Ileum

Definition

The ileum is the final section of the small intestine, extending from the jejunum to the cecum of the large intestine. It plays a crucial role in nutrient absorption, especially for vitamin B12 and bile salts, while also serving as a key site for immune function due to its association with lymphoid tissue known as Peyer's patches.

5 Must Know Facts For Your Next Test

1. The ileum is about 3-4 meters long in adults and has a smaller diameter than the other sections of the small intestine.
2. It is rich in villi and microvilli, which increase the surface area for optimal nutrient absorption.
3. The ileocecal valve controls the flow of material from the ileum into the cecum, preventing backflow into the ileum.
4. Bile salts absorbed in the ileum are recycled back to the liver through the enterohepatic circulation, essential for fat digestion.
5. Malabsorption syndromes can affect the ileum's ability to absorb nutrients, leading to deficiencies, particularly of vitamin B12.

Review Questions

• How does the structure of the ileum facilitate its function in nutrient absorption?
  • The structure of the ileum, featuring numerous villi and microvilli, greatly enhances its surface area, allowing for efficient absorption of nutrients. These projections are lined with epithelial cells that transport nutrients directly into the bloodstream. Additionally, specialized cells help absorb specific nutrients like vitamin B12 and bile salts, making the ileum vital for effective digestion and nutrient uptake.
• Discuss the significance of Peyer's patches in the ileum regarding immune function.
  • Peyer's patches are important lymphoid tissues located in the ileum that play a key role in immune surveillance. They help monitor intestinal bacteria and maintain gut flora balance. By sampling antigens from intestinal contents, Peyer's patches contribute to mucosal immunity, enabling the body to respond effectively to pathogens while promoting tolerance to non-harmful antigens.
• Evaluate how conditions affecting the ileum can lead to systemic health issues beyond nutrient absorption.
  • Conditions such as Crohn's disease or celiac disease can significantly impair ileal function, resulting in malabsorption of essential nutrients like vitamin B12 and iron. This deficiency can lead to anemia and other systemic health issues, including fatigue, neurological problems, and immune dysfunction. Furthermore, chronic inflammation in the ileum can impact overall gut health and disrupt microbiota balance, leading to broader gastrointestinal and metabolic complications.

Related terms

Duodenum:

The first segment of the small intestine, where initial digestion occurs and pancreatic enzymes and bile are introduced.

Jejunum:

The middle section of the small intestine, primarily responsible for the absorption of carbohydrates and proteins.

Peyer's patches: Aggregated lymphoid nodules found in the ileum that play a critical role in the immune response by monitoring intestinal bacteria and preventing growth of pathogenic bacteria.