Your blood system is pressurized so you get circulation even through fine vessels and capillaries, it doesn’t depend on gravity. Blood flow works if you hang upside down. There are a few differences, pressure is higher at the feet than at the head by the height of a water column five to six feet high, say 3 psi. That difference won’t exist in zero-G. You won’t need the one-way valves in the leg veins to stop backwards flow under gravity.
Swallowing and digestion are propelled by muscular contractions, as is voiding solid waste, muscles also pressurise the bladder so those would happen equally well.
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