The posterior cerebral artery (a. cerebri posterior), a terminal branch of the basilar, lies in the posterior boundary of the arterial circle and is joined to the internal carotid by the posterior communicating artery (Figs. io and 12). It winds backward between the mid-brain and gyrus hippocampi to the tentorial surface of the cerebral hemisphere where, just beyond the splenium of the corpus callosum, it terminates in the calcarine and occipito-parietal branches. From the posterior cerebral arteries originate the postero-median and the postero-lateral ganglionic, and two or more posterior chorioidal arteries and three cortical branches : (1) The temporal branches, often an anterior, middle and posterior temporal, which supply the hippocampal and the fusiform gyri and a part of the lingual and of the inferior temporal gyrus.
(2) The calcarine artery, which runs along the fissure of the same name and supplies the cuneate and lingual gyri; also the pole and the lateral and superior gyri of the occipital lobe. (3) The occipito-parietal artery, a single branch, which runs along the sulcus occipito-parietalis over the supero-medial border to the convex surface of the cerebral hemisphere and is distributed to the cuneus, the prxcuneus and the superior occipital gyrus.
The posterior chorioidal arteries (arterice chorioidece poste riores, Figs. 7, 9 and ro) two or more in number are branches of the posterior cerebral which run forward in the transverse and chorioidal fissures of the cerebrum to the chorioid plexuses of the lateral and third ventricles (Fig. 7).
The anterior chorioidal artery (a. chorioidea anterior) rises from the internal carotid artery just proximal to its anterior and middle cerebral branches, and runs backward and outward along the optic tract to the anterior inferior end of the chorioidal fissure, which it enters (Fig. ro). It terminates in the chorioid plexus of the inferior horn of the lateral ventricle, and gives collateral branches to the optic tract, the gyrus hippocampi, the fascia dentata, the hippocampus, the crus of the fornix and the posterior part of the internal capsule.
A2. The Ganglionic System of .Arteries.—Small arteries
from the arterial circle and from the cerebral arteries near the circle constitute this system (Fig. ro). The arteries pass to their distribution without communicating with one another or with the cortical arteries. They are the end-arteries of Cohn heim. Between the cortical and ganglionic systems, there is an area poorly supplied with blood. That is the area of cerebral softening in old age. The ganglionic system of arteries is made up of six groups of small vessels: The antero-median, the right and left antero-lateral, the postero-median and the right and left postero-lateral.
The antero-median ganglionic arteries rise from the anterior cerebrals in front of the optic chiasma (Fig. so). They supply the chiasma, the lamina terminalis, the rostrum of the corpus callosum, the septum pellucidum and the head of the caudate nucleus.
The antero-lateral ganglionic arteries take their origin, on either side, from the middle cerebral artery, a little outside the arterial circle (Fig. so). They pierce the anterior perforated substance and are distributed to the striated body, internal capsule and thalamus. The largest one of this group is the lenticulo-striate artery. It supplies the greater part of the corpus striatum. On account of its frequent rupture, it is called the artery of cerebral hemorrhage (Charcot).
Postero-median Ganglionic Arteries.—These are branches of the posterior cerebral and posterior communicating arteries (Figs. 9 and so). They supply the interpeduncular structures, the peduncles and, after piercing the posterior perforated sub stance, the walls of the third ventricle and the medial parts of the thalami.
Postero-lateral Ganglionic Arteries.—They rise, on either side, from the posterior cerebral artery after it has wound around the base of the peduncle (Fig. so). They are distributed to the posterior part of the thalamus; the geniculate, quadrigeminal and pineal bodies; the quadrigeminal brachia and the pedunculus cerebri. The superior cerebellar arteries send several branches to the dorsum of the mid-brain, and complete the arterial supply of the cerebrum.