Small Intestine and Absorption

Structure and Function

• The small intestine is a long organ with folds, villi, and microvilli.
• Purpose of Folds, Villi, and Microvilli
  • Surface Area: The folds increase the surface area significantly, improving absorption.
  • The increased surface area allows more opportunities for nutrient absorption.

Absorption Process

• Location: Occurs in the lining of the villi.
• Nutrients cross intestinal cells into transport systems.
• Essential for nutrients to be absorbed into the body for use by cells and organs.

Importance of Selective Absorption

• Cells on the brush border of the intestine are selective.
• Only specific recognized forms of nutrients are absorbed.
• Undigested particles are not absorbed, which can be affected by disease states like leaky gut.

Transport Systems

• Two Main Systems:
  1. Circulatory System (Red and Blue)
     • Transports water-soluble nutrients (amino acids, sugars, water-soluble vitamins).
     • Blood from the digestive tract first goes to the liver before circulating to the heart, lungs, and other tissues.
  2. Lymphatic System (Yellow)
     • Transports fats and fat-soluble vitamins.
     • Bypasses the liver initially, eventually joining the bloodstream near the heart, allowing nutrients to reach the body's cells.

Key Takeaways

• The structural design of the small intestine maximizes nutrient absorption.
• Nutrients utilize specific transport pathways for efficient delivery to cells.
• Understanding the difference between the circulatory and lymphatic systems is crucial for comprehending how nutrients are distributed throughout the body.