The left and right posterior communicating arteries are small arteries at the base of the brain, one on each side of the circle of Willis. Each runs back from the internal carotid artery, just before it divides, to the posterior cerebral artery, joining the carotid (front) and vertebral–basilar (back) supplies. [1]
The 3D brain needs JavaScript. The text below still says where the posterior communicating artery is and what it does.
Opens with the blood-supply layer on (about 0.8 MB) and a top (axial) slice through the base of the brain, so the ring is seen from above: the two lit arteries are its sides, running front to back either side of the mammillary bodies. Drag to turn, pinch or scroll to zoom, tap any part to name it; .
Lit: the left and right posterior communicating arteries, the two side links of the circle of Willis; the internal carotids and posterior cerebral arteries they join are not lit (each has its own page). The model draws both the same size. Every other artery shows in a darker colour. [2][1]
In front it joins the internal carotid artery, before the carotid’s split into the anterior and middle cerebral arteries; behind, it joins the posterior cerebral artery. [1]
Each lies in the interpeduncular cistern, above and to the side of the pituitary gland, on the inner surface of the cerebral peduncle on its side and next to the anterior perforated substance. [1]
The oculomotor nerve on the same side passes below and to the outer side of it. [1]
The two often differ in size. Before birth the posterior cerebral artery begins as its continuation; about 20% of adults keep that pattern, so the internal carotid, not the basilar, mainly feeds that posterior cerebral artery. [1]
What it does
It connects the internal carotid supply with the posterior cerebral artery’s, so with the anterior communicating artery it gives the brain’s blood supply alternative routes (collateral circulation). [1]
It contributes to the blood supply of the optic tract, together with the anterior choroidal artery. [1][3]
Small posteromedial central branches leave along its whole length and enter through the posterior perforated substance; one, the anterior thalamoperforating artery, supplies the front of the thalamus. [4]
Other names
Latin: arteria communicans posterior; often shortened to PCoA or PComm. [1]
Size
On this model the left and right posterior communicating arteries fit in a box about 13 mm front to back, 25 mm side to side and 4 mm top to bottom (the box they fit in, not their volume). [2]
Facts describe anatomy and normal function only. The 3D model is the adult male BodyParts3D brain (credits and licence); real brains vary in size and shape, so its measurements describe one model, not anyone’s brain.