Figure 1 depicts the brain’s blood supply routes. The Carotid arteries – both internal and external branches – serve as the main supply routes. Both originate from the common carotid artery; here we see the right-side supply routes. We have a similar system on the left side too.

Figure 1: Brain’s blood supply routes

Source: openstax.org, RICE University
under the CC BY 4.0 license

The outer external branch transports oxygen and food to the face and all over the skull; the inner branch transports to the inside of the brain.

The junction where the common carotid artery divides into two is a crucial place. It is commonplace where fat deposits, a plaque develops and then narrowing the route happens. We can hear a sound – “bruit” – using a stethoscope. They are at high risk of getting a stroke either by cutting off the blood supply or by dislodging plaque particles. The plaque particles can travel higher through blood further inside and may cut off blood supply to a smaller area of the brain. This type of stroke, which is the commonest type, is called an ischemic stroke.

Figure 2 (below) illustrates the blood supply on the skull base.

Figure 2: Blood supply routes on the base of the brain:

Source: openstax.org, RICE University
under the CC BY 4.0 license

Figure 3 shows the brain regions’ main supply routes: Anterior, middle, and cerebral. Knowing these supply areas is very useful because the impairments due to an interruption to the blood supply in a stroke depend on which supply route is blocked.

Figure 3: Brain’s main blood supply areas according to its supply routes

supply
Source: Frank Gaillard. Patrick J. Lynch, medical illustrator (Brain_stem_normal_human.svg) CC BY-SA 3.0