Final answer:
Cholecystokinin (CCK) is the hormone responsible for causing the gallbladder to contract and for prompting the liver to increase bile production. The secretion of this hormone is stimulated by the presence of fat in the duodenum. Bile is essential for the digestion of fats and is released from the gallbladder upon CCK's signal.
Step-by-step explanation:
The hormone that causes the gallbladder to contract and the liver to increase its production of bile is known as cholecystokinin (CCK). When fatty chyme enters the duodenum, the presence of fat triggers the secretion of CCK. This hormone not only causes the gallbladder to release bile into the duodenum by contracting but also stimulates the production of pancreatic lipase from the pancreas.
Besides CCK, another hormone called secretin also plays a role in bile production. While secretin primarily stimulates the pancreas to produce an alkaline bicarbonate solution, it acts in tandem with CCK to regulate the digestive secretions. Hepatocytes (liver cells) continuously produce bile, but the secretion increases in response to the hormonal signals when food, especially fatty food, is consumed.
Bile is crucial in the digestion process as it helps break down fats. The gallbladder concentrates and stores the bile produced by liver cells, conserving it between meals. When the gallbladder contracts, it sends bile through ducts into the duodenum to mix with the incoming fats, facilitating their digestion.