Regarding The Process Of Blood Circulation In The Heart?
Why if the capacity in the vein is high then the blood returning to the heart is a little
Good morning Aldy, thank you for the question.
Basically a vein is a blood vessel that functions to carry blood flow from peripheral tissue (other body tissue) back to the heart where these blood vessels contain about 70% of the blood in the body. Veins themselves are the most flexible (flexible) blood vessels in the body compared to other blood vessels, which serves to keep the amount of blood flowing into the heart. The ease of veins in adjusting conditions in the body (in this case changes in pressure within the vein) makes venous capacity, ie the total volume of blood in the vein (both stressed volumema and unstressed volume) at a certain pressure, can also change according to changes in pressure. In normal circumstances, where blood volume is normal and no blood flow occurs, veins have their own pressure which is called as circulatory filling pressure / MCFP. There is a contraction in the muscles of venous blood vessels, causing an increase in compressed volumedium in the vein, causing an increase in MCFP.
But to find out exactly how much blood flow returns to the heart (venous return), this is determined by knowing how much systemic filling pressure (MFSP) and also the pressure in the right atrium of the heart.MFSP in normal circumstances, generally has the rate is almost the same as the MCFP, but the MFSP number can be lower or higher, depending on the ventricular function (chambers) of the heart and also changes in the pressure that is in the blood backflow circuit. Based on the graph made by Guyton, a relationship was found where if the pressure of the right heart atrium> compared to MFSP, the venous return would decrease, and vice versa.
But keep in mind that venous return has its maximum value and is affected by pressure volume and also pressure in the vein. In circumstances where there is a limitation in venous return, to meet the needs of cardiac oputput, the body will increase MFSP by decreasing venous capacity (increasing the amount of compressed volume) without making any changes to the total volume of blood in the vein itself.
So from this it can be said that the venous capacity in question can be changed to high or low is the change in the amount of interressed volume and unstressed volume without a change in the total volume of blood in the vein where if the amount of increased volume increases (venous capacity decreases) there will be an increase in MFSP which will help increase the amount of blood flow back to the heart (venous return). But keep in mind that many things can affect the amount of venous return, so venous capacity is not the only thing seen in determining the amount of venous return.
I hope this helps.