What Is a Cerebellar Artery?

The cerebral arteries have a pair of internal carotid arteries and vertebral arteries connected to each other to form an arterial circulation. The venous system is not mixed with the arteries of the same name. The collected venous blood first enters the sinus and then flows into the internal jugular vein. There is no valve at all levels . It includes the arterial system of the brain and the venous system of the brain.

Cerebral artery

Cerebral arteries have pairs

The supply of cerebral blood flow comes from two arterial systems:

Each side

(One)

(A) Willi's ring. Although the internal carotid artery system and the vertebrobasilar system are two independent blood supply systems, there are also extensive collateral circulations. The most important one is the Willi's ring. ring). The anterior cerebral arteries on both sides are connected to each other by a short anterior communicating artery; the internal carotid artery and posterior cerebral artery on both sides are connected by a posterior communicating artery to form a cerebral arterial ring. Under normal circumstances, the direction of blood flow in the arteries that make up the ring is fixed, and they do not mix with each other. Only when the blood flow is blocked at the proximal end of an artery and the pressure difference between the arteries in the ring, the cerebral arterial ring can play its side branch Cyclic effect. Therefore, to understand what symptoms may occur in a single cerebral artery occlusion, it is necessary to understand the condition of the cerebral arterial ring. A variety of congenital mutations can occur in the cerebral arterial ring, which may prevent the collateral circulation from functioning quickly and effectively. This is one of the important factors affecting the occurrence of cerebral infarction. According to statistics, only 50% of the complete ring. It has been reported that in patients with non-cerebral infarction disease, the normal circle is 52%, while only 33% of patients with cerebral infarction. Others have reported that the abnormality rate of this ring reaches 79%. The most abnormal of this ring is the small posterior communication artery from the internal carotid artery and the posterior cerebral artery separated from the internal carotid artery. In an unselected group of autopsies, 32% of posterior communicating arteries were less than 1 mm in diameter; 30% of the posterior cerebral arteries originated from the internal carotid artery. Other common abnormalities include anterior communicating artery dysplasia , Accounting for 29%, and the anterior communicating artery increased to two branches, accounting for 33%. The anterior cerebral artery between the internal carotid artery and the anterior communicating artery is only 13%. In a group of patients with cerebral infarction, 38% of posterior communicating artery diameters were less than 1 mm in diameter, compared with 22% without infarction, and 29% of posterior cerebral arteries originated from internal carotid artery, compared with 15% of normal. In another group of reports, 59% of patients with small posterior cerebral infarction had more than 15% of those with non-cerebral infarction (39%), and those with no posterior or bilateral posterior communicating artery or only residual remains, up to 15%; The anterior cerebral artery fused into a single branch or divided into 3 branches to 12%; 15% of the posterior cerebral arteries came from the anterior circulation internal carotid artery system, not from the posterior circulation.

(B) Other collateral circulations In addition to the cerebral arterial ring, there are also cerebral arterial anastomosis in other parts, which can play the role of collateral circulation.

(1) On the surface of the brain, the anterior, middle, and posterior cerebral cortex branches communicate with each other, as dense as a spider web;

(2) The deep and shallow branches of the internal and external carotid arteries surrounding the eyes, ears, and nose coincide with each other;

(3) There is also a rich anastomosis of the cerebral cortex and the meningeal artery (external carotid artery branch), which can play an important role when the internal carotid artery is narrowed or occluded.

(4) The mesial branch is often considered to be a terminal artery. In fact, there are also abundant vascular anastomosis between adjacent central branches, but the anastomotic branch is small and cannot complete an effective collateral circulation. The anterior and posterior circulation watersheds are located at the junction of the parietal, temporal, and occipital regions in the cortex, and at the thalamus level in the deep. The effectiveness of collateral circulation is also determined by the occlusion of the main vessel.