The superior pulmonary veins take an oblique inferomedial course whereas the inferior pulmonary veins run horizontally peripherally before taking a more vertical course. They pass through the lung hilum , antero-inferiorly to the pulmonary arteries, forming a short intrapericardial segment, to drain into the left atrium.
The ostia of the inferior pulmonary veins are more posteromedial and the left pulmonary veins being more superior. There is extensive communication with deep bronchial veins within the lung and with the superficial bronchial veins at the hilum. These abnormal foci can be treated with RFA. Variant configurations are more common on the right and include:. There may also be partial anomalous pulmonary venous return PAPVR where the pulmonary veins drain into a structure besides the left atrium and rarely total anomalous pulmonary venous return TAPVR occurs where there is no drainage of pulmonary veins into the left atrium.
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Become a Gold Supporter and see no ads. The wall that separates the left and right side of the heart is called the septum. 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:. Pulmonary hypertension is a condition in which the pressure in the pulmonary veins is elevated. It occurs most commonly with left heart failure, as blood backs up into the veins due to inefficient contractions of the heart.
Several other types of heart disease can lead to pulmonary venous hypertension as well, including conditions such as mitral stenosis. Symptoms can include shortness of breath, swelling of the legs, and fatigue. It is diagnosed with a right heart angiogram, which finds an increase in capillary wedge pressure. The primary treatment is to address the underlying cause of the disease. Pulmonary Vein Thrombosis.
Blood clots may form in the pulmonary vein as with other blood vessels but are quite uncommon. When it does occur, it is often related to a malignancy such as lung cancer. Role in Atrial Fibrillation. The science connecting the pulmonary veins with atrial fibrillation is relatively new. It's thought that the thin layer of myocardial tissue that covers the pulmonary veins can be the focus of atrial fibrillation, with some regions and veins playing a larger role than others.
Pulmonary vein isolation is a procedure that is sometimes done to treat atrial fibrillation. In this procedure, scar tissue is created in the left atrium where each of the four pulmonary enters, which can sometimes control the arrhythmia when other treatments such as medications fail. A complication that sometimes occurs with this procedure is pulmonary venous stenosis discussed above.
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