Freethought & Rationalism Archive

Vibr8gKiwi · 10-30-2002, 11:30 AM

Quote:

Originally posted by Vanderzyden:
The design of the actual fetal and adult CV systems are amazingly elegant and are the best design for the given purpose. The human body is a work of fanstastical wonders.

Which purpose is that? Death by oversized heart, malformed valves, congenital heart defects, heart attack, stroke, clogged arteries, what? Given my family history, I will most likely die from heart disease, despite running 5 miles three times a week, eating right, not smoking, and such. Apparently I missed the reality where the CV system is the best possible design.

[ October 30, 2002: Message edited by: Vibr8gKiwi ]

scigirl · 10-30-2002, 05:09 PM

Vanderzyden,

Read these quotes again:

Quote:

Originally posted by Jack the Bodiless:
[QB]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.

And here:

Quote:

rbochnermd:
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.

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.

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.

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.[/quote]

All this talk about gravity and fetal blood is making my head hurt. The baby moves around during development. Plus the mom is either standing, sitting, or laying down, which moves the fetus around again.

scigirl

scigirl · 10-30-2002, 05:13 PM

Quote:

Originally posted by Vanderzyden:
(How would purposeless macroevolution processes make such provisions?).

Trial and error.

scigirl

Vanderzyden · 10-30-2002, 08:27 PM

Quote:

Originally posted by scigirl:

All this talk about gravity and fetal blood is making my head hurt. The baby moves around during development. Plus the mom is either standing, sitting, or laying down, which moves the fetus around again.

Scigirl,

I'm sorry. What was the point you wanted to make?

(Jack is completely in error, but I won't both replying because another "fight" will start. Most of Rick's objections were lodged against my first "misplaced pump" argument.The others have been well address by my last set of arguments.)

Incidentally, the details of genetics makes my head hurt, too. But it is fascinating, so I know that I will eventually overcome the "pain".

John

[ October 30, 2002: Message edited by: Vanderzyden ]

Doubting Didymus · 10-30-2002, 08:36 PM

Isn't scigirls point pretty obvious?

Gravity has no effect on the circulatory system of a foetus, as the foetus can be in any position and it makes no difference.

So, the 'height' at which you place the blood input is a non - issue.

MrDarwin · 10-31-2002, 05:08 AM

Quote:

Originally posted by Vanderzyden:
MrD,

I expect more from you, given the high confidence that you have displayed here.

...Am I to construe your silence as complete agreement?

John, please scroll to the top of this very page. What part of

Quote:

Originally posted by MrDarwin:
I'm happy to see that the discussion is going on without me, which it will have to continue to do as I simply have no time to participate right now. I will post a couple more comments, and then will have to retire for a while.

don't you get? I simply don't have time to deal with your erroneous, evasive and dishonest nonsense right now. If you address my concerns about your earlier erroneous and unsupported comments, perhaps when I have more time I will come back and address your new ones.

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

scigirl · 10-31-2002, 05:37 AM

Quote:

Originally posted by Doubting Didymus:
Isn't scigirls point pretty obvious?

Gravity has no effect on the circulatory system of a foetus, as the foetus can be in any position and it makes no difference.

So, the 'height' at which you place the blood input is a non - issue.

Thank you DD - that's what I was trying to say.

I'm still waiting for the creationist explanation for aortic arches in a human fetus.

scigirl

Vanderzyden · 10-31-2002, 08:05 AM

MrD,

With that last post, you make it very clear to me that I should be careful of how much time I invest in a dialogue with you.

Obviously, there is so much you should think about--especially concerning this issue. My earlier characterization of your design critique as "outrageous" has been fully reinforced by your inability to substantiate these naked claims.

John

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

Vibr8gKiwi · 10-31-2002, 08:27 AM

This is great, I'm learning so much from Dr. Van. Now I've learned that a fetus must be upright with its heart above its belly or its blood won't pump right. Mommy better stay in the upright position too. And I guess its a very dangerous time for the babies when they reposition themselves upsidedown in the later stages of the pregancy.

Who needs real Doctors when you have Dr. Van?

Vanderzyden · 10-31-2002, 08:28 AM

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. 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.

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

Quote:

This narrow assessment ignores the fact that the heart is located in the extreme anterior (front) of the chest cavity. The aorta has three branches immediately downstream of the exit from the heart. These branches are the brachiocephalic, the left carotid, and the subclavian. The right carotid branches downstream on the brachiocephalic. These arteries supply the brain and the arms, the access points of which are located above and to the rear of the heart. So, there must be some rotation to the posterior to serve the head (through the neck) and the arms (which are connected at the upper posterior of the torso). These parts of the body require less blood supply than the vital organs and the legs, and so do not need to "carry the full cardiac output". In fact, much blood must be supplied to the lower abdomen and the legs. Another oversight concerns the extremities of entire cardiovascular system, also known as the circulatory system. Throughout the entire body, the blood is reoxygenated and returned 180 degrees back towards the heart. Turns in the system are not defects whatsoever!

John

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

10-31-2002, 08:05 AM	#188
Vanderzyden Senior Member Join Date: Jul 2002 Location: California Posts: 694	MrD, With that last post, you make it very clear to me that I should be careful of how much time I invest in a dialogue with you. Obviously, there is so much you should think about--especially concerning this issue. My earlier characterization of your design critique as "outrageous" has been fully reinforced by your inability to substantiate these naked claims. John [ October 31, 2002: Message edited by: Vanderzyden ]</p>

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10-30-2002, 08:36 PM	#185
Doubting Didymus Veteran Member Join Date: Jul 2002 Location: East Coast. Australia. Posts: 5,455	Isn't scigirls point pretty obvious? Gravity has no effect on the circulatory system of a foetus, as the foetus can be in any position and it makes no difference. So, the 'height' at which you place the blood input is a non - issue.

10-31-2002, 08:27 AM	#189
Vibr8gKiwi Senior Member Join Date: Jul 2000 Location: CA, USA Posts: 543	This is great, I'm learning so much from Dr. Van. Now I've learned that a fetus must be upright with its heart above its belly or its blood won't pump right. Mommy better stay in the upright position too. And I guess its a very dangerous time for the babies when they reposition themselves upsidedown in the later stages of the pregancy. Who needs real Doctors when you have Dr. Van?

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