Can I upgrade the Graphics card in my iMac?

Looking at the photos posted for the iMac Intel 27" EMC 2309 and 2374 tear down it seems to be negatron on replacing or upgrading the graphics card. The graphics card and its memory are integrated into the motherboard. No doubt as a necessary consequence of the streamlined and thin design. No graphics card attached to a slot with its own fan and heat sync, just a chip on the board, flanked by RAM. All looks pretty permanent. Of course, anything is possible, but it would require skills and knowledge probably greater than building it all yourself. The makers of the first dye on chip designs used sewing machines, pressure cookers and even sunlight for exposure to miniaturize circuit designs so my faith in human ingenuity is not easily fluttered, but it would simply be easier to buy a new computer. This is Apple's primary objective. Just as ingenious as the technology, a marketing model that keeps the company in business. The upside is that there will be an Apple, Inc. ten years from now, most likely. I have to admire it as self-preservation as opposed to loathing it for its apparent greed. If that element wasn't pervasive then we wouldn't be here talking about it. We would perhaps all be on great plastic computers, typing crap, oblivious to so many possibilities in the alternate universe where Apple had significant profits from its oligarchy.