Blinn

And this explains the circuitous route of the recurrent laryngeal nerve. In fish, the nerve has a direct route under the fourth arch. In mammals however, the modification of the arch setup results in the nerve being "dragged" into the mediastinum with the descent of the heart.

Polly Flinders

I'm interested in the original poster's idea about oxygenated blood getting mixed with deoxygenated blood. I've never seen the birth of a baby, but my brother has, and he said the baby was blue until it took its first breath, then the baby's skin gradually turned pink. Doesn't the blueness indicate that fetuses suffer from an oxygen deficiency? It would certainly indicate that in anyone else.

lpetrich

Vanderzyden:
(to MrDarwin)

Design implies a design-er, which implies a mind.


Which could be more than one, which could have limited capabilities, which could be fallible, ...

And I think that predator-prey relations would strongly suggest multiple designers, one to make the predators more efficient at catching prey, and one to make the prey more efficient at not getting caught. And food chains are often deep enough so that the same animal can be both predator and prey -- many plant-eating ones, for example. So there must be a big community of designers, if we are to take this argument seriously.

And "design" may be a misleading term; "architecture" might be better.

scigirl:
Read Lpetrich's excellent summary of the embryological development of the heart. We can yammer away about the "point" or "usefulness" of aortic arches and gill slits ad nauseum but that is not the point.

The point is - their very existence, irrespective of their function indicates and supports our theory of evolutionary history! We evolved from fish, and lo and behold, we have fishy-like hearts at one point in our embryological development.

Vanderzyden will likely respond by accusing us of being philistines who are unwilling to appreciate the marvels of the circulatory system. But when it develops in a roundabout fashion the way it does, one has to ask why design it that way if one can create designs from scratch?

Why have the heart's interior get split in two when it grows when one could make it start out as two separate sub-hearts? Why create those fishlike aortic arches when they will end up being reorganized and partially deleted?

Starboy

DD, Vander is playing you like a violin.

Starboy

Doubting Didymus

Haha... He's had you screaming on more than a few occasions as well, Starboy!

Starboy

I evolve and adapt.

pz

Yeah, yeah...and he'll just reply that architecture implies an Architect. He's that predictable and that vacuous.

Kevin Dorner

"Structure"? "Structural engineer."
"Shape?" "Shaper."
"Form." "Er... former?"

"Form" is therefore a goodie (maybe.) "Former" means something completely different, so the weak analogy of a linguistically similar word implying a connection is lost.

MrDarwin

Since I was apparently a little too terse for Vanderzyden’s liking, and since he asked so nicely I’m expanding a little on what I posted earlier.

Actually, the complexity was precisely the issue: specifically, the unnecessary complexity.

Rick has already kindly pointed out that there are several not only potential but very real defects, which frequently result in very real-life problems, even death. (Meanwhile I note that Vanderzyden has himself offered no such “distinct and significant advantages”.)

I can only assume that Vanderzyden has a reading comprehension problem, so see below.

Such as??? I’m anxiously awaiting Vanderzyden to offer these problems since I apparently didn't see them.

Apparently I wasn’t specific enough. It’s really very simple: if the umbilical cord entered at the chest, i.e., closer to the heart, the umbilical artery could attach to the trunk of the pulmonary arteries, which would normally be taking deoxygenated blood to the lungs. With this attachment, it would take them to the placenta instead to pick up oxygen (and other nutrients). Of course a small amount of blood would still flow to the lungs, as it does in the current system. Meanwhile, the blood returning through the umbilical vein could attach to any one of the pulmonary veins (another odd design feature—why are there 4 pulmonary veins, one from each lung, each with its own entrance to the left atrium?)--or even directly to the left atrium itself--which would normally be bringing freshly oxygenated blood from the lungs. The entire circuit, with the exception of the umbilical vessels, is exactly the same as in the newborn and adult. When blood flow to and from the umbilical cord is shut off, the attachments close (as they do in the current system, except there are fewer of them). The three major advantages of this are that there is no hole in the heart that has to close (one of the major sources of birth defects), no ductus arteriosus to be patent, and no mixing of oxygenated and deoxygenated blood (one of the reason why these defects are so serious in newborns).

Dr. Rick, care to check my work?

And that is relevant precisely how...???

Why is the liver so special? It’s not doing much of anything in the fetus. It doesn’t seem to be a problem for the heart and lungs in the fetal system, which are already getting blood with the lowest concentration of oxygen.

Whereas the way it works now isn't "tricky" or "problematic"?

It’s not a problem as long as the mother’s lungs are providing all the oxygen via the placenta. It becomes a problem at birth, which is one of the major points of this discussion.

You apparently have a much different definition of the word “reorganization” than I do.

Except when they don’t!

Again, the problem is not with these things all miraculously happening, but the fact that quite commonly they fail to happen.

Vanderzyden's conclusion is a gross non-sequitur:

Tell me Vanderzyden, when it comes time for your wife to give birth, do you think you will stand between her and her doctors with such pitiful defiance, because you know that the process of birth is so optimally designed that she and her baby need not worry about any potential problems during childbirth?

[ October 17, 2002: Message edited by: MrDarwin ]</p>

Dr Rick

MrDarwin's intelligently designed fetal blood flow would be an improvement over the evolutionary one that humans are stuck with, and for precisely the reasons he gave as it would obviate the need for either a ductus arteriosus or foramen ovale. MrDarwin's concept would work even if the the umbilical artery attached to the thoracic systemic vasculature instead of the pulmonary arteries as the lungs receive blood not only via the pulmonary arteries but also the systemic bronchial arteries. In other words, there are several potential design possibilities that would be an improvement over the unintelligent one we now have.

Rick