About 20% of the total blood volume circulates in the brain although it represents 2% of the body weight.
The circle of Willis/circulus Willisi is a circle of arteries that gives rise to all the cerebral arteries. It gets its arterial blood from the two internal carotid arteries/arteria carotis interna and the two vertebral arteries/arteria vertebralis. The carotid artery gives rise to the middle cerebral artery/a.cerebri media on each side and are interconnected via the anterior cerebral arteries/a.cerebri media on both sides and the anterior communicating artery/a.communicans anterior in the front. The internal carotid arteries are also connected to the posterior cerebral artery/a,cerebri posterior from the basilary artery/a.basilaris by the two posterior communicating arteries/a.communicans posterior. The posterior inferior cerebellary artery/a.cerebellaris inferior posterior arises from the vertebral artery whereas the anterior inferior cerebellary artery/a.cerebellaris anterior inferior and the superior cerbellary arteries originate from the basilary artery/a.basilaris. Functionally the anterior cerebral artery and its branches supplies the anterior frontal lobe and the medial portion of the hemispheres. The middle cerebral artery supplies much of the lateral aspects of the hemispheres as well as deep structures in the lateral cerebrum. The posterior cerebral artery curves around the brainstem and supplies the occipital lobe and the lower portion of the temporal lobe.
The venous drainage of the brain includes the dural venous sinuses, the veins of the brain interior, the dural meningeal veins and the diploic veins.