The Human Systemic and Cerebral Circulations: Contrasts in Structure and Function

Abstract

Apart from peculiarities of the cerebral circulation, required to perfuse the brain with the subject erect, the principles established for function of the human systemic circulation (pulsatile flow at input and steady flow at output in capillaries) are identical to those established for other mammals. Assumption of the erect posture first as Homo erectus, then as Homo sapiens, conferred huge advantage to humans and led to command of the mammalian kingdom. But this required a circulation which could perfuse the brain securely against gravity in all positions of the body. This review covers what presently is known about the human cerebral circulation, and how such knowledge can be applied in some clinical conditions including development of dementia in older subjects, and in management of patients with elevation of intra-cranial pressure in younger subjects.