AP TEST 3

Digestive System & GI Tract

1. Two main sets of organs in the digestive system

   • Gastrointestinal (GI) Tract: Continuous tube from mouth to anus (e.g., stomach, intestines).

   • Accessory Organs: Aid in digestion but food doesn’t pass through them (e.g., liver, pancreas, gallbladder).

2. Structure of the GI Tract

   • Hollow tube with four tunic layers (mucosa, submucosa, muscularis, serosa).

   • Varies in structure along its length for specialized functions.

3. Six parts of the GI Tract

   • Mouth, Esophagus, Stomach, Small Intestine, Large Intestine, Anus

4. Digestive System Accessory Organs

   • Teeth, Tongue, Salivary Glands, Liver, Gallbladder, Pancreas

5. Six Stages of Digestion

   • Ingestion: Food enters the mouth.

   • Propulsion: Swallowing & peristalsis move food.

   • Mechanical Digestion: Physical breakdown (chewing, stomach churning).

   • Chemical Digestion: Enzymatic breakdown of macromolecules.

   • Absorption: Nutrients enter blood/lymph.

   • Defecation: Elimination of indigestible waste.

6. Four Tunic Layers of the GI Tract

   • Mucosa: Innermost; secretes mucus & enzymes, absorbs nutrients.

   • Submucosa: Connective tissue with blood vessels, lymph, and nerves.

   • Muscularis: Smooth muscle; responsible for peristalsis.

   • Serosa: Outer layer; reduces friction.

7. Structure of the Stomach

   • Histology: Modified muscularis with extra oblique layer for mixing.

   • Gastric Pits: Contain chief cells (pepsinogen), parietal cells (HCl, intrinsic factor), mucus cells.

   • Sphincters: Lower esophageal (cardiac) sphincter (in), pyloric sphincter (out).

8. Regulation of Gastric Secretion (Three Phases)

   • Cephalic Phase: Brain signals stomach (smell, taste).

   • Gastric Phase: Food in stomach; stimulates acid/enzyme release.

   • Intestinal Phase: Chyme enters small intestine; slows gastric activity.

9. Structure of the Small Intestine & Villi

   • Three sections: Duodenum, Jejunum, Ileum.

   • Villi: Fingerlike projections that increase surface area for absorption.

10. Role of Bile

• Produced in liver, stored in gallbladder.

• Emulsifies fats for easier digestion by lipases.

• Secreted in response to CCK hormone.

11. Pancreas Function & Secretions

• Endocrine (insulin, glucagon) & exocrine (digestive enzymes, bicarbonate).

• Stimulated by secretin & CCK.

12. Movement of Nutrients through Epithelial Villi

• Nutrients diffuse or actively transport into capillaries or lacteals.

13. Absorption of Carbs, Fats, Proteins

• Carbs → Monosaccharides → Blood.

• Fats → Fatty acids → Lymph (via lacteals).

• Proteins → Amino acids → Blood.

14. Why Long-Chain Fatty Acids Don’t Enter Capillaries

• Too large; enter lacteals (lymphatic vessels) first.

15. Histological Differences in Large Intestine

• More goblet cells for mucus production.

• No villi (less absorption, except water/electrolytes).

16. Eight Divisions of the Large Intestine

• Cecum, Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum, Anal Canal, Anus.

17. Teniae Coli & Haustra

• Teniae Coli: Three bands of smooth muscle.

• Haustra: Pouches formed by teniae coli contractions.

18. Chemical Digestion Breakdown

• Carbs → Amylase → Glucose.

• Fats → Lipase + Bile → Fatty acids.

• Proteins → Pepsin + Proteases → Amino acids.

• Nucleic Acids → Nucleases → Nucleotides.

19. Digestion Chart Review

• Be familiar with enzymes, locations, and absorbed products.

Nutrition & Metabolism

1. Metabolism

   • Sum of all chemical reactions in the body.

2. Nutrient

   • Substance needed for growth, maintenance, and repair.

3. Macronutrients vs. Micronutrients

   • Macronutrients: Carbs, fats, proteins (needed in large amounts).

   • Micronutrients: Vitamins, minerals (needed in small amounts).

4. Essential Nutrient

   • Body cannot synthesize it; must be obtained from diet.

5. Carbohydrates

   • Source: Plants (grains, fruits, vegetables).

   • Purpose: Primary energy source.

   • Classes: Monosaccharides, disaccharides, polysaccharides.

6. Glucose & Fat Interchangeability

   • Excess glucose stored as fat; fat can be converted to glucose.

7. Carbohydrate Dietary Requirements

   • 45–65% of daily intake

8. Glucose & Blood Sugar

   • Maintains homeostasis; insulin lowers, glucagon raises.

9. Do Lipids Have More Energy Than Carbs?

   • Yes, 9 kcal/g vs. 4 kcal/g for carbs.

10. Why We Need Lipids

• Cell membranes, energy storage, hormone production.

11. Types of Lipids

• Triglycerides, phospholipids, steroids.

12. Lipid Requirements

• 20–35% of total daily intake.

13. Protein Function

• Builds tissues, enzymes, hormones.

14. Complete Protein

• Contains all essential amino acids.

15. Are Plants Complete Proteins?

• No, except soy & quinoa.

16. All or None Rule (Proteins)

• All essential amino acids must be present for protein synthesis.

17. Positive Nitrogen Balance

• Protein intake > protein breakdown (growth, pregnancy).

18. Hormonal Control of Blood Glucose & Protein Synthesis

• Insulin promotes glucose uptake; glucagon increases glucose release.

19. Protein Requirements

• 10–35% of daily intake.

20. Vitamins & Minerals

• Vitamins: Organic, essential nutrients.

• Minerals: Inorganic elements needed for body function.

21. Anabolism vs. Catabolism

• Anabolism: Building molecules.

• Catabolism: Breaking down molecules for energy.

22. End Result of Glucose Catabolism

• ATP production.

23. Three Stages of Catabolism

• Glycolysis, Krebs Cycle, Electron Transport Chain.

24. Glycogenesis, Glycogenolysis, Gluconeogenesis

• Glycogenesis: Glucose → Glycogen (storage).

• Glycogenolysis: Glycogen → Glucose (release).

• Gluconeogenesis: Non-carb sources → Glucose.

25. Fed State vs. Post-Absorptive State

• Fed: Nutrient absorption occurring.

• Post-Absorptive: Between meals; body relies on stores.

26. Glucose Sparing

• Body preserves glucose for brain by using fats/proteins for energy.

27. Metabolic Rate, BMR, TMR

• BMR: Resting energy use.

• TMR: Total daily energy use.