Transposition of the great arteries - open duct

Transposition of the great arteries is a congenital (present at birth) heart defect. Because of abnormal development of the fetal heart druing the first 8 weeks of pregnancy, the large vessels that carry blood from hte heart to the lungs, and to the body are improperly connected. Essentially, the connections in the heart are 'swapped'; in transposition of the great arteries, the aorta is connected to the right ventricle and the pulmonary artery is connected to the left ventricle. Because of this, two separate circuits are formed; one that circulates oxygen-poor blood and one that circulates oxygen-righ blood. The presence of other heart defects allows for some mixing of the circulations; An opening in the atrial or ventricular septum will allow oxygen-rich and oxygen-poor blood to mix. Patent ductus arteriosus (the connection between the aorta and the pulmonary artery) such as in this model also allows for some mixing of blood. Because of this, at least some oxygen is provided to the body.