Pulmonary Artery Alveolar
The pulmonary artery carries deoxygenated blood from the heart to the lungs. It is one of the only arteries (other than the umbilical arteries in the fetus) that carry deoxygenated blood. In the human heart, the pulmonary trunk (pulmonary artery or main pulmonary artery) begins at the base of the right ventricle. It is short and wide - approximately 5 cm (2 inches) in length and 3 cm (1.2 inches) in diameter. It then branches into two pulmonary arteries (left and right), which deliver de-oxygenated blood to the corresponding lung. The two pulmonary arteries are different in length and anatomy. The right pulmonary artery, the longer of the two, passes transversely across the midline in the upper chest and passes below the aortic arch and enters the hilum of the right lung as part of its root. The left pulmonary artery, the shorter of the two terminal branches of the pulmonary trunk, pierces the pericardium (the sac around the heart) and enters the hilum of the left lung In contrast to the pulmonary arteries, the bronchial arteries supply nutrition to the lungs themselves. Pulmonary hypertension occurs alone and as a consequence of a number of lung diseases. It can also be a consequence of heart disease (Eisenmenger's syndrome) but equally a cause (right-ventricular heart failure); it also occurs as a consequence of pulmonary embolism and scleroderma. It is characterized by reduced exercise tolerance. Severe forms, generally, have a dismal prognosis.