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.
The plaque is so sticky that it keeps the acids in contact with your teeth, in time breaking down the enamel and leading to tooth decay. Plaque buildup can also lead to gum disease -- first gingivitis, the tender and swollen gums that sometimes bleed. If it progresses, severe periodontal (gum) disease can develop. Gum tissue pulls away from the teeth, allowing the bacteria to destroy the underlying bone supporting the teeth.