Pulmonary artery

A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the main pulmonary artery or pulmonary trunk from the heart, and the smallest ones are the arterioles, which lead to the capillaries that surround the pulmonary alveoli.

Structure

The pulmonary arteries are blood vessels that carry systemic venous blood from the right ventricle of the heart to the microcirculation of the lungs. Unlike in other organs where arteries supply oxygenated blood, the blood carried by the pulmonary arteries is deoxygenated, as it is venous blood returning to the lungs. The main pulmonary arteries emerge from the right side of the heart and then split into smaller arteries that progressively divide and become arterioles, eventually narrowing into the capillary microcirculation of the lungs where gas exchange occurs.

Pulmonary trunk

thumb|350px|[[Volume rendering of a high resolution CT scan of the thorax. The anterior thoracic wall, the airways and the pulmonary vessels anterior to the root of the lung have been digitally removed to visualize the different levels of the pulmonary circulation.]]

In order of blood flow, the pulmonary arteries start as the pulmonary trunk that leaves the fibrous pericardium (parietal pericardium) of the ventricular outflow tract of right ventricle (also known as infundibulum or conus arteriosus. Pulmonary trunk is short and wideapproximately in length

The pulmonary trunk splits into the right and the left main pulmonary artery. The left main pulmonary artery is shorter than the right, The right pulmonary artery pass across the midline of the body, below the carina of trachea, and comes in front of the right main bronchus.

At the right root of the lung, it bifurcates into artery that supplies the right upper lobe of the lung, in front of the right upper lobe bronchus, and interlobar artery that supplies the right middle and inferior lobes of the lung, running together with bronchus intermedius. These eventually form intralobular arteries. The pulmonary arteries supply the alveoli of the lungs. In contrast, bronchial arteries, that has different origins, supply the bronchi of the lungs.

By the third week of development, the endocardial tubes have developed a swelling in the part closest to the heart. The swelling is known as the bulbus cordis and the upper part of this swelling develops into the truncus arteriosus.Because the fetus develops within the fluid-filled amniotic sac, hence it relies on the placenta for respiratory gas exchange rather than the lungs.

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. The mean pressure is typically 9–18 mmHg, and the wedge pressure measured in the left atrium may be 6–12 mmHg. The wedge pressure may be elevated in left heart failure,

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 25 mmHg. In chest X-rays, a diameter of more than 16 mm for the right descending pulmonary artery is also an indicator for pulmonary hypertension. 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 embolus 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.

thumb| (made in (1883)) <br> [[Anatomy of the horse, with other arteries: spermatic artery (21), next to (posterior) vena cava, venae portae, External iliac artery, and the mesenteric vessels, Internal iliac and renal arteries labeled. The pulmonary artery and pulmonary veins are labelled (4) and (5), respectively. ]]

Several animal models have been utilized for investigating pulmonary artery related pathologies. Porcine model of pulmonary artery is the most frequently used and it was recently found that their mechanical properties vary with every subsequent branching.

Additional images

File:Relations of the aorta, trachea, esophagus and other heart structures.png|Image showing main pulmonary artery coursing ventrally to the aortic root and trachea, and the right pulmonary artery passes dorsally to the ascending aorta, while the left pulmonary artery passes ventrally to the descending aorta.

File:Illu pulmonary circuit.jpg|Pulmonary circuit

File:Gray503.png|Transverse section of thorax, showing relations of pulmonary artery.

File:Slide16444 (1).jpg|alt=Original image from Anatomist 90|Pulmonary artery

File:Slide44uru.JPG|Pulmonary artery.Deep dissection.Anterior view.

File:Computed tomograph of pulmonary vessels.jpg|CT scan of a normal lung, with different levels of pulmonary arteries.

File:Bronchial anatomy.jpg|Bronchial anatomy

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References

External links

– "Heart: The Pericardial sac and Great vessels"
– "Heart: Openings of Great Vessels into the Pericardial Sac"
– "Mediastinal surface of the right lung"
– "Mediastinal surface of the left lung"