What effect does CCK have on the sphincter controlling the bile duct during digestion?

• A. It causes contraction of the sphincter
• B. It causes relaxation of the sphincter
• C. It has no effect on the sphincter
• D. It only affects gallbladder contraction

Answer: (B)

Cholecystokinin (CCK) is a hormone released by the small intestine in response to fatty acids and amino acids. Its primary role during digestion is to facilitate the digestion and absorption of fats and proteins. One of its key effects is on the sphincter of Oddi, which controls the flow of bile from the gallbladder and pancreas into the duodenum.

CCK induces relaxation of the sphincter of Oddi, allowing bile and pancreatic secretions to flow into the small intestine where they can aid in digestion. This is crucial because when the sphincter relaxes, it enables the contents of the gallbladder, which is stimulated by CCK to contract, to enter the digestive tract. By promoting this relaxation, CCK plays an essential role in coordinating the digestive process, ensuring that bile is available to help emulsify fats in the digestive tract at the right time.

Thus, recognizing that CCK's action leads to the relaxation of the sphincter helps to understand its overall role in digestive physiology, particularly in the context of fat digestion. The pathway here emphasizes the importance of hormonal regulation in coordinating digestive events and managing the flow of digestive juices effectively.