Henry Gray (18251861). Anatomy of the Human Body. 1918.
cerebral, a branch of the basilar. It varies in size, being sometimes small, and occasionally so large that the posterior cerebral may be considered as arising from the internal carotid rather than from the basilar. It is frequently larger on one side than on the other. From its posterior half are given off a number of small branches, the postero-medial ganglionic branches, which, with similar vessels from the posterior cerebral, pierce the posterior perforated substance and supply the medial surface of the thalami and the walls of the third ventricle.
11. The anterior choroidal (a. chorioidea; choroid artery) is a small but constant branch, which arises from the internal carotid, near the posterior communicating artery. Passing backward and lateralward between the temporal lobe and the cerebral peduncle, it enters the inferior horn of the lateral ventricle through the choroidal fissure and ends in the choroid plexus. It is distributed to the hippocampus, fimbria, tela chorioidea of the third ventricle, and choroid plexus.
3b. The Arteries of the Brain
Since the mode of distribution of the vessels of the brain has an important bearing upon a considerable number of the pathological lesions which may occur in this part of the nervous system, it is important to consider a little more in detail the manner in which the vessels are distributed.
The cerebral arteries are derived from the internal carotid and vertebral, which at the base of the brain form a remarkable anastomosis known as the arterial circle of Willis. It is formed in front by the anterior cerebral arteries, branches of the internal carotid, which are connected together by the anterior communicating; behind by the two posterior cerebral arteries, branches of the basilar, which are connected on either side with the internal carotid by the posterior communicating (Figs. 516,519). The parts of the brain included within this arterial circle are the lamina terminalis, the optic chiasma, the infundibulum, the tuber cinereum, the corpora mammillaria, and the posterior perforated substance.
FIG. 519 Diagram of the arterial circulation at the base of the brain. A.L. Antero-lateral. A.M. Antero-medial. P.L. Postero-lateral. P.M. Posteromedial ganglionic branches. (See enlarged image)
The three trunks which together supply each cerebral hemisphere arise from the arterial circle of Willis. From its anterior part proceed the two anterior cerebrals, from its antero-lateral parts the middle cerebrals, and from its posterior part the posterior cerebrals. Each of these principal arteries gives origin to two different systems of secondary vessels. One of these is named the ganglionic system, and the vessels belonging to it supply the thalami and corpora striata; the other is the cortical system, and its vessels ramify in the pia mater and supply the cortex and subjacent brain substance. These two systems do not communicate at any point of their peripheral distribution, but are entirely independent of each other, and there is between the parts supplied by the two systems a borderland of diminished nutritive activity, where, it is said, softening is especially liable to occur in the brains of old people.