Secretin

Definition

Secretin is a hormone produced by the S cells in the small intestine that plays a crucial role in regulating digestive processes. It is released into the bloodstream in response to the presence of acidic chyme from the stomach, signaling the pancreas to secrete bicarbonate-rich fluid to neutralize the acidity and promoting bile secretion from the liver. This hormonal regulation ensures that the digestive environment is optimal for nutrient absorption.

5 Must Know Facts For Your Next Test

1. Secretin was first discovered in 1902 by British physiologist William Bayliss and Ernest Starling.
2. The main function of secretin is to stimulate the pancreas to release bicarbonate, which neutralizes gastric acid in the small intestine.
3. In addition to its role in regulating pH, secretin also promotes bile production and release from the liver.
4. Secretin's release is triggered primarily by acidic chyme entering the small intestine, but it can also be stimulated by fatty acids and certain amino acids.
5. It plays a vital part in maintaining homeostasis within the digestive system by ensuring an optimal environment for enzyme activity.

Review Questions

• How does secretin contribute to the digestive process after food leaves the stomach?
  • After food leaves the stomach as acidic chyme, secretin is released from S cells in the small intestine. This hormone signals the pancreas to release bicarbonate-rich fluid, which neutralizes the acidity of the chyme, creating a more suitable environment for enzymes to function effectively. Additionally, secretin stimulates bile production in the liver, further aiding in fat digestion and nutrient absorption.
• Discuss how secretin interacts with other hormones in the digestive system to regulate digestion.
  • Secretin works alongside other hormones such as cholecystokinin (CCK) and gastrin to ensure efficient digestion. While secretin primarily focuses on neutralizing stomach acid and promoting bile production, CCK is released in response to fats and proteins and stimulates gallbladder contraction for bile release and pancreatic enzyme secretion. This coordinated hormonal response optimizes digestion and nutrient absorption as food progresses through the digestive tract.
• Evaluate the importance of secretin in maintaining digestive homeostasis and what could happen if its function is disrupted.
  • Secretin plays a vital role in maintaining digestive homeostasis by ensuring that the pH level in the small intestine remains optimal for enzyme activity. If secretin's function is disrupted, it could lead to an inadequate release of bicarbonate, resulting in overly acidic conditions that hinder digestion and nutrient absorption. This disruption could also affect bile production, leading to impaired fat digestion, which may contribute to various digestive disorders or nutrient deficiencies over time.

Related terms

Pancreas: An organ that produces digestive enzymes and hormones, including insulin and glucagon, which are essential for regulating blood sugar levels.

Bile: A digestive fluid produced by the liver that helps emulsify fats, making them easier to digest and absorb in the small intestine.

Chyme: The semi-fluid mass of partly digested food that is expelled from the stomach into the small intestine.