How Do Spiders Make Venom?

It 's an age old question and I'm sure you'd like an answer, well here goes:

Spiders have a pair of venom-producing glands behind their mouthparts. Venom (some times incorrectly called poison) from each gland passes down a tube which takes it to the opening at the end of each of the pair of fangs where it is ejected when the spider bites.

In most cases this venom is used to disable the spiders prey, it also is used to liquidise the insides of the prey so that the spider can suck up the soup-like mixture.

The venom is made of of various chemicals that in many cases interfere with mobility and even the ability of the brain and nervous system to function correctly in the envenomated (bitten) victim.