In human anatomy, the left and right posterior communicating arteries are arteries at the base of the brain that form part of the circle of Willis.
Angiographically, this segment extends from the origin of the posterior communicating artery to the bifurcation of the internal carotid artery.
Sheriff Stuart Forbes returned a formal verdict of death from spontaneous subarachnoid haemorrhage and a ruptured aneurysm of the right posterior communicating artery.
The ophthalmic segment, or C6, extends from the distal dural ring, which is continuous with the falciform ligament, to the origin of the posterior communicating artery.
Blockages of the proximal portion of the vessel produce only minor deficits due to the collateral blood flow from the opposite hemisphere via the posterior communicating artery.
The brain is supplied with blood by the internal carotid arteries and also by the posterior cerebral arteries; the posterior communicating arteries connects the two systems.
The posterior communicating artery is given off as a branch of the internal carotid artery just before it divides into its terminal branches - the anterior and middle cerebral arteries.
The PCA begins as a continuation of the posterior communicating artery in 70-90% of fetuses with the remainder of PCAs having a basilar origin.
The development of the PCA in the fetal brain occurs relatively late and arises from the fusion of several embryonic vessels near the caudal end of the posterior communicating artery.
Oculomotor nerve abnormalities (affected eye looking downward and outward and inability to lift the eyelid on the same side) or palsy (loss of movement) may indicate bleeding from the posterior communicating artery.
In one common variation the proximal part of the posterior cerebral artery is narrow and its ipsilateral posterior communicating artery is large, so the internal carotid artery supplies the posterior cerebrum.
Aneurysms of the posterior communicating artery are the third most common circle of Willis aneurysm (the most common are anterior communicating artery aneurysms) and can lead to oculomotor nerve palsy.
The left and right MCAs rise from trifurcations of the internal carotid arteries and thus are connected to the anterior cerebral arteries and the posterior communicating arteries, which connect to the posterior cerebral arteries.