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Post by Lynn » Fri Jun 02, 2006 6:16 pm

I know the general fucntion of spiracles in grasshoppers, (they are respiratory organs leading to the tracheae) but my biology 11 teacher has me stumped: Are there inhalatory and exhalatory spiracles and if so, how many of each?

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Post by Darby » Fri Jun 02, 2006 8:58 pm

As far as I can remember, air goes in and out through each spiracle. Each spiracle is connected to one area of inner tissues

I also seem to recall that "inhale" and "exhale" doesn't always apply to tracheal systems. Some high-metabolism insects have specific abdomen-contracting muscles to squeeze air out of the system, but many don't have a dedicated pump.

Often, too, the systems aren't actually full of air - they're only as filled as the current oxygen needs dictate. The innermost tubes have tissue fluid in them, which actually reduces water loss to the atmosphere.

I have no idea if the tracheal linings have smooth muscle that might also help to empty the system, which would refill when the muscles relax - it makes sense that there would be, though.

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Post by MrMistery » Sat Jun 03, 2006 10:57 am

No the tracheal lining does not have smooth muscles. Expiration is active in arthropods with this kind of breathing, but it is done by other muscles. Contrary to lung vertebrates, inspiration is passive.
I agree, there are no inhalatory and exhalatory spiracles, just as you have only one trachea, you don't have one for inhaling and one for exhaling ;)
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

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