Function and Purpose of Secretin

Andria Emerson, Amanda Robb
  • Author
    Andria Emerson

    Andria Emerson has taught high school science for over 17 years. She has a M.S from Grand Canyon University in Educational Leadership and Administration, M.S from Grand Canyon University in Adult Education and Distance Learning, and a B.S from the University of Arizona in Molecular and Cellular Biology.

  • Instructor
    Amanda Robb

    Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

Learn to define what secretin is. Discover how the hormone secretin functions and where it is produced. Find out how secretin helps in digestion and water balance. Updated: 06/29/2022

Table of Contents


What is Secretin?

Secretin was the first hormone to be discovered in the early 1900s. A hormone is a substance that acts like a messenger providing chemical signals to different parts of the body. Hormones are released into the bloodstream where they interact with target cells to communicate messages and signal biochemical pathways to occur. Secretin is a hormone found in most mammals that regulates digestion and water balance in the body. Digestion is the process of breaking down food via enzymes and mechanical means into substances the organism can use.

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  • 0:02 What Is Secretin?
  • 0:45 Secretin and the…
  • 1:43 Secretin and Water Balance
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Where is Secretin Produced?

Secretin is produced by specialized cells called S cells found in the duodenum. The duodenum connects to the stomach and is the first part of the small intestine. The role of the duodenum is to absorb nutrients such as vitamins, minerals, carbohydrates, fats, proteins, and water. When pH levels in the duodenum become low, secretin is released. pH is a measure of the acidity or basicity of a substance. Acids have a pH below 7 and bases have a pH above 7.

The digestive system involves the duodenum which is the first part of the large intestines connected to the stomach.

Image showing duodenum connected to stomach

Secretin Function

What does secretin do? Secretin has many different functions, however, its main roles are to stimulate the pancreas to secrete pancreatic juices, regulate the pH in the small intestines, and regulate water balance in cells.

Secretin regulates pH by influencing gastric acid and bicarbonate release. Gastrin is a digestive hormone that triggers the release of gastric juices such as hydrochloric acid. Gastric juices break down matter in food and kill bacteria. When gastric juices are present, prosecretin, a precursor to secretin, is activated becoming secretin. Gastric juices such as hydrochloric acid have a pH of 3.5 and are very acidic. As hydrochloric acid passes from the stomach to the duodenum, secretin is released into the bloodstream. This stimulates duct cells of the pancreas to secrete water and bicarbonate. Bicarbonate is a byproduct of the body's metabolism and is regulated by the kidneys. Bicarbonate acts as a base to neutralize acids. Water and bicarbonate work to neutralize the acidic hydrochloric acid secreted by the stomach preventing damage to the lining of the small intestine.

Secretin plays a role in maintaining water balance or osmolality in cells. The concentration of water in cells is strictly regulated in order to prevent cells from swelling or contracting. Cells that are too large or too small to not function properly can become damaged and die. In order to control osmolality, water intake and excretion by cells must be regulated. When water levels are low, cells in the hypothalamus located in the brain release vasopressin which causes the kidney to increase water reabsorption. Vasopressin is a hormone produced by the body that signals the kidneys to reduce urine flow and retain water. Secretin and vasopressin both play a role in maintaining water balance.

How Does the Hormone Secretin Help in Digestion?

Secretin aids in digestion by stimulating the pancreas to make pancreatic fluids. The pancreas is a gland that secretes enzymes into the duodenum necessary for digestion. The pancreas also contains specialized cells that regulate blood sugar. Pancreatic juices are usually alkaline or more basic and break down sugars, fats, and starches. As pH levels drop from gastric juices, secretin is stimulated. This in return stimulates cells in the pancreas to produce bicarbonate. The bicarbonate combines with the acidic gastric juices neutralizing the environment and bringing the pH back to normal levels.

How Does Secretin Regulate Water Balance?

Secretin plays a role in regulating water balance by acting on the hypothalamus, pituitary gland, and kidneys. When water levels in the body are low, secretin is released by cells in the hypothalamus found in the brain. This causes vasopressin to be released.

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Frequently Asked Questions

What stimulates release of secretin?

Secretin is stimulated by gastric acids that cause the pH in the duodenum to become more acidic. Secretin is also utilized in connection with vasopressin to maintain water balance in cells.

What is the function of secretin?

Secretin has three main roles:

1. Stimulate the pancreas to secrete pancreatic juices

2. Regulate the pH in the small intestines

3. Regulate water balance in cells

What is the role of secretin in the digestion process?

Secretin stimulates the pancreas to make pancreatic fluids. Pancreatic fluids contain bicarbonate which helps to neutralize stomach acids. This causes the environment of the intestine to be less acidic.

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