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.
An uncorrected PDA may lead to congestive heart failure with increasing age. The ductus arteriosus is a fetal blood vessel that closes soon after birth. In a PDA, the vessel does not close and remains patent (open), resulting in irregular transmission of blood between the aorta and the pulmonary artery.rom Wikipedia, the free encyclopedia. Patent ductus arteriosus (PDA) is a congenital heart defect wherein the ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain.