Why pulmonary artery is named so

The lumen of an artery stays open even when blood is no longer filling it, but the lumen of a vein collapses. When blood is no longer filling a pulmonary artery, it stays round; a pulmonary vein, like all other veins, forms an irregular shape as it collapses when empty. So a pulmonary artery is classified as an "artery" because it leads away from the heart, and because its anatomy is that of an artery, enabling it to withstand the high pressure.

The same principle applies to the classification of a pulmonary vein. Although it carries oxygenated blood, anatomically it's a vein. Why are the pulmonary veins called veins if they carry oxygenated blood? Why are pulmonary arteries called arteries if they carry deoxygenated blood? Johnson Z. Jan 30, Veins transport blood towards the heart, while arteries transport blood away from the heart.

Explanation: All veins in the body transport deoxygenated blood to the heart except for the pulmonary veins. Nov 23, Explanation: A comparison between arteries and veins Anatomically they are veins It's true that pulmonary arteries are not like other arteries in one way -- they carry deoxygenated blood. However, they are like any other artery in another way -- they carry blood away from the heart. The lumen of an artery is relatively smaller than the lumen of a vein of the same diameter.

They are each shaped like tubes with a lumen the opening through which blood flows. The left and right pulmonary arteries send blood to the left and right lungs, respectively. The pulmonary trunk and the right and left pulmonary arteries are shaped somewhat like a capital letter "T", with the trunk forming the lower portion and the left and right branches each forming one of the two sides at the top.

There is a valve between the right ventricle of the heart and the pulmonary trunk. This valve, which is composed of two cusps of connective tissue, is structured to open when the heart pumps so the blood can flow from the right ventricle to the pulmonary trunk.

As the heart muscle relaxes, the valves close to prevent blood from flowing backward to the heart. As with all arteries, the walls of the pulmonary arteries have several layers of muscle that allow them to dilate widen and constrict become narrow. This is very different from the walls of veins, which are thinner and less muscular.

Most arteries in the body carry oxygenated blood, but the pulmonary arteries one of two exceptions that instead carry deoxygenated blood. The umbilical arteries, which carry blood in need of oxygen from a developing baby to the mother, are the other. The pulmonary trunk, which is relatively short and wide, is located at the exit of the right ventricle.

This main arterial branch is located above the heart to the left of the ascending aorta. The right pulmonary artery wedges in the aortic arch , behind the ascending aorta and in front of the descending aorta.

The left pulmonary artery extends near the left side of the aorta. These vessels pierce through the pericardium, which is the connective tissue lining around the heart.

Because the heart is on the left side of the chest, the left pulmonary artery is closer to the lung than the right pulmonary artery. After the left pulmonary artery enters the left lung, it divides into smaller branches. The right pulmonary artery courses across the upper chest to enter the right lung. After this point, this artery divides into smaller branches.

Generally, each pulmonary artery divides into three to seven branches. The most common anatomic variations of the pulmonary arteries are variations in the number of arterial branches in the lungs. There are also some rare congenital deformities of the pulmonary arteries:. The pulmonary arteries are part of the pulmonary circulation, which also includes pulmonary veins and pulmonary capillaries. The purpose of the pulmonary circulation is to transfer oxygen and carbon dioxide between the blood in the body and the air that's inhaled and exhaled in the lungs.

The specific role of the pulmonary arteries is to carry blood that's low in oxygen and high in carbon dioxide waste to the pulmonary capillaries of the lungs, where this exchange takes place. When the blood is enriched with oxygen and cleared of carbon dioxide waste, it flows back through your pulmonary veins to your heart's right ventricle. From there, the blood is pumped to the left ventricle and finally dispersed through the aorta to the arteries that carry the oxygen-rich blood throughout the body.

There are two main conditions that affect the pulmonary arteries in adults— pulmonary embolus PE and pulmonary arterial hypertension. Pulmonary arterial hypertension is a rare disease that develops over time. A PE is a blood clot in an artery of the lungs, and it is a medical emergency.

A PE is a condition in which a blood clot lodges in the pulmonary artery, blocking blood flow to the lungs. Symptoms include:. A PE can occur when a blood clot forms in a vein such as in the legs and travels through the heart, eventually becoming lodged in a pulmonary artery. The left heart deals with systemic circulation, while the right heart deals with pulmonary circulation.

The left side of the heart receives oxygenated blood from the pulmonary vein and pumps it into the aorta, while the right side of the heart receives deoxygenated blood from the vena cava and pumps it into the pulmonary vein. The pulmonary vein and aorta also have valves connecting them to their respective ventricle. The heart has its own self-sustaining conduction system that sends nervous impulses to cardiac tissue. The sinoatrial SA and atrioventricular AV nodes are bundles of nerve fibers that form this conduction system.

They are located in the left atrial wall of the heart and send nerve impulses to a large, highly specialized set of nerves called the Purkinje fibers, which in turn send those nerve impulses to the cardiac muscle tissue. These nodes can send impulses to the heart without central nervous system stimulation, but may be influenced by nervous stimulation to alter heart rate.

The heart also has its own blood supply, the cardiac arteries that provide tissue oxygenation to the heart as the blood within the heart is not used for oxygenation by the heart. The heart is enclosed in a double-walled protective membrane called the pericardium, which is a mesothelium tissue of the thoracic cavity. The double membrane of pericardium contains pericardial fluid which nourishes the heart and prevents shock. This composite sac protects the heart, anchors it to surrounding structures, and prevents the heart from overfilling with blood.

The wall of the heart is composed of three layers of different tissues. The outer layer is called the epicardium, or visceral pericardium, since it is also the inner wall of the pericardium. The middle layer of the heart, the myocardium, and contains specialized cardiac muscle tissue responsible for contraction.

Cardiac muscle tissue is distinct from skeletal or smooth muscle because it pumps involuntarily based on conduction from the AV and SA nodes. The inner layer is called the endocardium and is in contact with the blood that the heart pumps. It also merges with the inner lining of blood vessels and covers heart valves. Cardiac tissue is permanent tissue that does not heal or regenerate when damaged. As a result, is prone to scarring and enlargement due to mechanical stress and injury.

The Mammalian Heart : The position of valves ensures proper directional flow of blood through the cardiac interior. Note the difference in the thickness of the muscled walls of the atrium and the left and right ventricle.

The pericardium is a thick, membranous, fluid-filled sac which encloses, protects, and nourishes the heart. The pericardium is the thick, membranous, fluid-filled sac that surrounds the heart and the roots of the vessels that enter and leave this vital organ, functioning as a protective membrane.

The pericardium is one of the mesothelium tissues of the thoracic cavity, along with the pleura which cover the lungs.

The pericardium is composed of two layers, an outer fibrous pericardium and an inner serous pericardium. Membranes of the Thoracic Cavity : A transverse section of the thorax, showing the contents of the middle and the posterior mediastinum. The pleural and pericardial cavities are exaggerated since normally there is no space between parietal and visceral pleura and between pericardium and heart. The fibrous pericardium is the outer layer of the pericardium.

It is composed of dense connective tissue which anchors the heart to the mediastinum of the chest wall.

It prevents the heart from overfilling with blood and protects it from nearby infections by completely separating it from the rest of the thoracic cavity. It is continuous with the outer fibrous layer of the neighboring great blood vessels. The serous pericardium, the inner layer of the pericardium, is composed of two different layers. The outer layer, the parietal layer , is completely adhered to the fibrous pericardium.

The inner layer is known as the visceral layer , which covers and protects the great vessels and heart. The space between the parietal and visceral layers is called the pericardial cavity. The visceral layer is referred to as the epicardium in the areas where it is in direct contact with the heart.

The space between these two serous layers, the parietal and the visceral, is the pericardial cavity, which contains pericardial fluid. The serous pericardium, with its two membranes and the fluid-filled pericardial cavity, provides protection to the heart and a lubricated sliding surface within which the heart can move in response to its own contractions and to the movement of adjacent structures such as the diaphragm and the lungs.

The pericardium is important because it protects the heart from trauma, shock, stress, and even infections from the nearby lungs. The pericardium lubricates the heart and prevents it from becoming too large if blood volume is overloaded though it will not prevent chronic heart enlargement.

Despite these functions, the pericardium is still vulnerable to problems of its own. Pericarditis is the term for inflammation in the pericardium, typically due to infection. Pericarditis is often a severe disease because it can constrict and apply pressure on the heart and work against its normal function.

Pericarditis comes in many types depending on which tissue layer is infected. The heart wall is comprised of three layers: the outer epicardium, the middle myocardium, and the inner endocardium. The heart wall is comprised of three layers, the epicardium outer , myocardium middle , and endocardium inner. These tissue layers are highly specialized and perform different functions.

During ventricular contraction, the wave of depolarization from the SA and AV nodes moves from within the endocardial wall through the myocardial layer to the epicardial surface of the heart. The Heart Wall : The wall of the heart is composed of three layers, the thin outer epicardium, the thick middle myocardium, and the very thin inner endocardium.

The dark area on the heart wall is scarring from a previous myocardial infarction heart attack. The outer layer of the heart wall is the epicardium. The epicardium refers to both the outer layer of the heart and the inner layer of the serous visceral pericardium, which is attached to the outer wall of the heart. The epicardium is a thin layer of elastic connective tissue and fat that serves as an additional layer of protection from trauma or friction for the heart under the pericardium.

This layer contains the coronary blood vessels, which oxygenate the tissues of the heart with a blood supply from the coronary arteries. The middle layer of the heart wall is the myocardium—the muscle tissue of the heart and the thickest layer of the heart wall.

It is composed of cardiac muscle cells, or cardiomyocytes. Cardiomyocytes are specialized muscle cells that contract like other muscle cells, but differ in shape. Compared to skeletal muscle cells, cardiac muscle cells are shorter and have fewer nuclei. Cardiac muscle tissue is also striated forming protein bands and contains tubules and gap junctions, unlike skeletal muscle tissue.

Due to their continuous rhythmic contraction, cardiomyocytes require a dedicated blood supply to deliver oxygen and nutrients and remove waste products such as carbon dioxide from the cardiac muscle tissue. This blood supply is provided by the coronary arteries. The inner layer of the heart wall is the endocardium, composed of endothelial cells that provide a smooth, elastic, non-adherent surface for blood collection and pumping.

The endocardium may regulate metabolic waste removal from heart tissues and act as a barrier between the blood and the heart muscle, thus controlling the composition of the extracellular fluid in which the cardiomyocytes bathe.

This in turn can affect the contractility of the heart. This tissue also covers the valves of the heart and is histologically continuous with the vascular endothelium of the major blood vessels entering and leaving the heart.

The Purkinje fibers are located just beneath the endocardium and send nervous impulses from the SA and AV nodes outside of the heart into the myocardial tissues. The endocardium can become infected, a serious inflammatory condition called infective endocarditis. This and other potential problems with the endocardium may damage the valves and impair the normal flow of blood through the heart. The heart has four chambers.

The two atria receive blood into the heart and the two ventricles pump blood into circulation. The heart is the complex pump of the circulatory system, pumping blood throughout the body for the purposes of tissue oxygenation and gas exchange. The heart has four chambers through which blood flows: two sets of each type of chamber atria and ventricles , one per side, each with distinct functions.

The left side of the heart deals with systemic circulation while the right side of the heart deals with pulmonary circulation. The atria are chambers in which blood enters the heart. They are located on the anterior end of the heart, with one atrium on each side. The right atrium receives deoxygenated blood from systemic circulation through the superior vena cava and inferior venae cavae.

The left atrium receives oxygenated blood from pulmonary circulation through the left and right pulmonary veins. Blood passively flows into the atria without passing through valves.

The atria relax and dilate expand while they fill with blood in a process called atrial diastole. The atria and ventricles are separated by the mitral and tricuspid valves. The atria undergo atrial systole, a brief contraction of the atria that ejects blood from the atria through the valves and into the ventricles.

The chordae tendinae are elastic tendons that attach to the valve from the ventricles and relax during atrial systole and ventricular diastole, but contract and close off the valve during ventricular systole. One of the defining characteristics of the atria is that they do not impede venous flow into the heart.

Atria have four essential characteristics that cause them to promote continuous venous flow:. The ventricles are located on the posterior end of the heart beneath their corresponding atrium.