The hormones secretin and pancreozymin are secreted by:

DSSSB 13 August 2024

Applied Physiology

Easy

Appeared in: DSSSB 13 August 2024

Explanation

The duodenum, the first section of the small intestine, is the primary site for the secretion of secretin and pancreozymin (cholecystokinin/CCK).
Specialized endocrine cells in the duodenal lining, known as S-cells, release secretin when acidic chyme arrives from the stomach.
Other endocrine cells, called I-cells, release CCK in response to the presence of fats and proteins in the chyme.
These hormones are crucial for coordinating digestion by signaling the pancreas to release bicarbonate and enzymes, and the gallbladder to release bile.

Option A: While the jejunum (the middle section of the small intestine) does secrete small amounts of these hormones, the duodenum is the principal and most significant source due to its immediate proximity to the stomach.
Option C: The appendix is a small pouch attached to the large intestine. Its primary function is immunological, acting as a storehouse for beneficial gut bacteria, and it does not play a role in secreting digestive hormones.
Option D: The liver produces bile, which is essential for fat digestion. It is a target organ for hormones like secretin and CCK, but it does not secrete them. CCK stimulates the gallbladder (which stores bile from the liver) to contract.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of digestion in the upper gastrointestinal tract as background academic context rather than a clinical decision trigger.
Understanding the source and function of these hormones is vital for diagnosing and managing conditions like pancreatitis, gallstones, and peptic ulcer disease.
A secretin stimulation test can be used to assess pancreatic function and to help diagnose gastrinomas (Zollinger-Ellison syndrome), where gastrin levels are abnormally high.
What if? If a patient had a tumor blocking the pancreatic duct, digestive enzymes stimulated by CCK could not reach the duodenum. This would lead to malabsorption and autodigestion of the pancreas, causing acute pancreatitis, a medical emergency.

How to Approach the Question

Identify the key terms in the question: 'secretin' and 'pancreozymin'.
Recall or recognize that 'pancreozymin' is an alternative name for cholecystokinin (CCK).
Consider the physiological sequence of digestion. Food (chyme) passes from the stomach into the first part of the small intestine.
This initial segment must detect the chyme's composition (acid, fat, protein) and release hormones to trigger the next phase of digestion.
Identify the first part of the small intestine from the options provided, which is the duodenum.
Eliminate the other options based on their primary functions: Jejunum is further along the tract with a lesser role in this specific secretion, the appendix is a lymphoid organ, and the liver is a target organ, not the source of these hormones.

Concept Tested & Keywords

Concept Tested: Hormonal regulation of digestion in the upper gastrointestinal tract.
Stem keywords: hormones, secretin, pancreozymin, secreted by
Lead-in keywords: BEST, MOST RELEVANT CLUE
Negative lead-in flag: false

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E6 Physiology Ganong 27e Vol 2 Part 1 p. 14-16