Miss Angler's Biology Class: Digestive System - Intestines

Introduction

• Focus on intestines (lower portion of the digestive system/Alimentary canal)
• Previous videos: mouth to stomach; future videos: digestion and absorption
• Reminder to subscribe and turn on notifications

Structure of the Intestines

• Accessory organs involved: liver, gallbladder, pancreas

Small Intestine Adaptations

• Villi and Microvilli: Increase surface area for absorption
• Transverse Folds: Also increase surface area
• Thin Walls: One cell layer thick for efficient diffusion
• Length: Approximately 7 meters, allows more time for absorption
• Capillary Network: Facilitates faster absorption into bloodstream

Regions of the Small Intestine

1. Duodenum
   • Connected to the stomach
   • Crypts of Lieberkühn: Secretes hormone secretin
   • Secretin: Stimulates pancreas to secrete pancreatic juice
   • Pancreatic Juice: Neutralizes acidic chyme, making it alkaline
   • Bile from Liver: Stored in gallbladder, emulsifies fats
   • Bicarbonate Mucus: Secreted to neutralize acidity and protect intestinal lining
   • Amylase: Enzyme for breaking down carbohydrates
2. Jejunum
   • Main region for absorption
   • Structures: Villi, Microvilli, Lacteals (absorb fats), Capillary bed (absorb proteins and carbs)
   • Epithelial cells: Facilitate diffusion
   • Goblet cells: Secrete mucus and maintain water balance
3. Ileum
   • Connects to large intestine
   • Ileocecal Valve: Controls the passage of food between small and large intestine

Large Intestine

• Function: Absorb water, form feces

Regions of the Large Intestine

1. Cecum
   • Connects to ileum
   • Contains the appendix (maintains gut bacteria)
2. Ascending Colon: Moves food upward
3. Transverse Colon: Moves food across
4. Descending Colon: Moves food downward
5. Rectum: Stores feces
6. Anus: Sphincter muscles control defecation

Terminology Recap

• Villi: Finger-like projections in the small intestine
• Microvilli: Hair-like projections on villi
• Duodenum: First part of the small intestine
• Crypts of Lieberkühn: Gland in the duodenum
• Secretin: Hormone stimulating pancreatic juice secretion
• Pancreatic Juice: Neutralizes chyme
• Bile: Emulsifies fats, produced by liver, stored in gallbladder
• Succus Entericus: Combination of pancreatic juice, bile, and mucus
• Jejunum: Main absorption area
• Ileocecal Valve: Controls passage to large intestine
• Cecum: Beginning of large intestine
• Appendix: Bacterial population maintenance
• Ascending/Transverse/Descending Colon: Sections of the large intestine
• Rectum: Stores feces
• Anus: Controls defecation