The body, the almost perfect machine.

[Bobbin]

the appendix was suppose to grow out as a wing, but then natural selection decided...nah this is not gonna be beneficial for the creature, he's too heavy to fly.

You know if you just opened your eyes a bit...

Ah nevermind.

 

[porn$tar]

the appendix was suppose to grow out as a wing, but then natural selection decided...nah this is not gonna be beneficial for the creature, he's too heavy to fly.

I see natural selection has decided that you don't need a brain.

 

[porchrat]

Don't feed the trolls that come into the Natural Sciences section with anti-science.

 

[General P]

....so why do we have an appendix, tonsils and a foreskin - all of which are expendable ?

Apparently the appendix is part of the immune system.

The Grolier Encyclopedia admitted, "Long regarded as a vestigial organ with no function in the human body, the appendix is now thought to be one of the sites where immune responses are initiated."2 Authors Van De Graff and Fox state, "The appendix contains masses of lymphoid tissue that may serve to resist infection."3 Kenneth Saladin states, "The appendix is densely populated with lymphocytes [a type of white blood cell] and is a significant source of immune cells."4 Anatomist Fred Martini describes the appendix as saying, "The mucosa and submucosa of the appendix are dominated by lymphoid nodules, and the appendix's primary function is as an organ of the lymphatic system."5


_____________________________
1. Zuidema, G., Johns Hopkins Atlas of Human Functional Anatomy, 1980, p. 86.
2. Hartenstein, Roy, Grolier Encyclopedia, 2002, Grolier Interactive Inc.
3. Van De Graff & Fox, Concepts of Human Anatomy & Physiology, 1999, p. 837.
4. Saladin, K., Anatomy & Physiology, McGraw Hill, 2001, p. 974.
5. Martini, F., Fundamentals of Anatomy & Physiology, Prentice Hall, 1998, p. 899.

 

[General P]

Also, you forgot a few other 'imperfections'. Off the top of my head:
inside out eyes, with a blindspot (Octopus / squids have much better eyes than us, similar to ours, but with all the problems fixed)

Humans live in the air and air does not block uv light. We need the blood vessels in front of the retina because it serves as the last defense against uv light.

Octopus lives in water and water blocks uv light so they can have their blood vessels behind the retina which will give them better vision in the deep ocean than humans would have but humans don’t live in the deep ocean.

The human eye is perfectly suited for its environment. If it were like the octopus’ it would be damaged very fast by uv light.

 

[Jab]

Humans live in the air and air does not block uv light. We need the blood vessels in front of the retina because it serves as the last defense against uv light.

Octopus lives in water and water blocks uv light so they can have their blood vessels behind the retina which will give them better vision in the deep ocean than humans would have but humans don’t live in the deep ocean.

The human eye is perfectly suited for its environment. If it were like the octopus’ it would be damaged very fast by uv light.

Source?

 

[porchrat]

Apparently the appendix is part of the immune system.

The appendix is thought to be part of the lymphatic system. There is a difference.

The same story applies to the tonsils. Lymphatic tissue.

What we do know is that neither the appendix nor the tonsils are needed for a healthy life.

 

[General P]

Source?

There are two sources of blood supply to the mammalian retina: the central retinal artery and the choroidal blood vessels. The choroid receives the greatest blood flow (65-85%) (Henkind et al., 1979) and is vital for the maintainance of the outer retina (particularly the photoreceptors) and the remaining 20-30% flows to the retina through the central retinal artery from the optic nerve head to nourish the inner retinal layers. The central retinal artery has 4 main branches in the human retina (Fig. 17).

http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/

So, the blood vessels on the front surface of the retina avoid areas where acute vision is essential and may instead supply nutrients via diffusion into the vitreous humour. The blood vessels could also serve a second purpose, as blood vessels have important roles in repair. It is possible that they can grow out across the retina in response to damage, bringing white blood cells to the place of damage and taking away debris, and then retract later when damage has been repaired.

http://www.catalase.com/retina.htm

The human body has built-in protective devices to prevent damage to delicate retinal tissue. While they are not fully effective against all UVR, they do provide a certain level of defense. Eyebrows and eyelids act as screens from damaging rays. Squinting and the constriction of the pupil are automatic reflexes that also protect. The cornea itself acts as a filter; it absorbs 100% of UV-C. The anterior layers of the cornea absorb much of the UV-B that we are exposed to. The crystalline lens absorbs most UVR up to 370nm; that is the balance of the UV-B that is not absorbed by the cornea, as well as most of the UV-A. The aqueous and vitreous humours may also absorb a small amount of UVR.

http://www.opto.ca/oa/online_ce.html

 

[porchrat]

http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/



http://www.catalase.com/retina.htm


http://www.opto.ca/oa/online_ce.html

Ummm... no offence but nothing there says that the vessels serve as a defence against UV light.

I'm interested to see where you got that information from considering in all the time I've ever spent studying the eye I've never once heard that claim.

 

[General P]

The appendix is thought to be part of the lymphatic system. There is a difference.

The same story applies to the tonsils. Lymphatic tissue.

What we do know is that neither the appendix nor the tonsils are needed for a healthy life.

The appendix plays a role in antibody production, protects part of the intestine from infections and tumor growths (c), and safely stores “good bacteria” that can replenish the intestines following bouts of diarrhea, for example (d). Indeed, the absence of true vestigial organs implies evolution never happened.

“The appendix is not generally credited with substantial function. However, current evidence tends to involve it in the immunologic mechanism.” Gordon McHardy, “The Appendix,” Gastroenterology, Vol. 4, editor J. Edward Berk (Philadelphia: W. B. Saunders Co., 1985), p. 2609.


“Thus, although scientists have long discounted the human appendix as a vestigial organ, a growing quantity of evidence indicates that the appendix does in fact have a significant function as a part of the body’s immune system.” N. Roberts, “Does the Appendix Serve a Purpose in Any Animal?” Scientific American, Vol. 285, November 2001, p. 96.


“...the human appendix is well suited as a ‘safe house’ for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal track are purged following exposure to a pathogen....the appendix...is not a vestige.” R. Randal Bollinger et. al., “Biofilms in the Large Bowel Suggest an Apparent Function of the Human Vermiform Appendix,” Journal of Theoretical Biology, Vol. 249, 2007, p. 826.

http://www.voy.com/208012/2/373.html

It's true, one can live without the appendix. Probably if it is infected and may need to be taken out, but I don't think it's safe to say we don't need it. As much as a kidney may get infected and one may need to be removed but it does not mean one has no use. Just like hands or legs; a person can live without them, but we can't say he doesn't need them.

 

[porchrat]

http://www.voy.com/208012/2/373.html

It's true, one can live without the appendix. Probably if it is infected and may need to be taken out, but I don't think it's safe to say we don't need it.

If you can live a normal perfectly healthy life then yes it is safe to say we don't need it for a normal healthy life. If you needed it and it was removed you would not live a perfectly normal healthy life. Duh.

As much as a kidney may get infected and one may need to be removed but it does not mean one has no use.

When you remove a kidney you can't live a normal healthy life. There are conditions to the way you live. You must after that take care of yourself. Not so when you have your appendix removed. When you have your appendix removed you need not change your life in any way. You just go on living the way you always have with no detrimental effects.

If the appendix plays a part in your immune system it plays an exceptionally minor one that you can easily do without as evidenced by the millions of people that have had their appendix removed and live perfectly normal lives without them.

Just like hands or legs; a person can live without them, but we can't say he doesn't need them.

Again not comparable. If your hand or leg was removed your life would not be as it was.

Please read and comprehend what I'm saying before you respond with stuff like this. It is almost not worth my time to bother to respond to it.

AND BY THE POWER OF GREYSKULL I JUST WENT TO THAT LINK! Stop reading that crap it is going to rot your brain. It will turn you into one of those anti-science creationist yahoos.

 

[Jab]

Ummm... no offence but nothing there says that the vessels serve as a defence against UV light.

I'm interested to see where you got that information from considering in all the time I've ever spent studying the eye I've never once heard that claim.

Yes, if the blood vessels are in any way effective in blocking UV light, it would also be effective in blocking visible light.

 

[General P]

Ummm... no offence but nothing there says that the vessels serve as a defence against UV light.

I'm interested to see where you got that information from considering in all the time I've ever spent studying the eye I've never once heard that claim.

But given that about 1% of UV-A reaches the retina in the normal eye (and we know it is bad for the eye) and we know that these blood vessels maintain the retina and also respond to damage; is it incorrect to say we need these blood vessel for protection (or maintenance/defense)? Is it not logical to conclude that given their maintenance function the retina would be damaged quickly if they were absent?

 

[tcofran]

Three freshman engineering students were sitting around talking between classes, when one brought up the question of who designed the human body.

One of the students insisted that the human body must have been designed by an electrical engineer because of the perfection of the nerves and synapses.

Another disagreed, and exclaimed that it had to have been a mechanical engineer who designed the human body. The system of levers and pullies is ingeniuos.

"No," the third student said "your both wrong. The human body was designed by an architect. Who else but an architect would have put a toxic waste line through a recreation area?"

 

[porchrat]

But given that about 1% of UV-A reaches the retina in the normal eye (and we know it is bad for the eye) and we know that these blood vessels maintain the retina and also respond to damage; is it incorrect to say we need these blood vessel for protection (or maintenance/defense)? Is it not logical to conclude that given their maintenance function the retina would be damaged quickly if they were absent?

Of course it is logical to conclude that we need blood vessels for maintenance. All your cells need blood for maintenance not just those of the retina. Without a blood supply your retina would be completely dead not just damaged. However that isn't what you assumed, you assumed they block UV light. That is the illogical part. There is nothing I've ever read to suggest that they would be there to block UV light. From what I know about the nature of UV light it is silly to suggest that blood vessels could perform this function. UV light won't be stopped by fine capillaries. Heck UV light isn't even completely stopped by the cornea and that is one massive crystalline shield many many many many many many times thicker and denser than mere capillaries.

Furthermore the blood vessels don't need to be above the retina to perform their function. They could just as easily be beneath the photoreceptors. Unfortunately for us it wasn't detrimental enough to be eliminated through natural selection out so we're stuck with rubbish eyes. All the blood vessels being above the retina are is a major fail in the eye.

 

[General P]

Of course it is logical to conclude that we need blood vessels for maintenance. All your cells need blood for maintenance not just those of the retina. Without a blood supply your retina would be completely dead not just damaged. However that isn't what you assumed, you assumed they block UV light. That is the illogical part. There is nothing I've ever read to suggest that they would be there to block UV light. From what I know about the nature of UV light it is silly to suggest that blood vessels could perform this function. UV light won't be stopped by fine capillaries. Heck UV light isn't even completely stopped by the cornea and that is one massive crystalline shield many many many many many many times thicker and denser than mere capillaries.

Furthermore the blood vessels don't need to be above the retina to perform their function. They could just as easily be beneath the photoreceptors. Unfortunately for us it wasn't detrimental enough to be eliminated through natural selection out so we're stuck with rubbish eyes. All the blood vessels being above the retina are is a major fail in the eye.

You are one of the brilliant minds in this forum and I got respect for you.

But if you look at my statement it does not say blood vessels block uv light. I only spoke of defense and you assumed that I meant blocking out uv light. It is not unreasonable to say maintenance, damage control / limitation / repairs are some forms of defensive actions.

So I think as far as us having “rubbish eyes” we must agree to disagree.

 

[porchrat]

You are one of the brilliant minds in this forum and I got respect for you.

Thank you for the compliment but I don't consider myself one of the brilliant minds on this forum.

But if you look at my statement it does not say blood vessels block uv light. I only spoke of defense and you assumed that I meant blocking out uv light. It is not unreasonable to say maintenance, damage control / limitation / repairs are some forms of defensive actions.

You are right. You didn't actually say the blood vessels block UV light. I apologise for assuming that. That was the only conclusion I could draw from what I read based on what I know about physiology but I realise that while it seemed perfectly logical to me it isn't what you meant because you don't necessarily have the level of understanding I have. Nothing wrong with that. Not everyone takes physiology at university. It is after all a largely useless subject anyway

So I will have to explain myself more fully:

You say we have the vessels above the photoreceptors in order to perform maintenance operations. While I agree that blood supplies are there to perform maintenance operations they most definitely do not need to be above the photoreceptors to perform this function. Think about your skin. It has an adequate blood supply but the blood vessels are not above your skin, they're below stretching upwards into your skin. This is how a more efficient human eye would be. With the blood vessels below with fine capillaries working their way upwards into the retinal tissue to nourish the cells and remove waste. See what matters is not whether the blood vessels are above or below the tissue being supplied but how closely networked the vessels are with the tissues. Normally there is no cell in your body that is more than about 1mm away from some or other blood vessel. That is how closely networked everything is. That doesn't mean though that blood vessels sitting on top of the photoreceptors blocking portions of visible light are a good thing to help us see better or even maintain the eye in the long run. They aren't. There is no positive benefit that I know of to having the blood vessels above the retinal tissue, only negatives.

So hopefully after reading that you can understand (not excuse) my leaping to a conclusion about you thinking blood vessels above the eye would block UV light. I dismissed the idea that you thought they were nourishing the tissue and that that was the only way that they could do it because from what I know about physiology that is a stupid way to nourish tissue that needs to receive light.

So I think as far as us having “rubbish eyes” we must agree to disagree.

Not really no. Only if you're not prepared to learn a little about physiology.

 

[Jab]

But if you look at my statement it does not say blood vessels block uv light. I only spoke of defense and you assumed that I meant blocking out uv light. It is not unreasonable to say maintenance, damage control / limitation / repairs are some forms of defensive actions.

You claimed the blood vessels were "the last defense against uv light" and "If it were like the octopus’ it would be damaged very fast by uv light". Nothing in the sources you quoted supported your claim.

 

[General P]

You claimed the blood vessels were "the last defense against uv light" and "If it were like the octopus’ it would be damaged very fast by uv light". Nothing in the sources you quoted supported your claim.

...already been through this with porchrat...

 

[porchrat]

...already been through this with porchrat...

Not really. Your claim still isn't supported. All you clarified was that you won't claiming that they block UV light. Even taken to mean that you were just referring to the vessels and their capacity to nourish the retina your claim is still bullschit.