Sharks have skin covered in millions of tiny teeth-like scales that point to the tail. If you rub along a shark towards the tail, it would feel smooth, but if you rub the other way, it would be rough. Sharks' teeth can be 20 times as big as human teeth and they can grow back if they are lost. Fins
Vertebrobasilar insufficiency is a condition characterized by poor blood flow to the posterior (back) portion of the brain, which is fed by two vertebral arteries that join to become the basilar artery. Blockage of these arteries occurs over time through a process called atherosclerosis, or the build-up of plaque.
The vertebrobasilar arterial system perfuses the medulla, cerebellum, pons, midbrain, thalamus, and occipital cortex. Occlusion of large vessels in this system usually leads to major disability or death.Vertebrobasilar stroke carries a mortality rate of more than 85%.roximal to its bifurcation into the terminal branches (PCAs), the basilar artery gives off the superior cerebellar arteries that supply the lateral aspect of the pons and midbrain, as well as the superior surface of the cerebellum.