To recap: Parker is bit by the radioactive spider that is also a genetic hybrid of three different breeds of spider, one of which happens to be an excellent and prolific web-spinner. The venom, or some DNA from the spider's saliva, or something starts to do a number on Parker and his immune system. He goes to bed with flu like symptoms(1).
During the night, fibroblasts and myoblasts(2) migrate to Parker's palms because he has been chronically abrading them from some unkown activity, which he may have been performing that night, despite his illness. The fibroblasts form a bursa in each palm, full of synovial fluid that is altered by the spider's venom, or DNA, so that it dehydrates quickly, is adhesive instead of slimy, and has incredible tensile qualities.
Myoblast (Looks a little like a fibroblast, doesn't it?)
Now, here is my more fanciful stretch of the imagination(3): myoblasts, found in the repairing injured tissue of Parker's inflamed palm, infuse and strengthen the structure of the bursa. Normally they would weaken or recede after repair is complete. These cells, thanks to the spider DNA, become incredibly strong smooth muscle cells, much like the cells that line one's intestine(4). Come to think of it, since Parker's skeletal muscle is transformed into incredibly strong tissue, it stands to reason that the smooth muscle in his gut (and everywhere else) is now super-strong as well.
Smooth muscle contracts with a wave-like actions known as peristalsis. This coordinated rippling in the gut gets your food through your digestive tract and excreted through your other end(5).
(The principle is the same)
WHERE'S THE HOLE?
Parker aims his wrist at a distant object, flexes his third and fourth fingers, pressing into his newly formed bursa as he hyperextends his wrist to increase pressure on the fluid deep within the new sac of palmar fascia. The smooth muscle around the bursa contracts with peristaltic Spidey-strength and propels a mighty stream of whitish sticky stuff out his... wait a minute...
My God!!! Parker has no hole! (In his wrist.) He has to have a hole there or nothing is going to come out. And how can Parker release a precise stream of fluid propelled for tens of yards on muscle power alone without a sphincter to control that mighty stream?
Only a scar
At his wrist we see a shot of a star-shaped scar-like structure, but there is no opening in his skin. there has to be a flap, or slit in the skin, or a miniature anus, or something. i understand that the producers might have felt that showing a puckered little sphincter or even a urethra-like opening on Parker's wrists might be a mood killer, but authenticity is important!
We're supposed to believe that these super-spider-DNA-enhanced-bursae with peristaltic sphincter propulsion just magically transport this sticky fluid through his palms and onto buildings without an opening in his skin? If there's no hole there, then how is any of this believable? My day has been ruined! Now I feel foolish analyzing this whole scenario, which obviously can't occur due to a simple lack of aperture!
Next, they'll be trying to get us to suspend disbelief as we watch some guy hook himself up to a robot with tentacles, that takes over his mind during a lab accident.
Speaking of robots, well robots and cyborgs, next time we will look at a few moments from the new Terminator movie.
1. For more about flu like symptoms you can see Spidey Palm 1 (5/04/09). For you trivia buffs, Star Trek also relies on flu like symptoms for a small bit of plot (5/10/09).
2. Myoblasts are the cells from which all three types of muscle tissue develops, in utero. A type of myoblast helps repair injured tissues in adults. The textbook Human Anatomy and Physiology by Marieb and Hoehn, 7th Edition, 2007 from Pearson Benjamin Cummins, pp. 316-317, has an interesting explanation of myoblasts and what they do.
3. As if the rest of this was "sound science."
4. There are three kinds of muscle tissue: cardiac, found in (you guessed it!) the heart; smooth, found in glands and tubular organs; and skeletal, attaching mostly to bone. This is the type of muscle we use to move around with, and we eat as steak.
5. Anus. There. I said it. You have an anus, as do I, as does Peter Parker, and Mary Jane Watson. Plural of anus can be either anuses or anii.