| Pulmonary artery | |
|---|---|
.svg) Anterior (frontal) view of the opened heart. White arrows indicate normal blood flow. (Pulmonary artery labelled at upper right.) | |
| Details | |
| Precursor | Truncus arteriosus |
| System | Cardiovascular,respiratory |
| Source | Right ventricle |
| Identifiers | |
| Latin | arteria pulmonalis |
| MeSH | D011651 |
| TA2 | 4074 |
| FMA | 66326 |
| Anatomical terminology | |
Apulmonary artery is anartery in thepulmonary circulation that carries deoxygenatedblood from the right side of theheart to thelungs. The largest pulmonary artery is themain pulmonary artery orpulmonary trunk from theheart, and the smallest ones are thearterioles, which lead to thecapillaries that surround thepulmonary alveoli.
The pulmonary arteries areblood vessels that carrysystemic venous blood from the right ventricle of the heart to themicrocirculation 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 heart. The main pulmonary arteries emerge from the right side of the heart and then split into smaller arteries that progressively divide and becomearterioles, eventually narrowing into the capillary microcirculation of the lungs where gas exchange occurs.[citation needed]
In order of blood flow, the pulmonary arteries start as thepulmonary trunk that leaves the fibrous pericardium (parietal pericardium) of theventricular outflow tract ofright ventricle (also known asinfundibulum or conus arteriosus.[1] The outflow track runs superiorly and to the left, posterior to thepulmonary valve.[1] The pulmonary trunk bifurcates into right and left pulmonary arteries below thearch of aorta and in front of the left main bronchus.[1] Pulmonary trunk is short and wide – approximately 5 centimetres (2.0 in) in length[2] and 2 centimetres (0.79 in)-3 centimetres (1.2 in) in diameter.[3][4]
The pulmonary trunk splits into theright and theleft main pulmonary artery.[5] The left main pulmonary artery is shorter than the right,[1] passes behind and downwards the descending aorta and above the left main bronchus to the root of the left lung. Above, the left main pulmonary artery is connected to the concavity of the proximaldescending aorta by theligamentum arteriosum.[2] The right pulmonary artery pass across the midline of the body, below thecarina of trachea, and comes in front of the right main bronchus.[1]
The left main pulmonary artery then divides into two lobar arteries, one for each lobe of the left lung.[6]
At the rightroot 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.[1]
The right and left main pulmonary (lungs) arteries give off branches that supplies the correspondinglung lobes. In such cases it is termedlobar arteries.[7] The lobar arteries branch intosegmental arteries (roughly 1 for each segment). Segmental arteries run together with segmental bronchi, at the posterolateral surfaces of the bronchi.[7] These in turn branch intosubsegmental pulmonary arteries.[7] These eventually formintralobular arteries.[8] The pulmonary arteries supply the alveoli of the lungs. In contrast,bronchial arteries, that has different origins, supply the bronchi of the lungs.[1]
The pulmonary arteries originate from thetruncus arteriosus and the sixthpharyngeal arch. The truncus arteriosus is a structure that forms during thedevelopment of the heart as a successor to theconus arteriosus.[9]: 157
By the third week ofdevelopment, theendocardial tubes have developed a swelling in the part closest to the heart. The swelling is known as thebulbus cordis and the upper part of this swelling develops into thetruncus arteriosus.[9]: 159–160 The structure is ultimately mesodermal in origin.[9]: 157 Duringdevelopment of the heart, the heart tissues undergo folding, and the truncus arteriosus is exposed to what will eventually be both the left and right ventricles. As aseptum develops between the two ventricles of the heart, two bulges form on either side of the truncus arteriosus. These progressively enlarge until the trunk splits into theaorta and pulmonary arteries.[9]: 176–179 Failure of these processes can lead topulmonary artery agenesis.
Duringearly development, theductus arteriosus connects the pulmonary trunk and theaortic arch, allowing blood to bypass the lungs.[10]: 791
The pulmonary artery carries deoxygenated blood from theright ventricle to the lungs.[11] The blood here passes throughcapillaries adjacent toalveoli and becomesoxygenated as part of the process ofrespiration.[12]
In contrast to thepulmonary arteries, thebronchial arteries supply nutrition to the lungs themselves.[10]: 790
Thepulmonary artery pressure (PA pressure) is a measure of theblood pressure found in the main pulmonary artery. This is measured by inserting acatheter into the main pulmonary artery.[13]: 190–191 The mean pressure is typically 9–18 mmHg,[14] and thewedge pressure measured in theleft atrium may be 6–12 mmHg. The wedge pressure may be elevated inleft heart failure,[13]: 190–191 mitral valve stenosis, and other conditions, such assickle cell disease.[15]
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.[13]: 720 A pulmonary artery diameter of more than 29 mm (measured on aCT scan) is often used as an indicator for pulmonary hypertension.[16] In chest X-rays, a diameter of more than 16 mm for the right descending pulmonary artery is also an indicator for pulmonary hypertension.[17] This may occur as a result of heart problems such asheart failure, lung or airway disease such asCOPD orscleroderma, or thromboembolic disease such aspulmonary embolism or emboli seen in sickle cell anaemia.[13]: 720–721 Most recently, computational fluid based tools (non-invasive) have been proposed to be at par with the current clinical tests (invasive) of pulmonary hypertension.[18]
Pulmonary embolism refers to an embolus that lodges in the pulmonary circulation. This may arise from adeep venous thrombosis, especially after a period of immobility. A pulmonary embolus is a common cause of death in patients with cancer and stroke.[13]: 720–721 A large pulmonary embolus that becomes lodged in the bifurcation of the pulmonary trunk with extensions into both the left and right main pulmonary arteries is called asaddle embolus.[19]
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.[20]
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