Vanderzyden

L,

I don't typically respond to you for two reasons:

(1) You refer to me as "Vandie" or something similar
(2) Your posts are often highly tangential and cryptic
(3) I often have no idea what to say to you in response.

Regarding your particular claim here: please explain what evidence supports:

1. that there are flaws inherent in the aortic arch design
2. embryonic--or general--homology is indicative of trans-species modified common descent
3. the (human) CV system is somehow "reorganized"


John

scigirl

Lpetrich,

The picture in my first post here - is this what you mean by aortic arches? <a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=58&t=001585" target="_blank">http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=58&t=001585</a>

If so, are the dotted lines supposed to represent arches that are first created in the embryo, then regress? If so, that's the remodeling story, right?

thanks L,

scigirl

Vibr8gKiwi

Holy moly, this is a first (though I haven't read all of Van's posts). There could be hope.

lpetrich

(VZ: a lot of stuff about the supposed disaster of pumping blood toward the placenta upward instead of downward...)

Except that "pumping upward" occurs for all the rest of the body that is above the heart, so it is not a big disaster.

lpetrich

Yes.

Yes and yes.

scigirl

Yeah, especially getting blood to that one organ. . .it starts with a B, I forget what it's called but I think it's critical for human function...

scigirl

(L - thanks for answering my aortic arch question. BTW - I was reading through placental evolution sites last night and I'm truly fascinated by the subject. They think a virus helped spur the evolution of our placenta - imagine that!)

scigirl

Vanderzyden,

Your discussions about direction of blood flow - do they take into account the position of the fetus in the uterus (which I believe changes around during the 9 month period)?

scigirl

Vanderzyden

Lpetrich,

I notice that you do not take the time to address the three concerns in my last post. Perhaps you plan to post a detailed rebuttal soon.

Pumping "upward" only occurs for the brain and the region of the thorax that is superior to the heart. Gravity, of course, is a primary factor here. No doubt that is the reason for the small radius of the aortic arch and the placement of the subclavian and carotid arteries. Gravity pulls on the aortic blood flow once it goes downstream of the left carotid.





John

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

lpetrich

Vanderzyden:
I don't typically respond to you for two reasons:

(1) You refer to me as "Vandie" or something similar

Is your skin really that thin? What names have I called you?

(2) Your posts are often highly tangential and cryptic

I think of it as choosing my words carefully. What do you find hard to understand? And what do you want me to clarify?

(3) I often have no idea what to say to you in response.

I'm baffled by that comment.

Regarding your particular claim here: please explain what evidence supports:

1. that there are flaws inherent in the aortic arch design

It's a roundabout way to produce a circulatory system, and it produces some odd vessel connections, like the ductus arteriosus.

Also, the heart chambers must split in two, to split the original blood path into two blood paths. Why doesn't the heart start out with two blood paths to begin with? Doing so would avoid the risk of certain types of birth defects.

2. embryonic--or general--homology is indicative of trans-species modified common descent

That alone may not be sufficient evidence, but it does strongly point in that direction. And even if many homologies were the product of design, what does it say about the designer(s)? At the very least, it suggests a curious lack of imagination and a willingness to settle for awkward kludges.

If we, as a species, are so special, then why were we created with such great anatomical similarity to chimps, and why were we created with fishlike early-embryonic circulation?

3. the (human) CV system is somehow "reorganized"

It gets reorganized from a fishlike configuration as it grows. See the illustration earlier in this thread for details.

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

Vanderzyden

I haven't given this much thought, but some things come readily to mind:

1. An adult human may function for extended periods when inverted

2. There is a tradeoff for the inverted orientation: instead of assisting the blood down the aorta, gravity would assist the blood down the inferior vena cava

3. It would seem that there is one more benefit in shunting the blood away (via the ductus arteriosus) from the lungs since the blood will tend to "pool" in the head and upper thorax of the baby.


John