Pulmonary artery

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.

Structure
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 in length and 3 cm in diameter. It then branches into two pulmonary arteries (left and right), which deliver deoxygenated blood to the corresponding lung.

Function
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. The blood here passes through capillaries adjacent to alveoli and becomes oxygenated as part of the process of respiration.

In contrast to the pulmonary arteries, the bronchial arteries supply nutrition to the lungs themselves.

Pulmonary artery pressure
The pulmonary artery pressure is a measure of the blood pressure found in the pulmonary artery. This is measured by inserting a catheter into the pulmonary artery. The mean pressure is typically 9 - 18 mmHg., and the wedge pressure measured in the left atrium may be 6-12mmHg. The wedge pressure may be elevated in left heart failure and other conditions, such as sickle cell disease.

Clinical significance
The pulmonary artery is relevant in a number of clinical states. Pulmonary hypertension is used to describe an increase in the pressure of the pulmonary artery, and may be defined as a mean pulmonary artery pressure of greater than 25mmHg. This may occur as a result of heart problems such as heart failure, lung or airway disease such as COPD or scleroderma, or thromboembolic disease such as pulmonary embolism or emboli seen in sickle cell anaemia.

Pulmonary embolism refers to an emboli that lodges in the pulmonary circulation. This may arise from a deep venous thrombosis, especially after a period of immobility. A pulmonary embolus is a common cause of death in patients with cancer and stroke. A large pulmonary embolus affecting the pulmonary trunk is called a saddle embolus.

Additional images

 * }