Is this correct?

[Deepa100]

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Here is a paragraph from my TPR bio:
"Small increases in left atrial pressure have very little effect on the pulmonary circulation because pulmonary veins can dilate, accommodating the extra blood. However, if the pressure in the left atrium increases above a certain level, hydrostatic pressure in the capillaries increases and forces the fluid out of the capillaries into the surrounding lung tissue"


Is this using "left atrium" in stead of "right atrium"?
I thought the blood would enter the pulmonary circulation from the right ventricle via the pulmonary artery.😕

 

[Kaustikos]

Here is a paragraph from my TPR bio:
"Small increases in left atrial pressure have very little effect on the pulmonary circulation because pulmonary veins can dilate, accommodating the extra blood. However, if the pressure in the left atrium increases above a certain level, hydrostatic pressure in the capillaries increases and forces the fluid out of the capillaries into the surrounding lung tissue"


Is this using "left atrium" in stead of "right atrium"?
I thought the blood would enter the pulmonary circulation from the right ventricle via the pulmonary artery.😕

It helps to think backwards on this one. Build up of pressure near the end (atria) causes dilation of the veins, the ones sending the fluid, to accomodate the pressure buildup at the atria. BUT if it gets too big, the fluid will flow into lung tissue through the capillaries.

I could be wrong, but I think that's how they want you to interpret it as. The atria is receiving the blood from pulmonary circulation and if you just think of the atria as another pipe section added to the pulmonary veins, it makes more sense conceptually. The build up in pressure causes the veins to accomodate by dilation. But if the pressure exceeds a critical value downstream (Atria) then the hydrostatic pressure increase causes fluid to go into the capillaries. I think that's how pulmonary edemas form.

 

[Heyeon]

I think they are right. Remember that the pulmonary artery gets DEOXYGENATED blood and hence it comes from the right ventricle but the oxygenated blood that the capillaries receive come from the left ventricle thru the aorta and hence pressure changes in the left will influence capillary BP

 

[Deepa100]

It helps to think backwards on this one. Build up of pressure near the end (atria) causes dilation of the veins, the ones sending the fluid, to accomodate the pressure buildup at the atria. BUT if it gets too big, the fluid will flow into lung tissue through the capillaries.

I could be wrong, but I think that's how they want you to interpret it as. The atria is receiving the blood from pulmonary circulation and if you just think of the atria as another pipe section added to the pulmonary veins, it makes more sense conceptually. The build up in pressure causes the veins to accomodate by dilation. But if the pressure exceeds a critical value downstream (Atria) then the hydrostatic pressure increase causes fluid to go into the capillaries. I think that's how pulmonary edemas form.

Yes, all of this is true. But the staement reads "capillaries in the lung", not "capillaries in systemic circulation". So, do the capillaries in lung also get the oxygenated blood from the left ventricle???

 

[minhaj]

The blood is coming into the lt atrium from the pulmonary vein. Lets say for some reason, like valve dysfunction, all of the blood in the left atrium does not drain into left ventricle. As a result the pressure in the atrium increases, this pressure is transferred to the pulmonary vein, which will withstand the pressure to a certain limit. Once this limit has been crossed blood leaks out and this is what causes pulmonary edema.

 

[Deepa100]

I think they are right. Remember that the pulmonary artery gets DEOXYGENATED blood and hence it comes from the right ventricle but the oxygenated blood that the capillaries receive come from the left ventricle thru the aorta and hence pressure changes in the left will influence capillary BP

But we are talking about capillaries in the lung here. Why would the blood come from the left side?

 

[Kaustikos]

Yes, all of this is true. But the staement reads "capillaries in the lung", not "capillaries in systemic circulation". So, do the capillaries in lung also get the oxygenated blood from the left ventricle???

They mean the capillaries that receive the oxygen from the alveoli. I guess I don't know what you are asking. Capillaries in systemic receive the deoxygenated blood so they go to the right atrium. The buildup in left atrial pressure would cause increases in hydrostatic pressure upstream from the pulmonary veins.

Sorry if I sound like a broken record, but I'm just confused by what you're asking. (probably my fault).

 

[Deepa100]

Actually, I read the original lines again and it does make sense. Blood goes from the pulmonary artery--> pulmonary capillaries--> pulmonary veins-->left atrium-->left ventricle-->aorta-->systemic circulation.

So, if the pressure in the left atrium increases, it would cause edema. But can the semilunar valve allow back flow from the left atrium into the pulmonary vein? I didn't think it did.

 

[AsuKa]

Actually, I read the original lines again and it does make sense. Blood goes from the pulmonary artery--> pulmonary capillaries--> pulmonary veins-->left atrium-->left ventricle-->aorta-->systemic circulation.

So, if the pressure in the left atrium increases, it would cause edema. But can the semilunar valve allow back flow from the left atrium into the pulmonary vein? I didn't think it did.

there are 4 valves in the heart

the 2 are atrioventricular
right atria --> tricuspid --> right ventricle
left atria --> bicuspid --> left ventricle

there are 2 semilunar
right ventricle --> pulmonary valve --> pulmonary artery
left ventricle --> aortic valve --> aorta

there is no valve from the pulmonary vein into the left atrium. so the question of "can the semilunar valve allow back flow from the LA into the PV?" the answer is sure, because it's not functioning at all in that aspect of blood flow.

i will however admit that i don't think the reason for edema is the "back flow" of blood, but rather that the current blood in the lungs can not move forward, so it just leaks out.

the way i would think of it is to pretend youre using a garden hose with tiny little holes in it. normally if there is no pressure build up, the water will just flow forward. but if you stick your thumb in the end of the hose, pressure buildup, and water starts coming out the holes. there is no real "back flow" of blood.

someone let me know if im totally off here? 🙂

 

[Deepa100]

there are 4 valves in the heart

the 2 are atrioventricular
right atria --> tricuspid --> right ventricle
left atria --> bicuspid --> left ventricle

there are 2 semilunar
right ventricle --> pulmonary valve --> pulmonary artery
left ventricle --> aortic valve --> aorta

there is no valve from the pulmonary vein into the left atrium. so the question of "can the semilunar valve allow back flow from the LA into the PV?" the answer is sure, because it's not functioning at all in that aspect of blood flow.

i will however admit that i don't think the reason for edema is the "back flow" of blood, but rather that the current blood in the lungs can not move forward, so it just leaks out.

the way i would think of it is to pretend youre using a garden hose with tiny little holes in it. normally if there is no pressure build up, the water will just flow forward. but if you stick your thumb in the end of the hose, pressure buildup, and water starts coming out the holes. there is no real "back flow" of blood.

someone let me know if im totally off here? 🙂

This makes sense, thanks for the clarification!

 

[Kaustikos]

there are 4 valves in the heart

the 2 are atrioventricular
right atria --> tricuspid --> right ventricle
left atria --> bicuspid --> left ventricle

there are 2 semilunar
right ventricle --> pulmonary valve --> pulmonary artery
left ventricle --> aortic valve --> aorta

there is no valve from the pulmonary vein into the left atrium. so the question of "can the semilunar valve allow back flow from the LA into the PV?" the answer is sure, because it's not functioning at all in that aspect of blood flow.

i will however admit that i don't think the reason for edema is the "back flow" of blood, but rather that the current blood in the lungs can not move forward, so it just leaks out.

the way i would think of it is to pretend youre using a garden hose with tiny little holes in it. normally if there is no pressure build up, the water will just flow forward. but if you stick your thumb in the end of the hose, pressure buildup, and water starts coming out the holes. there is no real "back flow" of blood.

someone let me know if im totally off here? 🙂

I didn't mean to sound like I meant backflow. I just didn't know how to "explain" the concept and I knew there woudl be some discrepancy in my post. If it sounds like I said backflow, it's not my point. My point is what you explained with your garden hose analogy.

 

[AsuKa]

no i think you explained it perfectly kaustikos 🙂, rather my post was directed to deepa100 who asked about backflow