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.
Surgery for deep venous incompetence. Deep venous incompetence (DVI) is a problem in the veins that can lead to leg ulcers (sores), pain and swelling. It may be caused by a problem in the valves of the vein, by a blockage of the veins or by a combination of these events. For most people, wearing special compression stockings and treating the ulcers is enough. When this does not ease the problem, surgery is sometimes tried.