Eating and Human Digestion Quiz

Course Information

• Course title: Eating and Human Digestion
• Course code: NUTR 1100
• Instructor: Stephanie Gladman, MHSc, RD (Registered Dietitian)
• Institution: Langara College

Learning Outcomes

• Recall the anatomy and function of the gastrointestinal tract, and the role of its major structures.
• Describe nutrition-related physiological processes, including digestion, absorption, transport, and elimination, and their role in delivering and using energy and nutrients in the body.
• Differentiate between water-soluble and fat-soluble absorption, including the systems used and reasoning.
• Describe metabolism processes and the role of energy and nutrients in the body.

Digestion

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Digestive System - Where does food travel?

• Diagram showing the path of food through the digestive system

Digestive System - Accessory Organs

• Diagram showing the accessory organs of the digestive system.

Human Digestion

• Food is broken down into its smallest parts, which are the nutrients:
  • Carbohydrates
  • Fats (lipids)
  • Proteins
  • Vitamins
  • Minerals
  • Water

Human Digestion - Mechanical Digestion

• Food is broken down into smaller parts through:
  • Teeth (chewing)
  • Stomach (smooth muscles)
  • Muscular contractions (peristalsis)

Human Digestion - Chemical Digestion

• Enzymes speed up the chemical breakdown of food.
• Acids (hydrochloric acid - gastric juice) break down chemical bonds.

Digestive System

• Gastrointestinal (GI) tract: a 30-foot long hollow tube, with a lumen (inside space) lined by mucosal cells.
• The GI tract constantly supplies the body with water and nutrients.
  • Secretion of digestive juices and enzymes
  • Passage of food through the tract
  • Digestion of food
  • Absorption of water and nutrients
  • Circulating blood to distribute absorbed nutrients
• Each part of the digestive tract has specific functions:
  • Passage of food
  • Temporary storage
  • Digestion of food
  • Absorption of food
  • Elimination of waste

Structure, Enzymes, and Secretions - Mouth

• Teeth
• Taste buds
• Saliva (1-1.5 liters produced daily)
  • Moistens
  • Contains enzymes (salivary amylase) which break down starch.
  • Protects teeth.
  • Forms a protective layer.

Structure, Enzymes, and Secretions - Throat (Pharynx)

• Trachea → lungs
• Esophagus → stomach
• Epiglottis: prevents food from going down the wrong tube

Structure, Enzymes, and Secretions - Esophagus

• Connects pharynx to stomach
• Bolus of food is moved by rhythmic muscle contractions (called peristalsis).
• Food passes through a muscular ring (sphincter) to enter the stomach.
• No digestion takes place in the esophagus.

Structure, Enzymes, and Secretions - Stomach

• Temporary storage until processed.
• Mechanical + chemical digestion.
• Gastric glands produce gastric juices containing:
  • Water
  • Pepsin (inactive protein-digesting enzyme)
  • Kills microorganisms, unfolds proteins, and activates pepsinogen to pepsin. Also inhibits amylase (breaks down starch).
• Chyme: a semi-liquid blend of foods and gastric secretions.
• It leaves the stomach through the pyloric sphincter to enter the small intestine.
• Protects stomach lining from pepsin and hydrochloric acid

Structure, Enzymes, and Secretions - Stomach Emptying

• Regulated by chyme and signals from nerves and hormones.
• Affected by:
  • Meal size (large > small > liquid)
  • Meal composition (fat > fiber > carbohydrates and sugars)
  • Affects satiety; importance of a balanced meal.

Structure, Enzymes, and Secretions - Small Intestine

• Main site of chemical digestion and absorption.
• Has three parts.
• Accessory organs play a role:
• Bicarbonate
• Pancreatic amylase
• Protease
• Lipase
• Makes bile
• Stores bile

Structure, Enzymes, and Secretions - Bile

• Emulsifies lipids (fats) - a type of mechanical digestion.
• Makes fat particles small enough for enzymes to break down chemical bonds.
• Lipases (enzymes) break down those bonds, releasing glycerol and fatty acids – chemical digestion.

Structure, Enzymes, and Secretions - Large Intestine

• Things not absorbed.
• Some absorption happens:
  • Water
  • Vitamins (e.g., vitamin K)
  • Fiber
  • Prebiotics
  • Probiotics

Structure, Enzymes, and Secretions - Rectum

• Storage area
• Packs waste, expels through anus.

Transit Time

• Time from mouth to anus varies.
• Mouth to small intestine: 6-8 hours
• Mouth to large intestine: ~40 hours
• Diet, physical activity, emotional state, health status, and laxative use affect transit time.
  • Shorter time = healthier intestinal wall
  • Longer time = more harmful bacteria produced.

Absorption

• Most absorption happens in the small intestine.
• Digested food (nutrients) must cross the gastrointestinal wall into the circulatory system.
• Small intestine has folds, villi, and microvilli for maximum nutrient absorption.
• Diagrams show structure of the small intestine (folds, villi, microvilli, capillaries, lacteals, etc.)
• Three methods of absorption:
  • Passive/Simple diffusion
  • Facilitated diffusion
  • Active transport

Passive/Simple Diffusion

• Nutrients absorbed due to a concentration gradient.
• No energy required.
• Concentration greater in GI tract than inside intestinal wall.

Facilitated Diffusion

• Similar to passive diffusion (high to low concentration).
• No energy required.
• Requires special protein carriers to transport nutrients.

Active Transport

• Absorbs nutrients from low to high concentration.
• Requires energy and a carrier.

Post Absorption

• Circulatory/cardiovascular system
• Urinary system
• Waste removal

Movement of Nutrients

• Water-soluble nutrients: transported through capillaries in the villi to the hepatic portal vein, then to the liver.
• Fat-soluble nutrients packaged in protein vehicles into the lymph system.

Circulatory/Cardiovascular System

• Transports nutrients to cells and waste away from cells.
• Consists of heart, blood, and blood vessels.
• Nutrients absorbed in small intestine, travel to liver, then to the heart, lungs, and then all body cells.

Liver

• Collects nutrients absorbed in the digestive tract.
• Stores nutrients.
• Converts nutrients into substances usable by the body.
• Filters blood and removes harmful substances.

Lymphatic System

• Removes fluid from tissues.
• Filters fluid before returning to blood.
• Involved in immunity (contains immune cells to fight antigens).
• Transports and absorbs fat-soluble nutrients.

Waste Removal

• Undigested/unabsorbed materials (feces): removed through the GI tract.
• Metabolic wastes removed through:
  • Kidneys (filter water and small molecules, excretes excess as urine).
  • Lungs (remove CO2 and water).
  • Skin (removes water, minerals, and N-containing wastes through sweat)

Excretion and Waste

• Urine color chart
• Bristol stool chart

Review Differences

• Digestion: Breaking down food into simple nutrients.
• Absorption: Nutrients enter the body by crossing the gastrointestinal wall and entering the circulatory system.
• Metabolism: What happens to nutrients once inside the body.

Metabolism

• Nutrients used for energy.
• Larger structures are built (requires energy).
• Larger structures broken down (creates energy).

Digestive System Summary

• Diagram summarizing major structures and functions of the digestive system.

Student Independent Activities

• Review Allergies and Intolerances section.

Outcome Reviews

• Outcomes of the class
• Summarized knowledge learned in the lecture.

Participation Activity

• Instructions to join a Kahoot! quiz.
• Kahoot! instructions

Test your knowledge on the anatomy and function of the gastrointestinal tract. This quiz covers digestion, absorption, and metabolism processes essential for delivering energy and nutrients in the body. Differentiate between water-soluble and fat-soluble absorption along the way.