Blood Pressure in Arteries, Veins and Capillaries

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H

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I'm looking at this for Biology A level. Hows the nursing going?

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[@farzanaatta3978]

Amazing explanation, you explained everything in detail, i m glad you posted this, thanxxxx a ton!

[@AKLECTURES]

awesome! you're welcome :-)

[@قصصالأنبياء-ب2ك]

Wow very informative yet absolutely simple

[@mariannamorgan9960]

How would you describe the compliance of the capillaries? Thank you so much for your excellent videos and your admirable work !

[@saritameena2302]

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[@AyaNabilKhasibAliAlAjmi]

thank you. Great explanation

[@BohdanK82]

Good lectures. Should not velocity increase in arterioles due to smaller diameter, as pressure drops (according to Bernoulli’s effect)?

[@AshishGupta-pp4sv]

Excellent instruction - Thank you for taking the time

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[@lea51294]

This should definitely have more than 500 views! You're a very good teacher (actually more than just a good teacher you are a very good "pédagogue" (word in french untranslatable in english)). I wish you would be the one teaching my courses. What majors have you studied to know all that?

[@AKLECTURES]

Lea N Hi, thanks for that Lea, I appreciate your positive feedback :) I majored in applied math and physics, and took ton of courses in other sciences. What are you focusing on in school?

[@lea51294]

I'm a second year medecine student (in France you can begin medecine university right after graduation... and finish them when you're 30) We did learn physics of fluids the first year but you explained it in a much more explicit and biologically related way It really helped me to have a deeper and cleared explanation on the physiological basis of vascular diseases.

[@nellyhoffman6194]

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[@selfhelp1019]

it made my my clearer now

[@hp8309]

For the diagram, it makes sense the way he explained it. But I'm confused as to why the pressure in the veins is lower than in the arteries because veins have a great amount of skeletal muscle to be able to increase the pressure and push it back up to the heart. Is the pressure generated by skeletal muscle in the vein enough to make blood return to the heart, but still lower than in the ateries?

[@gambart2002]

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[@shariqmajeed8709]

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[@joshmorehouse335]

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[@thekillerphython]

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[@nihalk686]

Wouldn't the velocity be higher in the arterioles, but the pressure be lower? I am thinking about the continuity equation A1V1=A2V2. If the area is decreased, the velocity is increased, so the pressure is decreased.

[@shashimoghe3920]

Dr sir very great explanation in such a easy way appreciate your efforts thanks 12/06/2021

[@AtuhaireMoreen-h8w]

Amaising

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thanks for your lecturer

[@SuperLika17]

simply the best

[@medic8038]

That was so useful

[@dyoomah17]

Can I determine the pressure by the diameter ? I always ask a question and connot found answer .. why the arterioles have lower pressure than arteries , it should have higher pressure because it has smaller diameter and higher resistance so more pressure exerted on the wall . This is according to what I studied in physics when the diameter decrease the pressure increase . Can you clarify this for me please !

[@tarunkakumanu9561]

+dyoomah17 It's because the area they are referring to is equal to the "total cross sectional area" of all arterioles. As arteries branch out, you have lots of little circles and the total cross sectional area increases. As area increases, as you already know, pressure decreases.

[@dyoomah17]

Tarun Kakumanu thank you so much

[@marks7386]

You many,many many more miles of arterioles than veins ,capillaries,arteries.remember you have 60,000 miles thats two and a half times around the earth

[@jakekieserman1594]

how come the continuity equation does not apply to the arterioles? wouldn't having a smaller cross sectional area increase velocity? or is cross sectional arteriole area very high?

[@Pianomaster05]

First remember that flow and velocity are different. Flow is volume/time; velocity is distance/time. With arterioles, you have to take 2 different equations into consideration. Flow is always constant, because the volume of blood is not changing. Ohm's law can be used by stating Flow = Pressure/Resistance: since flow remains constant, if resistance increases, pressure HAS to decrease, to make the flow remain the same. Now regarding velocity, the cross-sectional area of arterioles is higher than arteries (but not higher than capillaries). But we can use the continuity equation here, to say that Flow is constant, cross-sectional area increases (even though the diameter of each individual arteriole decreases, there are a greater number overall of arterioles that branch out, just like the capillaries, but to a smaller extent), so velocity decreases. Approach pressure and velocity separately, since they are in different equations. And keep flow and velocity separate as well. Hope this helps someone!

[@dinsenera5521]

thank you Zach. your comment has helped me greatly

[@tunneltrance]

flow and velocity aren't separate. They are linked by the continuity equation. (area1)(velocity1)=(area2)(velocity2) so square meters multiplied by (m/s) equals vol/time which is the flow rate... My question is, doesn't a slower moving fluid generate more pressure on the walls of a tube? I understand how velocity has to decrease but why isn't overall pressure increasing?

[@zaharaf5035]

@@dinsenera5521 How does resistance vs pressure have inverse proportional?!

[@livingbysummer]

At 5.00min are you meant to say that increased resistance = increased pressure? (not decreased pressure)

[@adillahgul]

I have a question tha either velocity of vena cava is higher or capillary??

[@bharathrajaram1696]

Why there is high resistance in arterioles since cross sectional area is high please reply

[@eni6795]

I love you, seriously

[@SandraGarcia-sn8sy]

I have exactly the same doubt as dyoomah17 When there is a smaller diameter, there is more resistance, blood pressure is supossed to rise because more pressure is needed to keep the blood flowing. Still it is true that the blood pressure decreases in arterioles, but why is this? Also, resistance is related to the lenght of the vessel, the longer the way, the more resistance... I know there is an explanation, I just can't figure it out!

[@shahriaranzum]

Sandra García blood velocity in arterioles is very much lower than that of aorta.This may be the cause of not increase in pressure.

[@nanosciencebyjalal3793]

please keep in mind that even though the diameter of capollaries decrease, their number increases compared to the number of arteries and arterioles.... so this will let the same amount of blood to flow through a relative higher number of TUBEs (let's say) and that will lead to lower pressure and velocity

[@Priyanka-ds8tv]

As the diameter decreases,resistance increases,velocity of the blood flow decreases and hence the pressure decreases

[@abeeraldhuhli2523]

Thanks so much keep going

[@SANDRA-ho2xu]

what is the average length of a lysozyme? I need help urgently. Thank you

[@vbt1992]

-So in arteries the recoil ability due to Smooth muscle in Tunica media being Higher , causes Higher pressure hence higher Velocity( propelling the blood) - In cappillaries the surface area is Very big so the speed/velocity decreases -In Vein the recoil is low, hence pressure is low hence velocity is low . Did i get it correctly? , and do the cappillaries still have the slowest Velocity ? THANK YOU!

[@vbt1992]

I Already did the exam from what i understand : **Compliance ability of a vessel to expand under a given pressure . **Rule : Compliance vs Pressure , pulse and speed are inverse proportional ! -Arteires have bigger tunica media( contianing smooth muslce) which gives them less compliance then veins ( who have a smaller Tunica media hence less Smooth muscle ) ------> if we put same amount of pressure to Lumen of vein and arteries , Veins wil Expands MORE , because they have higher compliance!!! -----------> Concerning the Cappillaries , they have a very large surface area according to physics : Pressure = Force / Area so as area increases, Drastically ( to allow exchange) . the PRessure Will go down , not Necc to High compliance but to High Surface Area :) Hope that Helped!

[@vbt1992]

+Basma Chentouf Hi Again :) *Well the Theory Goes The Following, it will be somewhere between those 2 explanations : 1- Resistance( by smooth muscle) representive in a way , The ANTI-Compliance , becasue the higher the resistance ------> the Lower the compliance the higher the pressure . 2-Think of Water in a Tube yes the tube might be long and yes vessels , esp Veins contain larger amounts of blood at any given time( veins are the resevoir) , but becuase they are Squeezed in small lumen with High resistance and Low Compliance , they will have High PRessure!!! Cappillaries is like the water exiting the Tube it will spread much randomly ( non linear like in tube lumen) so it will tend to slow down . Analogy: Sink Water, you turn on Water( Hot or cold) the water in the pipes in water rushing into your sink (very fast high pressure, probably large surface area of all tube in the building) but as soon as water exists into your Sink it will lose its momentum, Speed and pressure because it is not compressed( does not face resistance anymore ) . Now you will also ask (if you reached this part) why hte pressurei n vein is much smalelr then arteries thats due to High Complianceexpandibility of vein being much higher then that of arteries . IF you Still didnt Fully Grasp it memorize this ( as rules) : -Smooth muscle----> provides resistance , anti compliance( compliance inverse proportional to pressure and speed) -Arteires having more smooth muscle have lower compliance ,( just like stronger metal pipe , vs Vein as plastic pipe) the blood will be movng much faster -Cappillaries ( as your sink) water leaves the tube into a much wider area , so the pressure falls ,as well as speed - Veins: having less smooth muscle , have higher Compliance ( ability to expands) ( Platic pipe) so the pressure will be much less then in arteries . With age Arteries stiffer ( Arterosclerosis) make the compliance decrease further , higher speed and higher pressure :)

[@vbt1992]

i would still use the Water in the Sink Analogy water ( blood) runs fast through the pipe( artery) then in sink becomes slower because the area changes from Lumen to a much wider Lumen (say the sink )if you cant understand just take it as it is... it will click later on... those concept took sometime to sink in .... word of advice Understand everyhting but dont let a small detail stop you ...eventually you will understand it ;)

[@gooddoctor6434]

@@BasmaChentouf one capillary has small surface area , but the sum up of all arteries area gives very large surface area!

[@nicolasfaucher1907]

Nice video. I have a question, though (if it's not too late to ask as this video was posted some time ago). At around 5:00 min, you say that the reason why the pressure decreases int the arterioles is that there is more resistance, and resistance decreases pressure. Yet, according to the equation dP = Q x R, resistance actually increases pressure. Later on, you explain that the combined diameter of capillaries is far greater that that of the arteries, explaining why the pressure drops. Wouldn't the same rationale apply to the arterioles, as their combined diameter is greater than that of the combined diameter of the arteries? If so, then one could easily explain the pressure drop by a greater drop in Q than a R increase per vessel, OR, by keeping Q constant and comparing the actual R decrease when all vessels are combined. Have I missed something, here?

[@serenaliangjing3983]

I am also confused about that. I think that the arterioles have lower pressure because their collective cross sectional area increases and therefore by conservation of flow, V decreases. I don't think his statement about resistance was correct there. Not sure if you have resolved this since then.

[@akin8031]

Perfect!

[@saifmalik6724]

but why we feel pulse in arteries but not in veins?

[@thefenerbahcesk4156]

How do veins move blood upward against gravity?

[@AKLECTURES]

Via the pressure gradient set up by the heart.

[@thefenerbahcesk4156]

AK LECTURES thanks

[@thefenerbahcesk4156]

AK LECTURES I thought it was the valves and skeletal muscles though...

[@sciencetech8063]

veins do not thick tunica media, they have thick tunica externa, correct it,

[@Vunami]

correct your grammar thanks

[@shariqmajeed8709]

When u explained capillary u said that for the efficient change rate of flow should be relatively slow then y are u saying Q=AV flow is constant

[@paranjayapokharel2985]

Flow rate is not the same as velocity. Flow rate of our body's blood shouldn't change because we have the same volume of blood in our closed circulatory system. However, the velocity of blood can change as it goes through arteries, arterioles, capillaries, etc. Q=Av shows that in order to maintain constant flow rate (Q), as the cross-sectional area of the capillaries increases, velocity of blood through the capillaries must necessarily decrease.

[@udhavsingh7397]

sir u gays r doing really good and meaking subject so so so simple we love u gays

[@marks7386]

If we have 60,000 miles of blood veins in our body,that means we have at best 10 to 50 miles of arteries that we could (see)..AND THE arterioles ,,,we have 59,000 miles ,that would be leaving 1000 miles for veins and arteries,,, if you could (see) that many ,,,and its this,,, why dont you just say it. instead of making it so complicated to people......😑we have 60,000 miles of vaines,arteries, arterioles your pumping( two tree root systems connected by the arterioles.)...we can see Arteries,veins capillaries easily but arterioles we cant see there so small and there's 59000 miles leaving 10000 for the ones ,or the bigger ,whitch are called veins and so on........

[@SohiniGuha250294]

Hi! I've watched your physics videos. The cardio vascular series are of poor quality. The writings on the board are not legible. :(

[@SohiniGuha250294]

Ooo, they are not legible in the beginning. It clears up later. Thanks

[@nellyhoffman6194]

Shut up ,,,, Go make some videos and show us what u got

[@SohiniGuha250294]

HI! get some brains? Or eyes? And check follow up comments? No? Dont want to? Dont comment! :P

[@nellyhoffman6194]

Poor quality ? Your face is poor quality

[@SohiniGuha250294]

Sure! Atleast I am aware of it! Thanks :*