A pulmonary artery is an

artery An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pul ...

in the

pulmonary circulation The pulmonary circulation is a division of the circulatory system in all vertebrates. The circuit begins with deoxygenated blood returned from the body to the right atrium of the heart where it is pumped out from the right ventricle to the lungs ...

that carries deoxygenated

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...

from the right side of the

heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...

to the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

s. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the

, and the smallest ones are the

arteriole An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries. Arterioles have muscular walls (usually only one to two layers of smooth muscle cells) and are the primar ...

s, which lead to the

capillaries A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...

that surround the

pulmonary alveoli A pulmonary alveolus (plural: alveoli, from Latin ''alveolus'', "little cavity"), also known as an air sac or air space, is one of millions of hollow, distensible cup-shaped cavities in the lungs where oxygen is exchanged for carbon dioxide. A ...

Structure

The pulmonary arteries are

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s that carry systemic venous blood from the right ventricle of the heart to the

microcirculation The microcirculation is the circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within organ tissues. The microvessels include terminal arterioles, metarterioles, capillaries, and venules. ...

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 become

s, eventually narrowing into the capillary microcirculation of the lungs where gas exchange occurs.

Pulmonary trunk

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 A ventricular outflow tract is a portion of either the left ventricle or right ventricle of the heart through which blood passes in order to enter the great arteries. The right ventricular outflow tract (RVOT) is an infundibular extension of ...

right ventricle A ventricle is one of two large chambers toward the bottom of the heart that collect and expel blood towards the peripheral beds within the body and lungs. The blood pumped by a ventricle is supplied by an atrium, an adjacent chamber in the uppe ...

(also known as infundibulum or conus arteriosus. The outflow track runs superiorly and to the left, posterior to the

pulmonary valve The pulmonary valve (sometimes referred to as the pulmonic valve) is a valve of the heart that lies between the right ventricle and the pulmonary artery and has three cusps. It is one of the four valves of the heart and one of the two semilunar v ...

. The pulmonary trunk bifurcates into right and left pulmonary arteries below the

arch of aorta The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins a ...

and in front of the left main bronchus. Pulmonary trunk is short and wideapproximately in length and - in diameter. The pulmonary trunk splits into the right and the left main pulmonary artery. The left main pulmonary artery is shorter than the right, 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 proximal

descending aorta In human anatomy, the descending aorta is part of the aorta, the largest artery in the body. The descending aorta begins at the aortic arch and runs down through the chest and abdomen. The descending aorta anatomically consists of two portions o ...

by the

ligamentum arteriosum The ligamentum arteriosum (arterial ligament), also known as the Ligament of Botallo or Harvey's ligament, is a small ligament attaching the aorta to the pulmonary artery. It serves no function in adults but is the remnant of the ductus arteriosus ...

. 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.

Branches

The left main pulmonary artery then divides into two lobar arteries, one for each lobe of the left lung. At the right

root of the lung The root of the lung is a group of structures that emerge at the hilum of each lung, just above the middle of the mediastinal surface and behind the cardiac impression of the lung. It is nearer to the back (posterior border) than the front (ant ...

, 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. The right and left main pulmonary (lungs) arteries give off branches that supplies the corresponding

lung lobe The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of ...

s. In such cases it is termed lobar arteries. The lobar arteries branch into segmental arteries (roughly 1 for each segment). Segmental arteries run together with segmental bronchi, at the posterolateral surfaces of the bronchi. These in turn branch into subsegmental pulmonary arteries. These eventually form intralobular arteries. The pulmonary arteries supply the alveoli of the lungs. In contrast,

bronchial arteries In human anatomy, the bronchial arteries supply the lungs with nutrition and oxygenated blood. Although there is much variation, there are usually two bronchial arteries that run to the left lung, and one to the right lung and are a vital part o ...

, that has different origins, supply the bronchi of the lungs.

Development

The pulmonary arteries originate from the

truncus arteriosus The truncus arteriosus is a structure that is present during embryonic development. It is an arterial trunk that originates from both ventricles of the heart that later divides into the aorta and the pulmonary trunk. Structure The truncus arterio ...

and the sixth

pharyngeal arch The pharyngeal arches, also known as visceral arches'','' are structures seen in the embryonic development of vertebrates that are recognisable precursors for many structures. In fish, the arches are known as the branchial arches, or gill arche ...

. The truncus arteriosus is a structure that forms during the development of the heart as a successor to the

conus arteriosus The infundibulum (also known as ''conus arteriosus'') is a conical pouch formed from the upper and left angle of the right ventricle in the chordate heart, from which the pulmonary trunk arises. It develops from the bulbus cordis. Typically, the i ...

. By the third week of

development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

, the

endocardial tubes The endocardial tubes are paired regions in the embryo that appear in its ventral pole by the middle of the third week of gestation and consist of precursor cells for the development of the embryonic heart. The endocardial heart tubes derive from th ...

have developed a swelling in the part closest to the heart. The swelling is known as the

bulbus cordis The bulbus cordis (the bulb of the heart) is a part of the heart development, developing heart that lies ventral to the primitive ventricle after the heart assumes its S-shaped form. The superior end of the bulbus cordis is also called the conotrun ...

and the upper part of this swelling develops into the

. The structure is ultimately mesodermal in origin. During development 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 a

septum In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatri ...

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 the

aorta The aorta ( ) is the main and largest artery in the human body, originating from the left ventricle of the heart and extending down to the abdomen, where it splits into two smaller arteries (the common iliac arteries). The aorta distributes ...

and pulmonary arteries. During

early development Prenatal development () includes the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal devel ...

, the

ductus arteriosus The ''ductus arteriosus'', also called the ''ductus Botalli'', named after the Italian physiologist Leonardo Botallo, is a blood vessel in the developing fetus connecting the trunk of the pulmonary artery to the proximal descending aorta. It a ...

connects the pulmonary trunk and the

aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...

, allowing blood to bypass the lungs.

Function

The pulmonary artery carries deoxygenated blood from the

to the lungs. The blood here passes through

adjacent to

alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit. Uses in anatomy and zoology * Pulmonary alveolus, an air sac in the lungs ** Alveolar cell or pneumocyte ** Alveolar duct ** Alveolar macrophage * ...

and becomes oxygenated as part of the process of

respiration Respiration may refer to: Biology * Cellular respiration, the process in which nutrients are converted into useful energy in a cell ** Anaerobic respiration, cellular respiration without oxygen ** Maintenance respiration, the amount of cellul ...

. In contrast to the ''pulmonary arteries'', the

supply nutrition to the lungs themselves.

Pressure

The pulmonary artery pressure (PA pressure) is a measure of the

blood pressure Blood pressure (BP) is the pressure of circulating blood against the walls of blood vessels. Most of this pressure results from the heart pumping blood through the circulatory system. When used without qualification, the term "blood pressure" r ...

found in the main pulmonary artery. This is measured by inserting a

catheter In medicine, a catheter (/ˈkæθətər/) is a thin tube made from medical grade materials serving a broad range of functions. Catheters are medical devices that can be inserted in the body to treat diseases or perform a surgical procedure. Cath ...

into the main pulmonary artery. The mean pressure is typically 9–18 mmHg, and the

wedge pressure The pulmonary wedge pressure (PWP), also called pulmonary arterial wedge pressure (PAWP), pulmonary capillary wedge pressure (PCWP), pulmonary artery occlusion pressure (PAOP), or cross-sectional pressure, is the pressure measured by wedging a pulm ...

measured in the

left atrium The atrium ( la, ātrium, , entry hall) is one of two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular valves. There are two atr ...

may be 6–12 mmHg. The wedge pressure may be elevated in left heart failure,

mitral valve stenosis Mitral stenosis is a valvular heart disease characterized by the narrowing of the opening of the mitral valve of the heart. It is almost always caused by rheumatic valvular heart disease. Normally, the mitral valve is about 5 cm2 during d ...

, and other conditions, such as

sickle cell disease Sickle cell disease (SCD) is a group of blood disorders typically inherited from a person's parents. The most common type is known as sickle cell anaemia. It results in an abnormality in the oxygen-carrying protein haemoglobin found in red b ...

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. As can be measured on a CT scan, a diameter of more than 29 mm diameter is often used as a cut-off to indicate pulmonary hypertension. In chest X-rays, diameter of descending pulmonary artery more than 16 mm indicates pulmonary hypertension. This may occur as a result of heart problems such as

heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...

, lung or airway disease such as

COPD Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by long-term respiratory symptoms and airflow limitation. The main symptoms include shortness of breath and a cough, which may or may not produce mu ...

scleroderma Scleroderma is a group of autoimmune diseases that may result in changes to the skin, blood vessels, muscles, and internal organs. The disease can be either localized to the skin or involve other organs, as well. Symptoms may include areas ...

, or thromboembolic disease such as

pulmonary embolism Pulmonary embolism (PE) is a blockage of an pulmonary artery, artery in the lungs by a substance that has moved from elsewhere in the body through the bloodstream (embolism). Symptoms of a PE may include dyspnea, shortness of breath, chest pain p ...

or emboli seen in sickle cell anaemia. Most recently, computational fluid based tools (non-invasive) have been proposed to be at par with the current clinical tests (invasive) of pulmonary hypertension. Pulmonary embolism refers to an embolus that lodges in the pulmonary circulation. This may arise from a

deep venous thrombosis Deep vein thrombosis (DVT) is a type of venous thrombosis involving the formation of a blood clot in a deep vein, most commonly in the legs or pelvis. A minority of DVTs occur in the arms. Symptoms can include pain, swelling, redness, and enla ...

, 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 that becomes lodged in the bifurcation of the pulmonary trunk with extensions into both the left and right main pulmonary arteries is called a ''saddle embolus''. 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 The ascending aorta (AAo) is a portion of the aorta commencing at the upper part of the base of the left ventricle, on a level with the lower border of the third costal cartilage behind the left half of the sternum. Structure It passes obliqu ...

and

trachea The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...

, and the ''right pulmonary artery'' passes dorsally to the ascending aorta, while the ''left pulmonary artery'' passes ventrally to the

. 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

References

External links

* – "Heart: The

Pericardial sac The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...

and

Great vessels Great vessels are the large vessels that bring blood to and from the heart. These are: *Superior vena cava *Inferior vena cava *Pulmonary arteries * Pulmonary veins *Aorta Transposition of the great vessels is a group of congenital heart defec ...

" * – "Heart: Openings of Great Vessels into the Pericardial Sac" * – " Mediastinal surface of the

right lung The lungs are the primary Organ (anatomy), organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the vertebral co ...

" * – "Mediastinal surface of the

left lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

" * {{DEFAULTSORT:Pulmonary Artery Arteries of the thorax