How is bile regulated during digestion?

Bile production and release during digestion is regulated by hormones such as cholecystokinin and secretin.

Bile, a digestive fluid produced by the liver and stored in the gallbladder, plays a crucial role in the digestion and absorption of fats. Its production and release are finely tuned processes regulated by the body's hormonal system. When food, particularly fatty food, enters the stomach and then the small intestine, the presence of fat triggers the release of a hormone called cholecystokinin (CCK) from the cells of the intestine.

Cholecystokinin has two main effects. Firstly, it stimulates the gallbladder to contract, which results in the release of stored bile into the small intestine. Secondly, it signals the sphincter of Oddi, a muscular valve that controls the flow of digestive juices (including bile) to the small intestine, to relax. This allows bile to flow into the small intestine where it can emulsify fats, breaking them down into smaller droplets that can be more easily digested by enzymes.

Another hormone involved in bile regulation is secretin. Secretin is released in response to the acidic contents arriving in the small intestine from the stomach. It stimulates the liver to produce more bile and also signals the pancreas to release bicarbonate, which neutralises the stomach acid. This ensures that the environment in the small intestine is optimal for the action of digestive enzymes and bile.

In summary, the regulation of bile during digestion is a complex process involving the coordinated action of hormones, primarily cholecystokinin and secretin. These hormones respond to the presence of food in the digestive tract and ensure that bile is released at the right time and in the right quantities to facilitate efficient digestion and absorption of fats.