Levo-Transposition of the great arteries accompanying defect(s). If a right-to-left or bidirectional shunt is present, the list of symptoms may include mild cyanosis. In a normal heart, oxygen-depleted ("deoxygenated") blood is pumped from the right atrium into the right ventricle, then through the pulmonary artery to the lungs where it is oxygenated. The oxygen-rich ("oxygenated") blood then returns, via the pulmonary veins, to the left atrium from which it is pumped into the left ventricle, then through the aorta to the rest of the body, including the heart muscle itself. With l-TGA, deoxygenated blood is pumped from the right atrium into the morphological left ventricle
Vein directly connect two capillary beds. Examples of such systems include the hepatic portal vein and hypophyseal portal system. The peripheral veins carry blood from the limbs and hands and feet. Microscopically, veins have a thick outer layer made of connective tissue, called the tunica externa or "tunica adventitia". There is a middle layer of bands of smooth muscle called tunica media, which are, in general, much thinner than those of arteries, as veins do not function primarily in a contractile manner and are not subject to the high pressures of systole, as arteries are. The interior is lined with endothelial