The ductus arteriosus is a hole that allows the blood to skip the circulation to the lungs. However, when the baby is born, the blood must receive oxygen in the lungs and this hole is supposed to close. If the ductus arteriosus is still open (or patent) the blood may skip this necessary step of circulation. The open hole is called the patent ductus arteriosus.
Caring for a Bleeding Tooth. Some people mistakenly think that while brushing, a bleeding tooth is perfectly normal. It is not. Anytime there is any bleeding in the mouth, it is almost always a sign of periodontal disease. Even if you brush fairly hard, it should not cause healthy teeth and gums to bleed.
Falling, receiving a blow to the face, or biting down on something hard -- particularly if a tooth already has some decay -- can cause a tooth to chip or break. If you discover you have broken or chipped a tooth, don't panic. There are many things your dentist can do to fix it. How to Care for a Chipped or Broken Tooth