Lecture Notes: Absorption in the Small Intestine

Introduction

• Focus on absorption process in the small intestine.
• Importance of breaking solid food into smaller pieces to increase surface area.
• Small intestine role: absorb nutrients efficiently into the bloodstream.

Structure of the Small Intestine

• Transverse Folds: Inside lining is folded to increase surface area.
• Villus: Structures on folds that aid in absorption.
• Columnar Epithelium: Lined with column-like cells, significant in absorption.
• Goblet Cells: Found among columnar cells; secrete mucus aiding in food lubrication and absorption.
• Cilia: Present on columnar epithelium to increase surface area.

Mitochondria in the Small Intestine

• High concentration due to need for energy in active transport.
• Cellular Respiration: Conversion of glucose into energy (ATP) for active transport.

Transport Mechanisms

• Passive Transport: Movement from high to low concentration, requires no energy.
  • Includes diffusion directly through membranes or via channel proteins.
• Active Transport: Movement from low to high concentration, against gradient, requires energy (ATP).
  • Essential in intestines for nutrient absorption.

Absorption of Nutrients

Carbohydrates and Proteins

• Monomers: Carbohydrates become monosaccharides; proteins become amino acids.
• Transport: Move through protein carriers into capillaries easily due to water solubility.
• Initial Passive Transport: From high to low concentration, then quickly shifts to active transport.

Fats

• Complex Absorption: Not water soluble, require breakdown before absorption.
• Components: Triglycerides are broken into glycerol (water soluble) and fatty acids (insoluble).
• Bile: Needed to help move fatty acids into villi.
• Lacteal: Specialized structure in villi for fat transport, part of the lymphatic system.
• Kyle: Term for fatty liquid in lacteal after absorption.

Vocab Recap

• Villi: Increase surface area, aid absorption, have microvilli.
• Microvilli: Further increase surface area.
• Columnar Epithelium: Column-like cells with mitochondria for absorption efficiency.
• Diffusion: Movement along concentration gradient; passive from high to low.
• Active Transport: Requires energy, moves from low to high concentration.
• Monosaccharides & Amino Acids: Monomers of carbohydrates and proteins, respectively.
• Lacteal: Part of the lymph system, transports fats as kyle.

Conclusion

• Understanding the structure and function of the small intestine is essential for grasping how nutrients are absorbed efficiently into the bloodstream.