Vanderzyden

L,

And what, precisely, is the flaw inherent in "splitting" the heart into four chambers? The human body is far more complex than fish.

There are not two blood "paths". Blood flows through one long, contiguous circuit having systemic (high pressure) and pulmonary (low pressure) sides. Actually, the design is very elegant, now that you prompt me to consider it from another aspect.

The heart is actually two pumps, a primary and and auxilliary. The primary pump is the left side, which pumps the blood "out to the body". The auxilliary pump is the right (pulmonary) side, which keeps the blood going on the last part of the circuit on its return to the lungs.

And yet, these two pumps work in tandem, and they are contained in the same organ. Simply speaking, the pulses of the heart's electrical system provide power to pumps simultaneously. Amazing!

A final note: No one has shown that the elimination of birth defects would be result from a single pump design.


John

[ October 25, 2002: Message edited by: Vanderzyden ]</p>

lpetrich

Vanderzyden:
And what, precisely, is the flaw inherent in "splitting" the heart into four chambers? The human body is far more complex than fish.

The flaw is in the splitting, not in the heart being two sub-hearts.

Why is it necessary to start off as a single heart and have the interior split in two? Why not start off in the split-in-two configuration? Or even start off as two separate hearts?

There are not two blood "paths". Blood flows through one long, contiguous circuit having systemic (high pressure) and pulmonary (low pressure) sides. Actually, the design is very elegant, now that you prompt me to consider it from another aspect.

The two blood paths are paths through the heart, one for each sub-heart.

One interesting question is why a fish does not have similar circulation, but with blood going through the gills instead of through whatever lungs it might have.

Vanderzyden

Why is "splitting" a flaw? On this view, you must judge cell replication (splitting) to be a "flaw".

Two separate pumps are more inefficient, less elegant, and less compact than a tightly integrated dual pump.


John

Jesus Tap-Dancin' Christ

STRAWMAN!

Nice logic. TROLL ALERT.

Jack the Bodiless

Gravity is utterly irrelevant when discussing fetal blood circulation.

The fetus is a fluid-filled container inside another fluid-filled container. We're discussing pumping fluids around inside a bag of other fluids. Any fluid heading up will displace an equal volume and mass of fluid heading down, and vice versa.

Underwater, a person with poor blood circulation floating in an upright position will NOT experience symptoms such as lack of blood to the brain or pooling of blood in the legs. Same principle.

...of course, this is why NASA trains astronauts in swimming pools. Assume the fetus is in a weightless environment.

[ October 26, 2002: Message edited by: Jack the Bodiless ]</p>

Dr Rick

Apology accepted; I apologize for insulting you.

<strong> No, it does not. Placement of the umbilical vessels in the thorax instead of the abdomen would not significantantly impact fetal circulatory pressures. The pressures within the fetal circulation are determined by the total capacitance of its components, circulatory fluid characteristics, and the forces generated by the heart.

<strong> The umbilical vessels' capacitance would not be affected by relocation, and they and the placenta are not a pump; relocation as described would have no effect on circulatory pressures.

<strong> There has been no proposed change in pump pressures, blood volumes, or circulatory capacitance, so there would be no effective change in fetal circulatory pressures.

<strong> Absolutely not; none of the changes you assert would occur.

<strong> This objection doesn't make sense: the placenta's blood flow in relation to the heart would not change by placing the umbilical vessels in the thorax instead of the abdomen.

<strong> Absolutely not. It's quite clear that there would be no change in the fluid dynamics of the fetal circulation if the umbilical vessels were moved into the thorax; there would be no need for adding the superfluous valve you propose, either.

<strong> See above.

<strong> The right heart ventricular development would not be adversely affected, humans would find a thoracic button no less aesthetic than an abdominal button if they were used to the former instead of the later, and coronary artery oxygenation would improve because the most oxygenated blood would flow to the aorta before the liver if the umbilical vessels were thoracic; anterograde coronary artery flow occurs only during diastole as a result of aortic compliance. Bringing oxygenated blood right into the thoracic vasculture after it leaves the placenta would cause more highly oxygen-saturated blood to flow into the coronary arteries than occurs with the evolved sub-optimal system that now exists.

<strong> The DA is an adaption necessary to compensate for the evolved inefficiencies of the fetal circulation.

Rick

[ October 26, 2002: Message edited by: rbochnermd ]</p>

Vanderzyden

Actually, that was not the subject of my apology. I never insulted you. Not once. However, I do apologize for making a very specific error. I do appreciate your apology. Thanks.

You are correct, the placenta is not a pump. I have agreed that no additional pressure comes up the umbilical vein. However, I think you do not understand the proposal, nor my critique. See below.

These are the changes that would necessary by MrDarwin's design "improvement". Here is his proposal (from page 2):

Clearly, the suggestion is to place the umbilical vein just ABOVE the heart, attaching to the pulmonary artery.

Rick, the PUMP in my diagram is the heart itself. In this design "alternative", there is nothing for the heart to pump. Let me rename the diagram:

&gt; ------- HEART ---- UMB. VEIN ---- UMB. ARTERIES --------&gt; (to heart, via the placenta)

As you can see, both the inflow (umbilical vein) and the outflow (umbilical arteries) are downsteam of the heart. The heart, which is the pump in the system, should be between the influent and the effluent. If not, then the design is not only terribly poor, but effectively inoperable.

Again, the coronary arteries receive blood that is the least oxygenated. Why? Because these arteries--which supply the heart, are located at the root of the aorta, which is BELOW the junction of the umbilical vein.

This is merely an unsubstantiated Darwinist claim. You would need to provide support in order for it to be convincing.

John

[ October 26, 2002: Message edited by: Vanderzyden ]</p>

Jesus Tap-Dancin' Christ

Actually, you DID insult him. Several times.

Dr Rick

Here's how the flow would go in MrD's intelligently designed system:

vena cava&gt;right heart&gt;pulmonary trunk branching into umbilical artery and pulmonary artery &gt;placenta and lungs&gt;umbilical vein joins pulmonary veins&gt;left heart&gt;aorta and coronary arteries&gt;the brain and body&gt;vena cava.

This design obviates the need for the foramen ovale and ductus arteriosus, both of which are necessary now to compensate for the flaws in the evolved fetal circulation. The coronary arteries and the brain would both receive the most oxygenated blood in the intelligently designed system because their arterial blood would not be partially deoxygenated by any other organs as it is now. It would also do away with the potential for umbilical herniation and incarceration because the thoracic cage would be able to prevent organs from pushing through the umbilical tract as they can through the abdominal wall.

That's just one way to improve the system; you could also have the placental vein join the superior vena cava and the umbilical artery branch off of the thoracic aorta and derive the same benefits.

Rick

Dr Rick

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