atrium

Examples of atrium in the following topics:

• Fetal Circulation

  • The blood then moves to the right atrium of the heart.
  • In the fetus, there is an opening between the right and left atrium (the foramen ovale), and most of the blood flows through this hole directly into the left atrium from the right atrium, thus bypassing pulmonary circulation.
  • Some of the blood entering the right atrium does not pass directly to the left atrium through the foramen ovale, but enters the right ventricle and is pumped into the pulmonary artery.
  • At birth, when the infant breathes for the first time, there is a decrease in the resistance in the pulmonary vasculature, which causes the pressure in the left atrium to increase relative to the pressure in the right atrium.

• Blood Flow in the Heart

  • The blood that is returned to the right atrium is deoxygenated and is passed into the right ventricle to be pumped through the pulmonary artery to the lungs for re-oxygenation and removal of carbon dioxide.
  • The left atrium receives newly oxygenated blood from the lungs through the pulmonary veins which is passed into the strong left ventricle to be pumped through the aorta to the different organs of the body.
  • The coronary arteries derive from the aorta and run along the surface of the heart and within the muscle to deliver oxygen-rich blood to the myocardium, while the coronary veins remove deoxygenated blood from the heart muscle returning it through the coronary sinus into the right atrium.
  • Deoxygenated blood is received from the systemic circulation into the right atrium, it is pumped into the right ventricle and then through the pulmonary artery into the lungs.
  • Through association with the alveoli the blood is oxygenated in the lungs and returns to the left atrium through the pulmonary veins, before passing into the left ventricle and being pumped around the body.

• Great Vessels of the Heart

  • The adult human heart consists of two separated pumps, the right side (right atrium and ventricle,) which pumps deoxygenated blood into the pulmonary circulation, and the left side (left atrium and ventricle), which pumps oxygenated blood into the systemic circulation.
  • They are the veins that return deoxygenated blood from the body into the heart, emptying into the right atrium.
  • The venae cavae are not separated from the right atrium by valves.
  • The pulmonary veins carry oxygenated blood from the lungs to the left atrium of the heart.
  • Four pulmonary veins enter the left atrium.

• Systemic and Pulmonary Circulation

  • Oxygen-depleted blood from the body leaves the systemic circulation when it enters the right atrium through the superior and inferior venae cavae.
  • The oxygenated blood then leaves the lungs through pulmonary veins, which returns it to the left atrium, completing the pulmonary circuit.
  • Oxygen-rich blood from the lungs leaves the pulmonary circulation when it enters the left atrium through the pulmonary veins.
  • The deoxygenated blood continues through the capillaries which merge into venules, then veins, and finally the venae cavae, which drain into the right atrium of the heart.
  • From the right atrium, the blood will travel through the pulmonary circulation to be oxygenated before returning gain to the system circulation.

• Short-Term Neural Control

  • There are also low-pressure baroreceptors located in the walls of the venae cavae and right atrium.
  • The baroreceptors in the venae cavae and right atrium monitor blood pressure as the blood returns to the heart from the systemic circulation.
  • Normally, blood flow into the aorta is the same as blood flow back into the right atrium.
  • If blood is returning to the right atrium more rapidly than it is being ejected from the left ventricle, the atrial receptors will stimulate the cardiovascular centers to increase sympathetic firing and increase cardiac output until homeostasis is achieved.

• Blood Flow in the Lungs

  • The oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left atrium of the heart, completing the pulmonary cycle.
  • The blood is then distributed to the body through the systemic circulation before returning again to the right atrium.

• Veins of the Thorax

  • Two venae cavae return deoxygenated blood from the systemic circulation to the right atrium of the heart.
  • The inferior vena cava returns blood from the abdomen and lower limbs to the right atrium of the heart.

• Principal Veins

  • Both enter the right atrium of the heart with the superior vena cava carrying blood from the arms, head and thoracic cavity and the inderior vena cava carrying blood from the legs and abdomen.
  • The cardiac veins merge into the coronary sinus which empties directly into the right atrium.
  • The pulmonary veins are large blood vessels which received oxygenated blood from the lungs and return it to the left atrium of the heart.

• Chambers of the Heart

  • The atria are located on the anterior end of the heart, with one atrium on each side.
  • The right atrium receives de-oxygenated 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.
  • The ventricles are located on the posterior end of the heart, beneath their corresponding atrium.

• Operation of Atrioventricular Valves

  • The mitral valve is on the left side of the heart and allows the blood to flow from the left atrium into the left ventricle.
  • The relaxation of the ventricular myocardium and the contraction of the atrial myocardium causes a pressure gradient that allows for a rapid flow of blood from the left atrium into the left ventricle across the mitral valve.
  • The ring contracts at the end of atrial systole due to the contraction of the left atrium around it, which aids in bringing the leaflets together to firm closure during ventricular systole.
  • The tricuspid valve is the three-leaflet valve on the right side of the heart, between the right atrium and the right ventricle, and stops the backflow of blood between the two.