why doesn’t the digested food in the duodenum push itself into the bile and panceratic ducts?
While there may be other reasons, two to consider are:
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General peristalsis movement is away from the ducts, meaning the food would have to either be stagnant, or the intestines really full, or the movement be the opposite way (towards the stomach instead of towards the colon).
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The ducts are not just open holes, the opening to the intestines is smaller (in the ones I’ve seen in animals) than the ducts themselves. Also, they are positioned so that it is very hard for backflow to get in (see above).
Oh, and digested (or partially digested) food going up the ducts ducts is rare, but does happen (at least in some animals).
The common bile duct has a ring shaped muscle, the sphincter of Oddi, which only opens to allow fluids to travel into the duodenum.
You can think of all the connections in the digestive system as being one-way valves. The lower esophageal sphincter that lies between the esophagus and stomach is somewhat of an exception, since it allows some back passage, but that results in problems like vomiting and heartburn, so it is not the norm. It is part of the design to allow the body to purge harmful substances as quickly as possible but those should be rare. Beyond that, everything is designed to push food in one direction and serious problems would occur if any disruptions would breach the valves.
Pretty much the same thing that keeps water from entering your butt when you’re swimming.
My gallbladder is wearing a Speedo?
I thought that was the purpose of gallstones - to block the bile duct.
I kid, I kid.
Pancreatitis is no laughing matter. In fact, I think it’s probably the worst pain imaginable.