- A terminal branch of the
- Neck: lies within the and enters the cranium through the
- Cranium: lies on the roof of the , in close proximity to
- Only has intracranial branches:
- Arise from the
- Definition: a vascular circuit formed by the anastomoses between branches of the internal carotid arteries (anterior circulation) and vertebral arteries (posterior circulation) around the optic chiasm and pituitary stalk
- Consists of paired:
- Two anastomoses
- The circuit provides alternative channels to bypass a potential site of vascular occlusion.
- Equalizes arterial flow to both cerebral hemispheres
Most saccular cerebral aneurysms, also known as berry aneurysms, occur in the anterior circulation of the brain, usually at the junction of the anterior cerebral artery and the anterior communicating artery in the circle of Willis. They are the most common cause of nontraumatic subarachnoid hemorrhage.
|Artery||Arterial territory||Main Branches||Features of stroke|
Branches of the
| || |
Branch of the basilar artery
| || |
- Description: Areas of the brain located at the junction of two nonanastomosing arterial territories, which is most susceptible to ischemia secondary to prolonged hypotension ( ).
- Cortical border zones (external)
- Subcortical border zones (internal): adjacent to the lateral ventricles
Superficial cerebral veins
| Superficial veins |
Drain the white matter
|Draining venous sinus|
Superior cerebral veins
|Superior anastomotic vein||Superiorsagittal sinus|
|Middle cerebral veins||Inferior anastomotic vein||Cavernous sinus|
|Inferior cerebral veins||Cavernous and transverse venous sinuses|
Deep cerebral veins
Deep cerebral veins drain the cerebral medulla and drain into the straight sinus.
- Medullary veins: drain the gray matter
- Subependymal veins: receive blood from the medullary veins
- Basal vein (vein of Rosenthal): paired paramedian veins that receive blood from the temporal lobe and drain into the great cerebral vein
- Great cerebral vein (vein of Galen): receives blood from the deep veins
- The dural venous sinuses drain blood from cerebral veins and CSF from the arachnoid granulations into the internal jugular vein.
- They are located intracranially between the two layers of dura mater (endosteal layer and meningeal layer).
|Superior sagittal sinus|| |
|Inferior sagittal sinus|| |
|Straight sinus|| |
|Occipital sinus|| |
|Confluence of sinuses|| |
Superior petrosal sinus
Inferior petrosal sinus
Basilar venous plexus
Cerebral perfusion is modulated by the partial pressure of carbon dioxide (pCO2)
- Increased pCO2 → vasodilation → increased cerebral blood flow
- Decreased pCO2 → vasoconstriction → decreased cerebral blood flow
- Therapeutic hyperventilation reduces pCO2 → decreases cerebral blood flow → lower intracranial pressure (e.g., used in acute )
- Cerebral perfusion pressure (CPP) = mean arterial pressure (MAP) - intracranial pressure (ICP)