Understanding the Pulmonary Artery

Up from the right ventricle is the pulmonary trunk, a termination point of the pulmonary artery, which branches into the right and left arteries. The right artery comes from a section of the ascending aorta and is the larger of the arterial pair. It passes across the upper chest to the root of the right lung. The shorter left artery passes through the pericardium, the sac around the heart, to the root of the left lung.

The pulmonary trunk comes from two structures. The arterial trunk or truncus arteriosus is the embryonic precursor of what will become the ascending aorta and the pulmonary trunk. Next to this structure is the bulbus cordis, which will become the conus arteriosus or infundibulum. This conical, fibrous base on the right ventricle has an opening from which the pulmonary trunk emerges.

Both arteries split off into lobar and segmental branches. The right lung has three lobes divided into ten segments, while the left lung has eight segments. The right pulmonary artery splits into the truncus anterior and the interlobar artery. The former supplies the upper lobe of the right lung, while the latter supplies the middle and lower lobes. The number of branches from the left artery can vary, but they include the apicoposterior segment in the upper lobe and the lingula and other lower-lobe segments.

To better understand arterial pressure, doctors use PAC or pulmonary artery catheterization. They insert a catheter to check the pressure of the right and left atriums, as well as the pulmonary artery. This procedure can monitor drug therapy and diagnose medical conditions. The pressure of the pulmonary arteries is far lower than systemic blood pressure. Normally, the main artery is between 9 and 20 mmHg at rest, with a slight increase during physical activity.

Blocked or destroyed pulmonary arterioles and capillaries are one cause of pulmonary hypertension. Just as with systemic hypertension, the more the blood flow is impeded, the harder the right ventricle has to work, eventually leading to cardiovascular problems. Symptoms include shortness of breath and cyanosis -- oxygen deprivation that causes a bluish tinge to the skin. Treatments include vasodilators and management of any underlying condition.

Because of the organs involved, pulmonary hypertension is the cause of multiple complications including arrhythmia and blood clots. Cor pulmonale occurs when the heart tries to compensate for the extra energy it takes to push blood through blocked pulmonary arteries. The result is thickened and enlarged right ventricle walls that eventually lead to heart failure. Treatments and prognosis vary depending on the individual medical history and underlying conditions, which include sleep apnea or COPD, chronic obstructive pulmonary disease.

Named after Danish scientist Fritz Valdemar Rasmussen, these aneurysms develop on the wall of the pulmonary artery, close to the superior segments of upper or lower lobes. Due to the location, Rasmussen's aneurysms pose a high risk of rupture and bleeding into the lungs. One common symptom is a bloody cough or hemoptysis. The best treatment option is a coil embolization surgical procedure, which uses a stent at the point of the bulge to resolve the aneurysm.

A pulmonary artery sling occurs when the left pulmonary artery develops between the bronchus and esophagus. This rare, congenital dislocation results in bilateral airway obstruction leading to respiratory distress or cyanosis. Blood supply may be limited to one lung or even a few lobes, causing pulmonary hypertension as well as the collapse of one or both lungs. Symptoms of this condition occur within the first month after birth, and fatalities are likely without surgical intervention.

When a blood clot or other organic material such as collagen or fat blocks the pulmonary artery, this is an embolism. Deep vein thrombosis and clots in the leg veins can cause this event, and consequences range from damage to the lungs from lack of blood to death. Symptoms include chest pain even while at rest, shortness of breath, and bloody coughs. Pulmonary embolisms require aggressive medical attention to improve the patient's chance of survival.

If, during embryonic development, both the left and right ventricles emerge from the truncus arteriosus, the result is a rare congenital heart condition of the same name. This occurs if the fetus has a hole between her ventricles, and it results in the dangerous mixing of oxygenated and deoxygenated blood. Pulmonary hypertension and impeded growth are common symptoms in infants so affected. The first diagnostic sign is a heart murmur, which prompts additional tests such as echocardiograms. The only way to correct the condition is through surgery.