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The veins act as a blood reservoir, because of the ease of distending them. 55-60% of blood is in systemic veins which is important for blood pressure. The volume of blood returned to the right atrium of the heart per minute is called the venous return. Generally venous return is equal to cardiac output, due to the closed system of the circulation, except for minor transient periods. A number of factors affecting the venous return are: Smooth muscle: Due to presence of smooth muscle, the diameter of the veins can be altered by sympathetic discharge(normally vasoconstrictive), adrenaline and angiotensin II (cause venoconstriction). But because the diameters of veins are large, venoconstriction has little effect on peripheral resistance. Elasticity of the heart: If the elasticity decreases, then the ability to fill the heart is reduced. valves: one way valves in the veins (not in large veins) ease blood flow to heart. Muscle pump: When muscles, particularly leg muscles contract, the thin walled veins are squeezed and the blood is forced towards heart, when muscles relax, blood enters the veins, but only from the arterial side. This is an important mechanism for facilitating venous return. Respiratory pump: Breathing in causes negative pressure in thorax causing a suction effect, i.e. the pressure gradient pushing blood towards the right atrium is increased, thus more blood returns to the heart, which means that inspiration leads to an increase in venous return. The opposite occurs with expiration, and venous return is decreased. Gravity: Opposes return of blood from the periphery during sitting or standing. The effect is lost when we lie down. Blood pressure at venous end of capillary: An increased pressure at the venule end of the capillary reduces venous return, because the pressure difference between the right atrium and the peripheral veins is reduced. Similarly a decrease in pressure at the venule end would increase venous return. Right atrial pressure: Is the inflow pressure for the heart. It is a function of the amount of blood returned to the heart and the pumping ability of the heart. Its value at rest is normally close to zero but can also become negative (between -4 to 5 mmHg). Its value is increased by blood volume, a weak heart, rapid increase in venous return. Its value is decreased by lower blood volume and a strong heart. The lower the pressure the greater the venous return (due to suction effect), but there is a limit to the increase in venous return because veins are collapsible.
What else can I help you with?
What is the medical term meaning abnormal circulatory condition characterized by decreased return of venous blood from the legs to the trunk of the body?
venous insufficiency
Who discovered that venous valves help aid in the return of blood to the heart?
William Harvey
What happens when there is a reduction to the blood returning to the heart does it increase?
Venous return (VR) is the flow of blood back to the heart. Under steady-state conditions, venous return must equal cardiac output (CO) when averaged over time because the cardiovascular system is essentially a closed loop.if systemic venous return is suddenly decreased, right ventricular preload decreases leading to an decrease in stroke volume and pulmonary blood flow.Decreased pulmonary venous return to the left atrium leads to decreased filling (preload) of the left ventricle, which in turn decreases left ventricular stroke volume by the Frank-Starling mechanism.In this way, a decrease in venous return to the heart leads to an equivalent decrease in cardiac output to the systemic circulation.
Where do venous valves channel blood?
They prevent back flow and help to return blood to the heart.
Why does walking prevent stagnation of blood in the legs?
The venous circulation of the legs requires muscle contractions to assist with blood return. Walking helps provide this muscle contraction.
What is the function of venous valves?
Valves aid in venous return by preventing the back flow of blood.
Tip the bed head down for venous return?
No, lift legs for venous return. Make sure legs are above heart. You do this for shock or bleeding.
What will the venous return be if the cardiac output is 7.5 liters?
Venous return must always match cardiac output. So a CO of 7.5 l/m mill mean a VR od 7.5 l/m
How does the venous return mechanism work?
pressure gradient , gravity , skeletal muscle pump, thoracic pump and cardiac suction would be the mechanisms for venous return.
How posture affect venous return?
Posture significantly affects venous return, which is the flow of blood back to the heart. In an upright position, gravity can impede venous return from the lower extremities, potentially leading to pooling of blood in the legs. Conversely, lying down or elevating the legs can enhance venous return, as gravity assists blood flow back to the heart. Additionally, muscle contractions during activities like walking help pump blood through the veins, further improving venous return.
What increases stroke volume?
increase venous return
Why the jugular venous pressure falls during inspiration?
because the endothoracic pressure is decreased and the venous return to the heart is increased.
What is return blood?
Return blood, most likely, refers to the venous blood that is returned to the heart.
What factors affect venous return to heart?
Venous return to the heart is influenced by several factors, including venous pressure, the pressure gradient between the veins and the heart, and the functioning of the valves within the veins. Additionally, muscle contractions during physical activity help propel blood back to the heart, a phenomenon known as the muscle pump. Respiratory movements also play a role, as changes in thoracic pressure during breathing can facilitate venous return. Lastly, blood volume and overall vascular resistance can impact the efficiency of venous return.
What is the effect of prolonged sitting on venous return?
Prolonged sitting can lead to decreased muscle activity, causing a decrease in venous return from the extremities back to the heart. This can result in blood pooling in the legs, increasing the risk of developing blood clots and other venous issues. It is important to take breaks, move around, and elevate the legs periodically to help improve venous return while sitting for long periods.
What factor affecting stroke volume is determine by venous return?
contractility
What two things aide venous return within the body?
wht?
