580 ANGIOLOGY 



anterior median artery, which extend as far as the lower part of the medulla spinalis, 

 and is continued as a slender twig on the filum terminale. This vessel is placed 

 in the pia mater along the anterior median fissure; it supplies that membrane, and 

 the substance of the medulla spinalis, and sends off branches at its lower part to 

 be distributed to the cauda equina. 



The Posterior Inferior Cerebellar Artery (a. cerebelli inferior posterior) (Fig. 516), 

 the largest branch of the vertebral, winds backward around the upper part of the 

 medulla oblongata, passing between the origins of the vagus and accessory nerves, 

 over the inferior peduncle to the under surface of the cerebellum, where it divides 

 into two branches. The medial branch is continued backward to the notch between 

 the two hemispheres of the cerebellum; while the lateral supplies the under surface 

 of the cerebellum, as far as its lateral border, where it anastomoses with the anterior 

 inferior cerebellar and the superior cerebellar branches of the basilar artery. 

 Branches from this artery supply the choroid plexus of the fourth ventricle. 



The Medullary Arteries (bulbar arteries) are several minute vessels which spring 

 from the vertebral and its branches and are distributed to the medulla oblongata. 



The Basilar Artery (a. basilaris] (Fig. 516), so named from its position at the 

 base of the skull, is a single trunk formed by the junction of the two vertebral 

 arteries: it extends from the lower to the upper border of the pons, lying in its 

 median groove, under cover of the arachnoid. It ends by dividing into the two 

 posterior cerebral arteries. 



Its branches, on either side, are the following: 



Pontine. Anterior Inferior Cerebellar. 



Internal Auditory. Superior Cerebellar. 



Posterior Cerebral. 



The pontine branches (rami ad pontem; transverse branches') are a number of small 

 vessels which come off at right angles from either side of the basilar artery and 

 supply the pons and adjacent parts of the brain. 



The internal auditory artery (a. auditiva internet; auditory artery}, a long slender 

 branch, arises from near the middle of the artery; it accompanies the acoustic nerve 

 through the internal acoustic meatus, and is distributed to the internal ear. 



The anterior inferior cerebellar artery (a. cerebelli inferior anterior] passes back- 

 ward to be distributed to the anterior part of the under surface of the cerebellum, 

 anastomosing with the posterior inferior cerebellar branch of the vertebral. 



The superior cerebellar artery (a. cerebelli superior) arises near the termination 

 of the basilar. It passes lateralward, immediately below the oculomotor nerve, 

 which separates it from the posterior cerebral artery, winds around the cerebral 

 peduncle, close to the trochlear nerve, and, arriving at the upper surface of the 

 cerebellum, divides into branches which ramify in the pia mater and anastomose 

 with those of the inferior cerebellar arteries. Several branches are given to the 

 pineal body, the anterior medullary velum, and the tela chorioidea of the third 

 ventricle. 



The posterior cerebral artery (a. cerebri posterior) (Figs. 516, 517, 518) is larger 

 than the preceding, from which it is separated near its origin by the oculomotor 

 nerve. Passing lateralward, parallel to the superior cerebellar artery, and receiving 

 the posterior communicating from the internal carotid, it winds around the cerebral 

 peduncle, and reaches the tentorial surface of the occipital lobe of the cerebrum, 

 where it breaks up into branches for the supply of the temporal and occipital lobes. 



The branches of the posterior cerebral artery are divided into two sets, ganglionic 

 and cortical: 



f Posterior-medial. ( Anterior Temporal. 



Ganglionic | Posterior Choroidal. r . , I Posterior Temporal. 

 iPostero-lateral. Calcarine. 



IParietooccipital. 





