Ileum

Definition

The ileum is the final section of the small intestine, following the jejunum, and plays a critical role in the digestion and absorption of nutrients, particularly lipids. This part of the digestive system is specialized for the absorption of bile salts and vitamin B12, and it features numerous villi and microvilli that increase the surface area for nutrient uptake.

5 Must Know Facts For Your Next Test

1. The ileum absorbs about 90% of bile salts and recycles them back to the liver through the enterohepatic circulation.
2. It is approximately 3 to 4 meters long in adults and contains a high density of lymphoid tissue, which plays a role in immune function.
3. Fat-soluble vitamins (A, D, E, K) are primarily absorbed in the ileum due to its specialized absorption capabilities.
4. Disruption or disease affecting the ileum can lead to malabsorption syndromes, impacting overall health.
5. The ileocecal valve regulates the flow of material from the ileum into the cecum of the large intestine, preventing backflow.

Review Questions

• How does the structure of the ileum facilitate lipid absorption compared to other parts of the intestine?
  • The structure of the ileum, with its extensive villi and microvilli, provides a vast surface area for nutrient absorption, making it particularly effective at absorbing lipids. Specialized transport mechanisms within the ileal cells allow for efficient uptake of fatty acids and monoglycerides after they have been emulsified by bile salts. Compared to other sections like the duodenum or jejunum, which also absorb nutrients, the ileum's unique adaptations enhance its ability to handle lipids and specific vitamins.
• Discuss how bile salts interact with lipids in the ileum during digestion and absorption.
  • Bile salts play a vital role in lipid digestion and absorption in the ileum by emulsifying dietary fats into smaller micelles. This process increases the surface area of lipids, making them more accessible to digestive enzymes like pancreatic lipase. Once emulsified, fatty acids and monoglycerides can be absorbed by enterocytes in the ileal lining. After absorption, bile salts are reabsorbed in the ileum and sent back to the liver, showcasing a critical recycling mechanism essential for lipid metabolism.
• Evaluate the consequences of an ileal resection on lipid digestion and nutrient absorption.
  • An ileal resection can lead to significant consequences for lipid digestion and overall nutrient absorption due to its specialized functions. The loss of this section may result in impaired absorption of bile salts and fat-soluble vitamins, leading to deficiencies such as fat malabsorption syndromes. This condition can cause weight loss, diarrhea, and nutritional deficiencies over time. Furthermore, patients may require dietary modifications or supplementation to manage these deficiencies and ensure adequate nutrient intake post-surgery.

Related terms

Chylomicrons:

Chylomicrons are lipoprotein particles that transport dietary lipids from the intestines to other locations in the body through the lymphatic system.

Bile Salts: Bile salts are compounds derived from cholesterol that aid in the emulsification and absorption of dietary fats in the small intestine.

Villi: Villi are small, finger-like projections lining the intestinal wall that significantly increase the surface area for nutrient absorption.