Jejunum

Definition

The jejunum is the second part of the small intestine, situated between the duodenum and the ileum. It plays a crucial role in the digestive process by facilitating the absorption of nutrients, including carbohydrates, proteins, and fats, into the bloodstream. The jejunum's structure, with its numerous folds and villi, enhances its surface area to maximize nutrient absorption.

5 Must Know Facts For Your Next Test

1. The jejunum is typically about 2.5 meters long and has a thicker wall compared to the ileum.
2. It has a rich blood supply, which is essential for transporting absorbed nutrients to the liver and other parts of the body.
3. The inner surface of the jejunum contains numerous circular folds called plicae circulares that aid in nutrient absorption.
4. Digestive enzymes from the pancreas and bile from the liver are secreted into the jejunum to help break down food particles.
5. Disorders affecting the jejunum, such as celiac disease or Crohn's disease, can lead to malabsorption and various nutritional deficiencies.

Review Questions

• How does the structure of the jejunum enhance its function in nutrient absorption?
  • The jejunum's structure significantly enhances its ability to absorb nutrients due to its large surface area created by folds, villi, and microvilli. These adaptations increase contact with digested food, allowing for more efficient absorption of carbohydrates, proteins, and fats into the bloodstream. Additionally, its rich vascular supply ensures that absorbed nutrients are quickly transported to other organs for use.
• Discuss the role of digestive enzymes and bile in the jejunum and their impact on nutrient absorption.
  • Digestive enzymes produced by the pancreas, along with bile from the liver, play a vital role in breaking down food substances within the jejunum. These substances help emulsify fats and hydrolyze carbohydrates and proteins into smaller components that can be easily absorbed. The efficiency of these enzymes directly impacts nutrient absorption rates, making their presence critical for optimal digestion in this segment of the small intestine.
• Evaluate the implications of diseases affecting the jejunum on overall health and nutritional status.
  • Diseases that affect the jejunum can severely impair nutrient absorption, leading to significant health issues such as malnutrition and vitamin deficiencies. Conditions like celiac disease or Crohn's disease disrupt normal digestive processes, causing inflammation or damage to the intestinal lining. This impairment results in decreased uptake of essential nutrients, which can have cascading effects on metabolic functions, immune response, and overall well-being.

Related terms

Duodenum:

The first section of the small intestine, where initial digestion occurs through the action of bile and pancreatic enzymes.

Ileum: The final section of the small intestine that absorbs vitamin B12 and bile salts before the remaining waste enters the large intestine.

Villi:

Tiny, finger-like projections lining the intestinal walls that increase surface area for absorption of nutrients.