Duodenum

Definition

The duodenum is the first section of the small intestine, connecting the stomach to the jejunum. It plays a crucial role in the digestive process by receiving partially digested food, bile from the liver, and pancreatic juices that contain digestive enzymes. This part of the intestine is essential for nutrient absorption and further digestion.

5 Must Know Facts For Your Next Test

1. The duodenum is approximately 25-30 centimeters long and is shaped like a 'C' around the head of the pancreas.
2. It is divided into four segments: superior, descending, horizontal, and ascending duodenum.
3. The mucosal lining of the duodenum contains specialized cells that secrete hormones such as secretin and cholecystokinin, which regulate digestive processes.
4. Most chemical digestion occurs in the duodenum due to the action of bile and pancreatic enzymes, making it vital for nutrient absorption.
5. The duodenum has a rich blood supply to ensure that nutrients absorbed into its walls can quickly enter circulation.

Review Questions

• How does the structure of the duodenum facilitate its function in digestion?
  • The structure of the duodenum, with its C-shape and division into four segments, allows it to effectively mix chyme with bile and pancreatic juice. This mixing process enhances chemical digestion by ensuring that enzymes are evenly distributed throughout the food. Additionally, its mucosal lining is specialized for nutrient absorption, with villi and microvilli increasing surface area for efficient uptake of nutrients.
• Discuss the role of bile and pancreatic juices in digestion within the duodenum.
  • Bile, produced by the liver and stored in the gallbladder, is released into the duodenum to emulsify fats, breaking them down into smaller droplets for easier digestion. Pancreatic juices contain a variety of enzymes that further digest proteins, fats, and carbohydrates. Together, these fluids facilitate chemical digestion in the duodenum, allowing nutrients to be absorbed effectively into the bloodstream.
• Evaluate how hormonal regulation in the duodenum impacts overall digestive efficiency.
  • Hormones such as secretin and cholecystokinin are released by specialized cells in the duodenum in response to chyme entering from the stomach. Secretin stimulates the pancreas to release bicarbonate to neutralize gastric acid, while cholecystokinin promotes bile release from the gallbladder and enhances enzyme secretion from the pancreas. This hormonal regulation ensures that digestive processes occur optimally, increasing efficiency in nutrient absorption and maintaining intestinal health.

Related terms

Chyme: The semi-liquid mixture of partially digested food and gastric juices that exits the stomach and enters the duodenum.

Bile: A digestive fluid produced by the liver and stored in the gallbladder, released into the duodenum to help emulsify fats.

Pancreatic Juice: A fluid secreted by the pancreas containing enzymes that aid in the digestion of proteins, fats, and carbohydrates in the duodenum.