also resorb CSF (produced in ventricles) via arachnoid villi/ granulations
What is the ‘danger triangle’ ?
The area between the angles of the mouth to the bridge of the nose, infection here can travel via venous drainage to the cavernous sinus.
The cavernous sinus is made up of lots of small channels therefore blood flow is slow, this allows multiplication of bacteria.
This can cause cavernous sinus thrombosis or infection spreading intercranially to meninges.
What are the 3 different types of intercranial haemorrhage?
epidural
subdural
subarachnoid
briefly describe an epidural hematoma
there is no epidural space in the brain (between dura and calvaria) and no space between arachnoid and dura (due to pressure in subarachnoid space) so space here is pathological.
caused by skull fracture at middle meningeal artery
loss of consciousness is quick
Briefly describe a subdural hematoma
associated with old age as tissues become weaker - shock to the brain (eg fall) may cause rupture of vein and bleeding in between dura and arachnoid
slow bleeding as venous
Briefly describe a subarachnoid haemorrhage
referred to as an aneurysm
arterial wall is weaker at junction of arteries, causing aneurysm to burst into subarachnoid space
