The second photo is zoomed in to show the Right and Left Vertibral Arteries. The Right Vertibral Artery originates from the Right Subclavian Artery and supplies blood to the right back part (posterior) part of the brain. The Left Vertibral Artery (LVA) originates from the Left Subclavian Artery and supplies blood to the left posterior part of the brain.

The reason for showing both pictures is to show the blood supply to the brain. The Carotid arteries supply the front part of the brain and the Vertibral arteries supply the posterior part of the brain.

The brain, especially in young people where both arterial systems are open, could compensate for itself. For example, in young children if one of the arteries is blocked the other artery from the opposite side can compensate for it.

If a major one of those arteries is all of a sudden out of blood or if there is a build-up of narrowing (blockage or lipid as what happens in high-cholesterol conditions) and then a clot comes there and closes the remaining pathway, the patient may faint and may even develop a stroke.