Freethought & Rationalism Archive

Jesus Tap-Dancin' Christ · 10-31-2002, 11:00 AM

Quote:

Originally posted by Vanderzyden:
[QB]Scigirl, DD,

The orientation of the fetus does indeed make a difference. Because of gravity, pressure is greater in the bottom of tube (or sphere, or any hollow object) than at the top. It does not matter if there is fluid on the outside of the object.

Actually, it DOES. I JUST got done doing a fluid dynamics unit in physics. You're dead wrong. The pressure within a closed system (i.e, a tire, your bloodstream, etc) is consistent throughout due to the surrounding pressure.

Quote:

When the baby rotates inside the fluid-filled womb, gravity will always act in the same direction (towards the center of the earth). If the fetus is "head-down", gravity assists blood, down the inferior vena cava, to the heart and places greater pressure on the upper thorax, which in turn helps to push blood up the aorta. When the fetus is "head-up", gravity assists blood down the aorta, as in the adult. If the fetus is horizontal, the pumping load on the heart is significantly reduced, since gravity is not "pulling" on either the influent or the effluent.

Except you're wrong, since gravity will have NO ADDITIONAL EFFECT due to the AMBIENT PRESSURE.

Quote:

I am puzzled: what further explanation is necessary for the aortic arch? I have explained it previously (on the first page):

I am puzzled too. You have no clue as to why you are wrong, but you insist the contrary.

Vanderzyden · 10-31-2002, 12:28 PM

Closed systems allow the analyst to assume the principle of conservation of mass. Gravitational effects still apply, and they are significant.

The following is a biophysics (cardiovascular) excerpt from <a href="http://www.rwc.uc.edu/koehler/biophys/3a.html" target="_blank">this website</a> :

Quote:

There is another pressure variation within the body which occurs when one part of the body is at a different elevation than another. This is called "hydrostatic" pressure, and arises because of the gravitational potential energy of the blood. Essentially, blood that is at a higher elevation has greater potential energy, and it "pushes down" on the blood at lower elevations. In fact, we will often think of pressure as an energy density (energy per unit volume), so we can think of the hydrostatic pressure as a gravitational potential energy density. The hydrostatic pressure difference due to a difference in height is given by

P = r g H,

where r is the density of the fluid (which for blood is 1.05 g / cm 3), g is the acceleration due to gravity and H is the difference in height. If we use cgs units, g = 980 cm / s 2, H is measured in cm and the pressure is then in dynes / cm 2. We will usually ignore the hydrostatic pressure, by assuming that our patients are lying down.

For the purpose of illustrating the units we will be using, however, let's look at the hydrostatic pressure differences in a typical person. We quoted above a healthy diastolic pressure of 80 mmHg. The conversion from mmHg to dynes / cm 2 is 1333 dynes / cm 2 per mmHg.

If the diastolic pressure at the aorta is 80 mmHg, what is the pressure in the neck 20 cm higher, and at the top of the legs 70 cm lower? Converting to cgs units, the pressure at the aorta is 106,640 dynes / cm 2. This indicates the utility of the more practical medical unit of mmHg. The hydrostatic pressure differences are 20,580 dynes / cm 2 for the neck and 72,030 dynes / cm 2 for the legs. These differences convert to 15.4 mmHg for the neck and 54 mmHg for the legs, indicating a pressure variation of almost 70 mmHg over an approximately one meter range of elevation. The resulting pressures are 64.6 mmHg in the neck and 134 mmHg in the legs. The measurement of blood pressure is usually made in the upper arm since it is at approximately the same elevation as the aorta.

This diagram is for free-surface systems, but is completely relevant to our discussion:

I didn't want to get into technical jargon and equations, but I will do what is necessary to explain these concepts. Ask whatever questions you like.

John

[ October 31, 2002: Message edited by: Vanderzyden ]

Asha'man · 10-31-2002, 12:46 PM

Quote:

Originally posted by Vanderzyden:
I didn't want to get into technical jargon and equations, but I will do what is necessary to explain these concepts. Ask whatever questions you like.

Do you understand the concept of buoyancy? What will happen to a balloon filled with water (and no air) when placed inside a larger container of water?

Clutch · 10-31-2002, 01:01 PM

LOL! I just showed up, read the last few posts in the thread, and it's like I never missed a post in the ongoing saga of deliberate obtuseness called Vandervasion. How difficult is it to absorb the following two points?

1) Adult human bodies of the sort described by the website VZ cribbed from are not entirely immersed in amniotic fluid.

2) Unborn fetuses are entirely immersed in amniotic fluid.

Think of filling a large plastic garbage bag with water, grabbing it by the neck, and holding it in place in the air. (You'd need a crane, mind you.) Yes... that's right.. it would break!

Now, think of diving underwater with the same garbage bag. Open it up and drag it a metre or two, so it balloons up, then pinch the neck shut and float with it there, full of water, underwater.

Does its bottom burst out as the water in it is pulled down towards "the center of the earth"? Or does the ambient pressure of the fluid around it prevent this?

Ah, whatever. You folks with the patience for this guy are secular saints; I hope the lurkers appreciate what you're doing on their behalf.

Dr Rick · 10-31-2002, 01:58 PM

If fetal circulation was gravity-dependent, every pregnant woman wanting an abortion could induce one by just by standing on her head for a few minutes, and every pregnant woman that wanted to keep her baby would have to sleep standing up.

Rick

Vanderzyden · 10-31-2002, 02:19 PM

External pressure doesn't matter in these examples.

Let's take the balloon example. Fill it completely with grape juice (let's take as negligible the difference in the densities of pool water and grape juice). Let's place it in a perfectly still pool of water (like the diagram). What happens?

The balloon will sink to the height of the balloon, such that the top of the balloon is flush with the surface of the water. Now, given the equation of hydrostatic pressure, what shall we say about the pressure of the grape juice in the very bottom of the balloon?

Answer: the pressure of the grape juice in the bottom of the balloon will be the same as the pressure of the pool water just outside the bottom of the balloon. Gravity is acting equally on both fluids (which have the same density and are located at the same depth below the surface of the pool). The difference in the pressure of the water at the depth just outside the bottom of the balloon is significantly greater than the pressure 1 centimeter below the surface of water. This difference in pressure is equivalent to the difference between the pressure of the grape juice in the very bottom of the balloon and the pressure of the grape juice inside and 1 centimeter below the top of the balloon.

(PSurfaceW - PLowW) = (PSurfaceG - PLowG) = PDifference

Note: The hydrostatic pressure is uniform for a given depth below the water's surface. Imagine a horizontal plane that cuts through the pool at the depth of submerged balloon. The pressure of the water at all points on this plane will be equivalent to the pressure of the grape juice in the very bottom of the balloon.

The same principle applies to the fetus immersed in amniotic fluid. For the sake of this discussion, let us ignore arterial pressure and the pressure developed by the heart. In this case the hydrostatic pressure of the blood in the head of an inverted fetus would be equivalent to the hydrostatic pressure of the amniotic fluid just outside the skull.

John

[ October 31, 2002: Message edited by: Vanderzyden ]

Vanderzyden · 10-31-2002, 02:26 PM

Quote:

Originally posted by rbochnermd:
If fetal circulation was gravity-dependent, every pregnant woman wanting an abortion could induce one by just by standing on her head for a few minutes, and every pregnant woman that wanted to keep her baby would have to sleep standing up.

Welcome back, Rick.

I am not claiming that the system is fully gravity-fed (i.e. dependent). I am fully aware that the heart is a powerful pump.

Did you read my response to scigirl?

Quote:

If the fetus is "head-down", gravity assists blood down the inferior vena cava to the heart and places greater pressure on the upper thorax, which in turn helps to push blood up the aorta. When the fetus is "head-up", gravity assists blood down the aorta, as in the adult. If the fetus is horizontal, the pumping load on the heart is significantly reduced, since gravity is not "pulling" on either the influent or the effluent.

Also, I look forward to a response--one way or the other--to my five-point argument, which is the second from the top of page eight.

Thanks,

John

Dr Rick · 10-31-2002, 03:43 PM

Quote:

Also, I look forward to a response--one way or the other--to my five-point argument, which is the second from the top of page eight.

Okay John; for whatever it's worth, here it is. Be forewarned, however; it's almost all "the other":

Quote:

Umbilical vein joins SVC-- This configuration could handle the volume of umbilical vein, but it is essentially no different than the CV system as it is now.

The designed one is thoracic; no more hernias or incarcerations, more oxygenated blood going to the head and coronary arteries, and no more foramen ovale or ductus arteriosus.

Quote:

With the superior vena cava (SVC) and inferior vena cava (IVC) both entering the right atrium, we have the same volume and pressure configuration as in the actual CV system (if we ignore small gravitational effects coming down the SVC). You are still combining the blood from the superior and inferior vena cavas into the right atrium. And, while this blood is at low pressure, it is a high volume. In fact, it is the highest volume of blood at any point in the entire CV system (like the return or sump in a mechanical system). Without the foramen avole (FA) and the ductus arteriosus (DA), this entire volume will be pumped into the pulmonary arterial trunk, and yet the lungs are completely compressed!!!

That last part about the flow through the pulmonary trunk is right, but the "highest volume of blood at any point in the entire CV system" isn't.

Quote:

It is clear, then that, in the actual fetal CV system, the FA and DA function as critical bypass valves. They are necessary in a development configuration where (1) the lungs are not yet operational and (2) the pulmonary arteries cannot sustain a high volume of blood (the pulmonary arteries would burst!).

Collapsed/compressed lungs occur in a variety of medical conditions such as pneumothorax and massive pleural effusion; no one has ever "burst" their pulmonary arteries because their lung or lungs had collapsed or compressed, and there is no reason that this would happen in a fetus, either.

Maintainance of physiologic pulmonary artery pressure is not dependent upon expansion of the lungs.

Furthermore, even in medical conditions where the pulmonary artery pressure is increased, such as in large pulmonary embolism or primary pulmonary hypertension, the pulmonary arteries do not rupture unless there is something else intrinsically wrong with them.

Quote:

Therefore, you still need both the FA and DA if the umbilical vein empties into the right side of the heart.

As we all can see, they are unnecessary in the intelligently designed system we are discussing here.

Quote:

Organ ligaments-- Also, you must install a replacement for the ligamentum arteriosum in order to dampen the heavy vibrations of the artic arch and the pulmonary trunk.

The compliance and strength of the ligament arteriosum is negligible compared to the total compliance and strength of the aorta and pulmonary arteries. If the ligament was necessary for structural support or vibrational dampening, no child would ever survive patent ductus arteriosis, and no adult could survive ascending aorta aneurysm surgery.

The ligament can be completely ligated and removed during thoracic surgery with no ill effects. It is just an embryologic remnant that serves no purpose once the DA closes, and would not be necessary if the fetal circulation had been intelligently designed.

Quote:

Similarly, you must also install replacement ligament for the liver. (How would purposeless macroevolution processes make such provisions?).

The falciform ligament is a lax piece of tissue that incorporates the remants of the umbilical vein and does not provide any structural support to the liver whatsoever; that's why it does not have to be re-attached during liver transplantion or other abdominal surgeries. The liver is internally supported by its attachments to the diaphragm via the coronary and triangular ligaments and other connective tissues attached to the hepatic dome, and by its attachments to the hepatic veins, inferior vena cava, and the portal circulation.

Why would an intelligent designer make a purposeless structure such as the falciform ligament?

Quote:

Placement of the umbilicus at a thoracic boundary-- If you agree to place the effluents to the umbilical arteries below the diaphragm, then you must either (1) loop them back towards the thorax--which requires even more strengthening of the heart, or (2) make arrangements for a second umbilicus!

This is not part of our intelligent design.

Quote:

If the fetus is "head-down", gravity assists blood down the inferior vena cava to the heart and places greater pressure on the upper thorax, which in turn helps to push blood up the aorta. When the fetus is "head-up", gravity assists blood down the aorta, as in the adult. If the fetus is horizontal, the pumping load on the heart is significantly reduced, since gravity is not "pulling" on either the influent or the effluent.

So?

St. Rick

[ October 31, 2002: Message edited by: rbochnermd ]

Vanderzyden · 11-01-2002, 07:29 AM

Rick,

Your short answers are not informative. Please elaborate. I also notice that you take time only to attempt to refute very specific points, leaving much of the argument untouched. Why is that?

Quote:

Originally posted by rbochnermd:

J: Umbilical vein joins SVC-- This configuration could handle the volume of umbilical vein, but it is essentially no different than the CV system as it is now.

R: The designed one is thoracic; no more hernias or incarcerations, more oxygenated blood going to the head and coronary arteries, and no more foramen ovale or ductus arteriosus.

How does more oxygenated blood go to the carotids and coronary arteries? How can you ensure us that other complications don't develop in your new configuration? And what makes you so confident that the FA and DA are no longer necessary?

Quote:

Originally posted by rbochnermd:

That last part about the flow through the pulmonary trunk is right, but the "highest volume of blood at any point in the entire CV system" isn't.

Tell us, then, where is the highest VOLUME of blood flow in the CV system? (not pressure, but volume)

Quote:

Originally posted by rbochnermd:

Collapsed/compressed lungs occur in a variety of medical conditions such as pneumothorax and massive pleural effusion; no one has ever "burst" their pulmonary arteries because their lung or lungs had collapsed or compressed, and there is no reason that this would happen in a fetus, either.

OK, if the arteries are indeed resililent enough to avoid bursting, then the large (again, the largest) volume of blood flow must be forced through the right-half of the heart, in a system where the lungs are compressed. Please tell us, Rick, will you increase the size of all the arteries? Will you somehow increase the overall volume of blood in the system when the lungs eventually expand (thus increasing the volume of the overall CV system? Will you somehow shrink the diameter of the arteries as the baby grows? In addition, will you strengthen and disproporionately and dramtically increase the size of the heart. And, what will you do with this over-sized heart in the infant who has started to breathe? Go on, I'm listening.

Quote:

Originally posted by rbochnermd:

Maintainance of physiologic pulmonary artery pressure is not dependent upon expansion of the lungs.

Furthermore, even in medical conditions where the pulmonary artery pressure is increased, such as in large pulmonary embolism or primary pulmonary hypertension, the pulmonary arteries do not rupture unless there is something else intrinsically wrong with them.

I didn't say this. So, you are saying that the pulmonary artery is no different, whether the lungs are compressed or expanded? This doesn't seem right. Pulmonary resistance does play a factor in pulmonary artery pressure. Pulmonary resistance is very high in the case of the fetus, where the lungs are compressed and fluid filled. This resistance decreases dramatically upon the first expansion of the lungs. Also, consider the rare condition of pulmonary hypertension:

Quote:

Hypertension is the medical term for an abnormally high blood pressure. Normal mean pulmonary-artery pressure is approximately 14 mmHg at rest. In the PPH patient, the mean blood pressure in the pulmonary artery is greater than 25 mmHg at rest and 30 mmHg during exercise. This abnormally high pressure (pulmonary hypertension) is associated with changes in the small blood vessels in the lungs, resulting in an increased resistance to blood flowing through the vessels.

This increased resistance, in turn, places a strain on the right ventricle, which now has to work harder than usual against the resistance to move adequate amounts of blood through the lungs.

<a href="http://mdchoice.com/pt/ptinfo/prim-ph.asp" target="_blank">http://mdchoice.com/pt/ptinfo/prim-ph.asp</a>

Quote:

Originally posted by rbochnermd:

As we all can see, they are unnecessary in the intelligently designed system we are discussing here.

This is merely the same old claim, still as yet unjustifiable. I notice, again, that you fail to address my key points:

Quote:

1. Umbilical arteries -- If you branch the umbilical artery anywhere past the apex of the aortic arch, then you are diverting pressure from the carotids and subclavians. In a vertical circulatory system, the lower you place the effluent--in this case, the branch of the umbilical arteries--the more gravity assists the delivery of fluid to the exit, and conversely. So, in the CV system, the closer you place the branching of the umbilical arteries to towards apex (top) of the aorta, the more pressure will need to be diverted from upstream branches in order to push blood out of these arteries. If the effluent is low enough, then gravity will be sufficient, and no pressure diversion will be necessary (as we see in the actual system). If you don't place the umbilical arteries low enough, then you must decrease the diameter of the upper thoracic arteries to lower their pressure requirements. Of course, by doing so, you set off a chain of subsequent design alterations, beginning with the increase in the strength and capacity of the heart. But this is unnecessary if the designer remembers that gravity is a force that is always--and consistently--available.

Note: Observe, in the actual CV system, that the left subclavian artery is positioned precisely at the apex of the arch. In consideration of the foregoing discussion, you can now see why.

You continue to avoid the critical fact of gravity, both for its benefits and its implications. The height over which gravity acts is directly and significantly proportional to hydrostatic pressure. Until you address this central issue, you have done precious little to support your case.

I notice that you do not dispute the assessment of the placement of the left subclavian artery (directly at the aortic apex). Interesting "coincidence", is it not?

Quote:

2. Umbilical vein diverging into one, two, or four pulmonary veins -- How will the small pulmonary veins handle the large volume of blood from the umbilical vein? On which side will you place the junction(s)? Perhaps you will say both. Then, which set will it be--upper or lower? You can see how easy it is for me to envision a huge mess. Certainly the design is a hack job, at best. Even with four small branches from the umbilical vein, you must increase the diameter of the pulmonary veins to accomodate higher volume blood flow coming from umbilical vein. However, this diameter will be too large for the needs of the lungs once the newborn begins breathing, when the lungs will expand and the new requirements will call for low pressure, high velocity blood flow in the pulmonary veins. This cannot be accomplished if these veins have been enlarged previously for fetal circulation. So, while the design critic has provided direct, close proximity access for the placental flow, he has also introduced serious, non-trivial complications. In particular, if we consider the overall CV system, it is clear that four branches--one to each pulmonary vein--are unnecessary (and malfunction-prone) complexity.

You said absolutely nothing about this argument. Again, I ask why? I will tell you: it is because your redesign is no improvement at all. It is far worse! This is why I have been saying that your bold suggestion is outrageous. You, a mere man, criticizing the design of your body, of which you had no say, and which you cannot prevent from dying. There are few things that are more preposterous.

John

[ November 01, 2002: Message edited by: Vanderzyden ]

lpetrich · 11-01-2002, 08:38 AM

Quote:

Originally posted by Vanderzyden:

You said absolutely nothing about this argument. Again, I ask why? I will tell you: it is because your redesign is no improvement at all. It is far worse! This is why I have been saying that your bold suggestion is outrageous. You, a mere man, criticizing the design of your body, of which you had no say, and which you cannot prevent from dying. There are few things that are more preposterous.

O Vanderzyden, that is an absolutely irrelevant argument. Yes, absolutely irrelevant. We don't have to know everything in order to come up with an improvement on a design. Consider how much of our technology outperforms us in some way or another.

Cars have much greater physical strength, speed, and endurance -- and essentially zero basal metabolism (battery internal leakage). And can any of you perform arithmetic as fast as your computers? Or do massive bookkeeping with the efficiency of a computer?

And making us capable of living forever, or even indestructible, is not as easy as Vanderzyden seems to think it is. At heast judging from his calling this a "small matter".

Finally, O Vanderzyden, you have not said much about early-embryo multiple aortas and aortic arches. And vitelline arteries and veins.

10-31-2002, 02:19 PM	#196
Vanderzyden Senior Member Join Date: Jul 2002 Location: California Posts: 694	External pressure doesn't matter in these examples. Let's take the balloon example. Fill it completely with grape juice (let's take as negligible the difference in the densities of pool water and grape juice). Let's place it in a perfectly still pool of water (like the diagram). What happens? The balloon will sink to the height of the balloon, such that the top of the balloon is flush with the surface of the water. Now, given the equation of hydrostatic pressure, what shall we say about the pressure of the grape juice in the very bottom of the balloon? Answer: the pressure of the grape juice in the bottom of the balloon will be the same as the pressure of the pool water just outside the bottom of the balloon. Gravity is acting equally on both fluids (which have the same density and are located at the same depth below the surface of the pool). The difference in the pressure of the water at the depth just outside the bottom of the balloon is significantly greater than the pressure 1 centimeter below the surface of water. This difference in pressure is equivalent to the difference between the pressure of the grape juice in the very bottom of the balloon and the pressure of the grape juice inside and 1 centimeter below the top of the balloon. (PSurfaceW - PLowW) = (PSurfaceG - PLowG) = PDifference Note: The hydrostatic pressure is uniform for a given depth below the water's surface. Imagine a horizontal plane that cuts through the pool at the depth of submerged balloon. The pressure of the water at all points on this plane will be equivalent to the pressure of the grape juice in the very bottom of the balloon. The same principle applies to the fetus immersed in amniotic fluid. For the sake of this discussion, let us ignore arterial pressure and the pressure developed by the heart. In this case the hydrostatic pressure of the blood in the head of an inverted fetus would be equivalent to the hydrostatic pressure of the amniotic fluid just outside the skull. John [ October 31, 2002: Message edited by: Vanderzyden ]</p>

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10-31-2002, 01:01 PM	#194
Clutch Veteran Member Join Date: Oct 2001 Location: Canada Posts: 3,751	LOL! I just showed up, read the last few posts in the thread, and it's like I never missed a post in the ongoing saga of deliberate obtuseness called Vandervasion. How difficult is it to absorb the following two points? 1) Adult human bodies of the sort described by the website VZ cribbed from are not entirely immersed in amniotic fluid. 2) Unborn fetuses are entirely immersed in amniotic fluid. Think of filling a large plastic garbage bag with water, grabbing it by the neck, and holding it in place in the air. (You'd need a crane, mind you.) Yes... that's right.. it would break! Now, think of diving underwater with the same garbage bag. Open it up and drag it a metre or two, so it balloons up, then pinch the neck shut and float with it there, full of water, underwater. Does its bottom burst out as the water in it is pulled down towards "the center of the earth"? Or does the ambient pressure of the fluid around it prevent this? Ah, whatever. You folks with the patience for this guy are secular saints; I hope the lurkers appreciate what you're doing on their behalf.

10-31-2002, 01:58 PM	#195
Dr Rick Veteran Member Join Date: Jul 2000 Location: USA Posts: 5,393	If fetal circulation was gravity-dependent, every pregnant woman wanting an abortion could induce one by just by standing on her head for a few minutes, and every pregnant woman that wanted to keep her baby would have to sleep standing up. Rick

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