Digestion Basics and Salivary Enzymes

Digestion Basics

• Digestion breaks down food into absorbable units.
• Macronutrients are carbohydrates, fats, and proteins.
• Micronutrients are vitamins and minerals.
• The digestive tract is a long tube from mouth to anus.

Salivary Enzymes

• Saliva contains amylase (carbohydrate digestion) and lipase (fat digestion).
• Salivary amylase initiates carbohydrate digestion.
• Salivary lipase starts fat digestion.
• Chewed food mixed with saliva forms a bolus.
• Salivary glands secrete saliva.

Esophagus and Stomach

• The bolus moves from the esophagus to the stomach.
• The lower esophageal sphincter controls stomach entry.
• A leaky lower esophageal sphincter can cause heartburn.
• Stomach secretions include:
  • Hydrochloric acid (HCl)
  • Pepsin (protein digestion)
  • Gastric Lipase (continues fat digestion).
• The stomach churns food, creating chyme.
• Chyme is the liquid mixture of food that leaves the stomach.

Small Intestine

• Chyme passes from the stomach to the duodenum via the pyloric sphincter.
• The pyloric sphincter controls chyme release from the stomach into the small intestine.
• Bile, produced in the liver and stored in the gallbladder, aids fat digestion.
• Bile emulsifies fats in the duodenum.
• The pancreas releases enzymes into the duodenum:
  • Pancreatic amylase (continues carbohydrate digestion)
  • Pancreatic lipase (continues fat digestion)
  • Trypsin (protein digestion)
  • Chymotrypsin (protein digestion)
• The ~15-30 foot small intestine breaks down food into absorbable units.
• The small intestine is a long, coiled tube, where food is broken down and absorbed.
• Parts of the small intestine: duodenum, jejunum, ileum.

Large Intestine

• The small intestine connects to the large intestine via the ileocecal valve.
• The large intestine absorbs water and some solutes.
• Feces are stored and dried in the large intestine.
• Parts of the large intestine: ascending, transverse, descending, sigmoid colon.
• Feces are formed and expelled through the anus.

Villus Structure

• The small intestine's inner lining has villi (finger-like projections) increasing surface area for absorption.
• Microvilli further increase surface area, forming the brush border.
• Enterocytes (cells in the brush border) facilitate nutrient absorption.
• Villi are finger-like projections in the small intestine that increase surface area for absorption.
• Microvilli are hair-like projections on villi, further increasing surface area.
• Enterocytes are cells that make up the microvilli and aid in nutrient absorption

Nutrient Absorption

• Fats are absorbed into the central lacteal within each villus, entering the lymphatic system.
• Proteins and carbohydrates are absorbed directly into the bloodstream via surrounding capillaries.
• The central lacteal is a lymphatic vessel within each villus.
• Fats are absorbed into the central lacteal and transported through the lymphatic system.
• Blood capillaries surround each villus.
• Proteins and carbohydrates are absorbed into the bloodstream.

Appendix

• The appendix, a small pouch near the cecum, can become inflamed (appendicitis) if blocked.
• The appendix is a small pouch at the beginning of the large intestine.

Additional Notes

• Digestion begins in the mouth with chewing.
• Saliva contains enzymes that begin the digestion of carbohydrates and fats.
• Chewed food is swallowed as a bolus.
• The bolus passes down the esophagus.
• The esophagus connects the mouth to the stomach.

Explore the fundamentals of digestion, starting from the mouth to the stomach. Learn about macro and micro nutrients, the role of saliva and enzymes like amylase and lipase, and how food travels through the digestive tract. This quiz delves into the functions and processes essential for breaking down food.