Jejunum

Definition

The jejunum is the second part of the small intestine, located between the duodenum and the ileum. This segment is primarily responsible for the absorption of nutrients from digested food, making it a crucial component of the digestive system's anatomy and physiology. The jejunum has specialized structures that increase its surface area, facilitating efficient nutrient absorption.

5 Must Know Facts For Your Next Test

1. The jejunum typically constitutes about 2.5 meters (8 feet) of the small intestine and is where most nutrient absorption occurs.
2. It has a thicker wall and a larger diameter compared to other parts of the small intestine, allowing for increased absorption capabilities.
3. The lining of the jejunum contains numerous folds, known as plicae circulares, which enhance surface area further for better nutrient uptake.
4. Blood supply to the jejunum comes primarily from the jejunal arteries, which branch off from the superior mesenteric artery.
5. The jejunum absorbs a wide variety of nutrients including carbohydrates, proteins, fats, vitamins, and minerals, playing a vital role in overall nutrition.

Review Questions

• How does the structure of the jejunum facilitate its role in nutrient absorption?
  • The structure of the jejunum is specifically designed to maximize nutrient absorption. It features a larger diameter and thicker walls compared to other sections of the small intestine, allowing for increased capacity. The presence of villi and plicae circulares creates a significantly larger surface area for absorption, making it highly efficient in taking up essential nutrients from digested food.
• What are the main differences in function and structure between the jejunum and ileum?
  • While both the jejunum and ileum are parts of the small intestine involved in nutrient absorption, they have distinct functions and structural differences. The jejunum is primarily responsible for absorbing carbohydrates, proteins, and fats, whereas the ileum focuses on absorbing vitamin B12 and bile salts. Structurally, the jejunum has thicker walls and more plicae circulares compared to the ileum, which has fewer folds and a thinner wall.
• Evaluate how conditions affecting the jejunum might impact overall nutritional status in an individual.
  • Conditions such as celiac disease or Crohn's disease that affect the jejunum can significantly impact an individual's nutritional status. Since this segment is crucial for absorbing essential nutrients, damage or inflammation can lead to malabsorption. This malabsorption may result in deficiencies in carbohydrates, proteins, fats, vitamins, and minerals, potentially causing a range of health issues including weight loss, anemia, and weakened immune function.

Related terms

Duodenum:

The first part of the small intestine, where initial digestion occurs, receiving chyme from the stomach and secretions from the pancreas and liver.

Ileum: The final section of the small intestine that connects to the large intestine, responsible for absorbing vitamin B12 and bile salts.

Villi: Tiny, finger-like projections on the inner surface of the small intestine that increase the surface area for absorption of nutrients.