--- title: "Cholecystokinin (CCK) | Anatomy and Physiology I" description: "Cholecystokinin (CCK) is a small-intestine hormone that triggers bile release and pancreatic enzymes, then slows stomach emptying in Anatomy and Physiology I." canonical: "https://fiveable.me/anatomy-physiology/key-terms/cholecystokinin-cck" type: "key-term" subject: "Anatomy and Physiology I" unit: "Unit 17" --- # Cholecystokinin (CCK) | Anatomy and Physiology I ## Definition Cholecystokinin (CCK) is a hormone released by the small intestine when fats and proteins enter it. In Anatomy and Physiology I, it signals the gallbladder and pancreas to support digestion and slows gastric emptying. ## What It Is Cholecystokinin, or CCK, is a digestive hormone released by the small intestine, mainly the duodenum and jejunum, when fatty acids and partially digested proteins enter the lumen. In Anatomy and Physiology I, you usually meet it as one of the body’s chemical signals that coordinates digestion after a meal. CCK is made by enteroendocrine cells in the intestinal lining. These cells do not make digestive enzymes themselves. Instead, they sense what is arriving from the stomach and then release a hormone into the bloodstream to tell other organs what to do next. Its biggest job is to match digestion to food type. When CCK rises, it tells the gallbladder to contract and release bile into the small intestine. Bile does not break fats apart chemically, but it emulsifies them, which makes them easier for lipase and other enzymes to work on. CCK also stimulates the pancreas to release digestive enzymes, especially those needed for fat and protein digestion. CCK also slows gastric emptying. That means the stomach releases chyme into the small intestine more gradually. This gives the small intestine time to handle the incoming fats and proteins instead of being flooded with more material than it can process. A good way to think about CCK is as a coordination hormone. The stomach starts digestion, but CCK helps shift the workload to the small intestine and accessory organs. Without that signal, fat digestion would be less efficient and the timing of digestion would be off. You may also see CCK mentioned in the context of satiety, or the feeling of fullness. That is because digestive hormones do more than move food through the GI tract. They also help the body regulate how much more food you are likely to eat after a meal. ## Why It Matters CCK shows how digestion is regulated, not just how food moves. In Anatomy and Physiology I, that matters because the digestive system is usually taught as a chain of organs, but the real process depends on hormone signaling, feedback, and coordination between the gut and accessory organs. This term connects the stomach, liver, gallbladder, and pancreas into one working system. If you know what CCK does, you can explain why the gallbladder empties after a fatty meal, why pancreatic enzymes get released into the small intestine, and why the stomach does not dump chyme all at once. It also shows the difference between mechanical, chemical, and hormonal control. CCK does not digest food directly. Instead, it tells other structures to release the substances that do the chemical work. That distinction comes up a lot when you are comparing digestive processes or tracing what happens after nutrients enter the duodenum. When you see a question about fat digestion, CCK is often part of the answer because bile and pancreatic enzymes are both involved. It is one of the clearest examples of how the endocrine system supports another body system without being the main focus of the chapter. ## Connections ### Gallbladder CCK causes the gallbladder to contract and release bile into the small intestine. If you are tracing the path of fat digestion, the gallbladder is the storage site, and CCK is the signal that tells it to empty after a meal with fats. ### [Pancreatic enzymes](/anatomy-physiology/key-terms/pancreatic-enzymes) CCK stimulates the pancreas to release enzymes that digest fats, proteins, and other nutrients in the small intestine. This is the part of the process that turns hormone signaling into actual chemical digestion, especially in the duodenum. ### [Bile Production](/anatomy-physiology/key-terms/bile-production) Bile production happens in the liver, but CCK helps the body use that bile at the right time by triggering gallbladder release. That makes this term useful when you are separating where bile is made from where it is stored and released. ### Lipid metabolism CCK is closely tied to lipid metabolism because fats in the small intestine are one of the main triggers for its release. When you see a meal rich in lipids, CCK is part of the reason bile and pancreatic enzymes are brought into action. ## On the AP Exam A quiz item may ask you to match CCK with the organ it targets, or to explain what happens when fatty chyme enters the duodenum. In a diagram question, you might trace the sequence from small-intestine sensing to gallbladder contraction, pancreatic enzyme release, and slower gastric emptying. On short-answer problems, the best move is to describe the trigger first, then the response. If you get a case about a fatty meal, mention CCK as the hormone that coordinates bile and enzyme delivery. If the question asks why stomach emptying slows, CCK is usually part of that explanation too. The key is to connect the hormone to the function, not just name it. ## Key Takeaways - Cholecystokinin (CCK) is a hormone released by the small intestine when fats and proteins enter it. - CCK tells the gallbladder to contract and release bile, which helps emulsify fats for digestion. - It also stimulates the pancreas to release digestive enzymes into the small intestine. - CCK slows gastric emptying, so chyme moves out of the stomach at a pace the small intestine can handle. - This hormone is a good example of how the digestive and endocrine systems work together. ## FAQs ### What is cholecystokinin (CCK) in Anatomy and Physiology I? CCK is a digestive hormone released by the small intestine, especially when fats and proteins enter the duodenum. It signals the gallbladder and pancreas to support digestion and helps slow the stomach so digestion can happen in an orderly way. ### What stimulates the release of CCK? Fats are the strongest trigger, and proteins also stimulate its release. When partially digested nutrients reach the small intestine, enteroendocrine cells detect them and release CCK into the blood. ### How does CCK help digest fats? CCK makes the gallbladder contract so bile enters the small intestine, where it emulsifies fat into smaller droplets. It also stimulates pancreatic enzyme release, which supports further fat digestion. ### Is CCK the same as a digestive enzyme? No. CCK is a hormone, not an enzyme. It does not break food down directly, but it tells other organs to release bile and enzymes that do the digestive work. ## Related Study Guides - [17.10 Organs with Secondary Endocrine Functions ](/anatomy-physiology/unit-17/organs-secondary-endocrine-functions/study-guide/5SR4qT8SbPFoWPuD) - [23.6 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder ](/anatomy-physiology/unit-23/6-accessory-organs-digestion-liver-pancreas-gallbladder/study-guide/CgJYPpHvj8xQTkLI) - [23.1 Overview of the Digestive System ](/anatomy-physiology/unit-23/1-overview-digestive-system/study-guide/YrHMDXNIFoqC4F3W) - [23.4 The Stomach ](/anatomy-physiology/unit-23/4-stomach/study-guide/rKTnfF5NUTOqfZzY) - [23.2 Digestive System Processes and Regulation ](/anatomy-physiology/unit-23/2-digestive-system-processes-regulation/study-guide/zgKyu8g4N3X9pFf5) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/anatomy-physiology/key-terms/cholecystokinin-cck#resource","name":"Cholecystokinin (CCK) | Anatomy and Physiology I","url":"https://fiveable.me/anatomy-physiology/key-terms/cholecystokinin-cck","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology/key-terms/cholecystokinin-cck#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:20:38.182Z","isPartOf":{"@type":"Collection","name":"Anatomy and Physiology I Key Terms","url":"https://fiveable.me/anatomy-physiology/key-terms"},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/anatomy-physiology/key-terms/cholecystokinin-cck#term","name":"cholecystokinin (CCK)","description":"Cholecystokinin (CCK) is a hormone released by the small intestine when fats and proteins enter it. 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