Mechanisms of Venous Return, Animation

(USMLE topics, cardiology) Pressure gradient, skeletal muscle pump, gravity, and respiratory pump .
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Venous return is the flow of blood from the periphery back to the heart’s right atrium. Venous return is important because the more blood returns to the heart, the more blood can be pumped out. In other words, venous return is the major determinant of cardiac output.
Venous return is achieved by several mechanisms:
Pressure gradient: the difference between venous pressure and right atrial pressure is the major force driving peripheral blood back to the heart. In fact, venous return can be determined as the venous pressure gradient divided by venous resistance. Factors that increase venous pressure or decrease right atrial pressure, facilitate venous return. In principle, constriction of veins blocks blood flow, increases venous resistance and reduces venous return. However when blood vessels throughout the body are constricted, such as during sympathetic activation, the increased resistance causes blood pressure to rise, and this eventually overrides the increase in venous resistance. As a result, venous return increases.
Skeletal muscle pump: Veins in the arms and legs are surrounded by skeletal muscles. They also have one-way valves in their walls that only open for upward flow. During everyday activities, such as walking, the muscles contract and squeeze blood in the veins upward, toward the heart. The one-way valves prevent blood from flowing down again when the muscles relax. This is one of mechanisms by which physical exercise increases cardiac output to meet the body’s needs.
Gravity: In an upright position, venous blood from the head and neck flows downhill to the heart simply by gravity. Blood from the lower body and limbs, on the other hand, has to overcome gravity to return to the heart. People who stand or sit still for extended periods of time may suffer from venous blood pooling in the legs. This happens when venous pressure is not sufficient to override gravity and venous return is reduced. Because the heart cannot pump more blood than it receives, cardiac output may decrease, sometimes to a dangerous level, and the person may faint. One can prevent this from happening by activating the skeletal muscle pump, either by keeping the legs moving, or by tensing leg muscles periodically.
Breathing, or respiratory pump: during inspiration, the diaphragm moves down, expanding the thoracic cavity, resulting in a decreased intra-thoracic pressure and a subsequent expansion of the lungs. Part of this change in pressure is transmitted across the walls of the heart, lowering right atrial pressure and thus facilitating venous return. At the same time, the descent of the diaphragm also causes an increase in abdominal pressure. As the inferior vena cava passes through both abdominal and thoracic cavities, an increase in abdominal pressure together with a decrease in thoracic pressure squeeze the blood upward, toward the heart. Increasing the rate and depth of breathing is another way the body raises cardiac output during physical exercise.

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[@anthonyadikwu1849]

This is REALLY HELPFUL. Now I have a better understanding of Venous Return. Thank you for putting this up.

[@Alilamedicalmedia]

You're very welcome!

[@CalmVibesVee]

Excellent. So lots of walking, calf raises, with deep breathing. ✅

[@stevenphamphu]

Took them less than 4 minutes to explain a whole section in my anatomy book lol. Thank you!

[@yashosingh3488]

This explained to me in 4 minutes something I have spent 3 years in medical school stumped by. Thank you so much!

[@leodion8251]

This channel is medical fortune

[@nastarannazari5062]

the animation and the choice of words explaining make this channel outstanding and useful. thanks a lot

[@Alilamedicalmedia]

Thanks and welcome!

[@ashitabhasin8434]

This channel is literally amazing AMAZING concise...stuff but relevant plus clear idea of what is going on actually ....giving this flower for the efforts.⚘

[@Alilamedicalmedia]

Thanks :)

[@CONEWRUN]

정맥순환의 원리와 방법이 잘 정리되어 있네요. 좋은 내용입니다.

[@peterashraf2717]

Thank you...this really helped me a lot. I have a question...why is the opening of only 10% of the capillaries maintains the venous pressure and how? Doesn't opening more capillaries mean more blood will flow to the veins?

[@bugathavicky6441]

Am an medical student i can't understand what they said in the anotomy but now I understand by seeing this useful vedio tqs for providing this type of vedios... 😊

[@Shlesha_gautam]

very concise...exactly what I was looking for..thanks a lot....

[@tmtanzimtmmt1598]

Very much helpful, lots of love💓

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this channel is the best

[@zahramohammedhamedalmahroo1548]

I am soo grateful

[@Hilytios]

Now I have an excuse when I sit still and move my leg up and down. "So for your knowlegde it helps with the blood flow." Heh. Now it is time!

[@ridabatool8691]

This video is very much helpful as others. Kindly put the Renal regulation of Blood pressure and Vascular complaince # topics

[@maura2560]

Thank you, thank you, thank you!!!

[@ilsakhan9631]

Thank you so much It was really helpful !!

[@arock8586]

Thank you so much

[@ma.gracielaaquino1726]

Thank you so much

[@MvmtMetz]

Question. Athletes are often fround upon for leaning over, putting their hands on their knees when out of breath or tired from that quick burst of energy they just expended. Coaches are often yelling to their players to not do that. However, based on gravity, wouldn't being slouched over help venous return? Or am I totally missing the point. Please let me know. Nice video, thank you.

[@infinitehomeopathy8351]

Thanks sir very nice analgesics

[@mathis20737]

Thanks, well explained and clear :)

[@shahwaliafghan102]

thanks so much for your efforts please do a video on birth asphyxia

[@ebayanalfaaz149]

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[@AbdulHaseeb-ov6dn]

Resistance is indirectly proportionL to venous return then how can it rise and secondly veins are highly distensible so increase in pressure has little effect

[@MedicusVishalus]

Cardiac Output, completed

[@AK-yu4tf]

Thanks u very much

[@lachireddydeepika8641]

Tq soo much ....💞

[@jefferylee818]

Skeletal muscle pump 1:20

[@medico5567]

Nice

[@Bagerhat-it5wk]

if venous return high,,then blood pressure decrease?

[@rn2445]

How Venous return increases heart rate (without sympathetic activity)?

[@samuellambertmurrayduncan1412]

Stretching of the Sinus node in the right atrium increases its frequency, and thus heart rate! ;)

[@ashleywhispers4331]

So then could restless leg syndrome be a way the body attempts to help itself

[@adacerita2416]

very good , membantu 🫶🏻

[@sertralinadeavena]

According to what it's explained in 1:00, the same can happen in arteries? Why?

[@shreyashreya1328]

No

[@hajar5263]

It's written in my textbook that venous constriction increases venous return because it reduces the venous reservoirs.

[@soumendas6375]

Yep that's true isme sayad galat bola hai inhone

[@malazmirgani8932]

It is true

[@1961-v9k]

There is now a cure for venous insufficiency.

[@bharathrajaram1696]

How venous resistance increase venous return someone please explain clearly

[@ughsirius]

Technically, increasing venous resistance should lower venous return, right? But what basically happens is that increasing venous resistance ends up increasing venous pressure. Since blood has to flow through a route via more resistance, the pressure rises. And this increase in venous pressure has a more marked effect on the venous return - the venous return increases due to the increased venous pressure.

[@AbdulHaseeb-ov6dn]

@@ughsirius but aren't veins highly distensible?and this increase in pressure his little effect on veins?

[@parzhinyusif]

😍😍😍

[@kylebalfada6245]

So not astrology?

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sÓ O bÁSICO