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.
Quick Answer. Chronic venous insufficiency is a cause of leaking veins in the leg, reports MedlinePlus. It is a disorder that prevents the veins from adequately sending blood back to the heart after traveling to the legs. Chronic venous insufficiency occurs due to weakened vein walls and damaged valves in the veins, which in return causes the veins to remain full of blood.