Veins are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal circulations which carry oxygenated blood to the heart. In the systemic circulation, arteries carry oxygenated blood away from the heart, and veins return deoxygenated blood to the heart, in the deep veins.
The circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, that consists of the heart and blood vessels. The circulatory system has two divisions, a systemic circulation or circuit, and a pulmonary circulation or circuit. Some sources use the terms cardiovascular system and vascular system interchangeably with circulatory system.
The superior vena cava (SVC) is the superior of the two venae cavae, the great venous trunks that return deoxygenated blood from the systemic circulation to the right atrium of the heart. It is a large-diameter (24 mm) short length vein that receives venous return from the upper half of the body, above the diaphragm. Venous return from the lower half, below the diaphragm, flows through the inferior vena cava. The SVC is located in the anterior right superior mediastinum. It is the typical site of central venous access via a central venous catheter or a peripherally inserted central catheter. Mentions of "the cava" without further specification usually refer to the SVC.
The azygos vein is a vein running up the right side of the thoracic vertebral column draining itself towards the superior vena cava. It connects the systems of superior vena cava and inferior vena cava and can provide an alternative path for blood to the right atrium when either of the venae cavae is blocked.
In human anatomy, the abdominal aorta is the largest artery in the abdominal cavity. As part of the aorta, it is a direct continuation of the descending aorta.
The atrium is one of the 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 mitral and tricuspid heart valves.
The renal veins in the renal circulation, are large-calibre veins that drain blood filtered by the kidneys into the inferior vena cava. There is one renal vein draining each kidney. Each renal vein is formed by the convergence of the interlobar veins of one kidney.
In human anatomy, the common iliac veins are formed by the external iliac veins and internal iliac veins. The left and right common iliac veins come together in the abdomen at the level of the fifth lumbar vertebra, forming the inferior vena cava. They drain blood from the pelvis and lower limbs.
In humans, the circulatory system is different before and after birth. The fetal circulation is composed of the placenta, umbilical blood vessels encapsulated by the umbilical cord, heart and systemic blood vessels. A major difference between the fetal circulation and postnatal circulation is that the lungs are not used during the fetal stage resulting in the presence of shunts to move oxygenated blood and nutrients from the placenta to the fetal tissue. At birth, the start of breathing and the severance of the umbilical cord prompt various changes that quickly transform fetal circulation into postnatal circulation.
The coronary sinus is the largest vein of the heart. It drains over half of the deoxygenated blood from the heart muscle into the right atrium. It begins on the backside of the heart, in between the left atrium, and left ventricle; it begins at the junction of the great cardiac vein, and oblique vein of the left atrium. It receives multiple tributaries. It passes across the backside of the heart along a groove between left atrium and left ventricle, then drains into the right atrium at the orifice of the coronary sinus.
The term Great veins can refer to either —
The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.
In anatomy, a persistent left superior vena cava is the most common variation of the thoracic venous system. It is present in between 0.3% and 0.5% of the population, and is an embryologic remnant that results from a failure to involute.
The vitelline veins are veins that drain blood from the yolk sac and the gut tube during gestation.
The valve of the inferior vena cava is a venous valve that lies at the junction of the inferior vena cava and right atrium.
The ovarian vein, the female gonadal vein, carries deoxygenated blood from its corresponding ovary to inferior vena cava or one of its tributaries. It is the female equivalent of the testicular vein, and is the venous counterpart of the ovarian artery. It can be found in the suspensory ligament of the ovary.
The testicular vein, the male gonadal vein, carries deoxygenated blood from its corresponding testis to the inferior vena cava or one of its tributaries. It is the male equivalent of the ovarian vein, and is the venous counterpart of the testicular artery.
The lumbar veins are four pairs of veins running along the inside of the posterior abdominal wall, and drain venous blood from parts of the abdominal wall. Each lumbar vein accompanies a single lumbar artery. The lower two pairs of lumbar veins all drain directly into the inferior vena cava, whereas the fate of the upper two pairs is more variable.
In anatomy, the venae cavae are two large veins that return deoxygenated blood from the body into the heart. In humans they are the superior vena cava and the inferior vena cava, and both empty into the right atrium. They are located slightly off-center, toward the right side of the body.
The heart is a muscular organ situated in the mediastinum. It consists of four chambers, four valves, two main arteries, and the conduction system. The left and right sides of the heart have different functions: the right side receives de-oxygenated blood through the superior and inferior venae cavae and pumps blood to the lungs through the pulmonary artery, and the left side receives saturated blood from the lungs.
