Absorption in the Small Intestine

Overview

• Absorption in the small intestine involves breaking down solid food into smaller pieces to increase surface area for nutrient absorption.
• The small intestine has a specialized structure with transverse folds and villi to increase efficiency.

Structure of the Small Intestine

• Villi: Structures that line the small intestine to increase surface area.
• Columnar Epithelium: Cells that resemble columns, packed closely together.
  • Contain goblet cells which secrete mucus, aiding in lubrication and absorption.
  • Have cilia to further increase surface area.
  • Rich in mitochondria for energy production, facilitating active transport.

Transport Mechanisms

• Passive Transport:
  • Moves substances from high to low concentration.
  • Requires little to no energy.
  • Involves diffusion and passage through channel proteins.
• Active Transport:
  • Moves substances from low to high concentration against the gradient.
  • Requires energy (ATP) and involves channel proteins.
  • Facilitated by mitochondria in columnar epithelium.

Absorption Processes

• Carbohydrates and Proteins:
  • Digested into monomers: monosaccharides and amino acids.
  • Move via protein carriers into capillaries.
  • Start with passive transport, often transitioning to active transport.
• Fats:
  • More complex as they are not water-soluble.
  • Triglycerides broken into glycerol and fatty acids.
  • Glycerol: Water-soluble, absorbed easily.
  • Fatty Acids: Combined with bile to facilitate movement into villi.
  • Absorbed into the lacteal (part of the lymph system), forming chyle.

Recap of Key Terms

• Villi and Microvilli: Increase surface area for absorption.
• Columnar Epithelium: Cells aiding in absorption, filled with mitochondria.
• Diffusion: Movement along concentration gradient; typically passive.
• Active Transport: Movement against concentration gradient; requires energy.
• Monosaccharides and Amino Acids: The simplest forms of carbohydrates and proteins.
• Glycerol and Fatty Acids: Components of fats requiring unique absorption paths.
• Lacteal: Specialized structure for fat absorption into the lymph system, forming chyle.

Thank you for listening to the lecture. Use these notes to consolidate what you've learned.