Secretin is secreted by the?

DHS Staff Nurse - 2018 (Shift-2nd)

Applied Physiology

Easy

Appeared in: DHS Staff Nurse - 2018 (Shift-2nd)

Explanation

Secretin is a key gastrointestinal hormone responsible for regulating the pH in the small intestine.
It is produced and secreted by specialized endocrine cells called 'S cells'.
These S cells are most abundant in the mucosa of the duodenum, the first section of the small intestine.
The release of secretin is triggered when acidic chyme (partially digested food from the stomach) enters the duodenum.
Its primary function is to stimulate the pancreas to release a bicarbonate-rich fluid, which neutralizes the acid and protects the intestinal lining.

Option A: The pancreas is the primary target organ for secretin, but it does not secrete it. Secretin stimulates the pancreas to release bicarbonate and water.
Option C: The liver is a target for secretin, which stimulates it to produce more bile. However, the liver's primary endocrine functions relate to other hormones and proteins, not secretin secretion.
Option D: The kidney is an organ of the urinary system and is not involved in the secretion of secretin. Its endocrine functions include secreting hormones like erythropoietin (for red blood cell production) and renin (for blood pressure regulation).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Source of Secretin Hormone Secretion as background academic context rather than a clinical decision trigger.
Understanding the function of secretin is crucial for diagnosing pancreatic disorders. A 'secretin stimulation test' can be performed where synthetic secretin is administered to a patient, and the pancreatic fluid is collected to measure bicarbonate output. A low output can indicate exocrine pancreatic insufficiency, a condition seen in chronic pancreatitis or cystic fibrosis.
In conditions like Zollinger-Ellison syndrome, where a gastrin-producing tumor causes excessive stomach acid, the body's secretin response is also affected, which can be a diagnostic clue.
What if? If a patient had a damaged duodenal lining (e.g., from severe celiac disease), the ability to secrete secretin would be impaired. This would lead to insufficient neutralization of stomach acid, potentially causing duodenal ulcers and maldigestion due to pancreatic enzymes not functioning at the correct pH.

How to Approach the Question

First, identify the core subject of the question, which is the origin of the hormone 'secretin'.
This is a factual recall question from physiology, specifically the endocrine functions of the gastrointestinal tract.
Mentally review the major GI hormones (Gastrin, Secretin, CCK) and their primary sites of secretion.
Recall that Gastrin is from the stomach (G cells), and Secretin and CCK are from the upper small intestine (duodenum/jejunum).
Specifically, remember that Secretin is secreted by S cells in the duodenum in response to acid.
Evaluate the options: Pancreas and Liver are targets of secretin, not sources. Kidney is unrelated to this digestive process. This leaves the Duodenum as the correct source.

Concept Tested & Keywords

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