Digestive System Functions Quiz

Course Information

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

Learning Outcomes

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

Digestion

• This is the breaking-down of nutrients into their smallest parts.
• Brightspace contains relevant videos and links.

Digestive System - Where Does Food Travel?

• Diagram of the digestive system, labeling the different parts involved in the pathway of food.

Digestive System - Accessory Organs

• Diagram of the digestive system, labeling the accessory organs.

Human Digestion

• The act of breaking down nutrients into their smallest components involves several nutrients. Some examples are: carbohydrates, fats (lipids), proteins, vitamins, minerals, and water.

Human Digestion - Mechanical Digestion

• Involves physically breaking down food into smaller parts using: teeth (chewing), stomach (muscular contractions), and muscular contractions (peristalsis).

Human Digestion - Chemical Digestion

• Enzymes speed up chemical breakdown.
• Acids (hydrochloric acid—gastric juice) break down chemical bonds in food.

Digestive System

• The gastrointestinal (GI) tract is a 30-foot-long hollow tube.
• The lumen is lined by mucosal cells.
• The GI tract supplies the body with constant water and nutrients by secretion of digestive juices and enzymes, digestion of food, absorption of water and nutrients, and the distribution of these absorbed nutrients to circulating blood.

Digestive System Functions

• Each part of the digestive tract has specific functions that are essential for its process, these include:
• Passage of food, temporary storage, digestion of food, absorption of food, and waste elimination.

Mouth-Structure, Enzymes, and Secretions

• Teeth
• Taste buds
• Saliva (1-1.5 liters produced daily), moistens, containing enzymes (salivary amylase).
• Saliva carries taste to taste buds.
• Saliva protects teeth and forms a protective coating over them

Throat (Pharynx) - Structure, Enzymes, and Secretions

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

Esophagus

• Connects the pharynx to the stomach.
• Rhythmic muscle contractions (peristalsis) move food bolus.
• Food passes through a muscular ring to enter the stomach.
• No digestion occurs in the esophagus.

Stomach - Structures, Enzymes, and Secretions

• Temporary storage until processing.
• Mechanical and chemical digestion.
• Gastric glands produce gastric juice containing water.
• Pepsin (inactive form) is a protein-digesting enzyme.
• Kills microorganisms, unfolds proteins, activates pepsinogen to pepsin.

Stomach

• Stomach acid protects the stomach lining from pepsin and hydrochloric acid.
• Chyme is a semi-liquid blend of foods and gastric secretions.
• Chyme leaves the stomach through the pyloric sphincter and enters the small intestine. 

Stomach Emptying

• Regulated by chyme and signals from different parts, small intestine, and even the brain.
• Affected by meal size (large meal > small meal > liquid meal), meal composition (fat > fiber and protein > carbohydrates and sugars), and affects satiety.

Small Intestine (Structure, Enzymes, and Secretions)

• The primary site for chemical digestion and absorption.
• Comprised of three parts.
• Accessory organs play a crucial role in this process.

Accessory Organs

• Organs like the pancreas, liver, and gallbladder.
• Pancreas produces bicarbonate, Pancreatic amylase, Protease and Lipase.
• The liver creates bile and stores it in the gallbladder. 

Bile's Role

• Emulsifies lipids (mechanical digestion).
• Makes fat particles smaller for enzyme action.
• Lipases break bonds to release glycerol and fatty acids (chemical digestion).

Large Intestine

• Absorbs water and some vitamins.
• Fibre takes action and prebiotics and probiotics are involved in the function of the large intestine.

Rectum

• Storage area for wastes.
• Expels wastes through the anus.

Transit Time

• The time it takes for food to travel from mouth to anus varies depending on multiple factors, including the diet, physical activity level, health status, and use of laxatives.
• Mouth to small intestine (6-8 hours)
• Mouth to large intestine (~40 hours). 

Transit Time Impacts

• Diet composition (meat takes longer than fiber/water)
• Physical activity level, Emotional state
• Health status (diarrhea = very fast)
• Use of laxatives

Absorption

• Most happens in the small intestine.
• Once nutrients are digested into their smallest molecules (nutrients), they cross the gastrointestinal wall into the circulatory system.
• Folds, villi, and microvilli in small intestines increase surface area for maximum absorption of nutrients.

Methods of Absorption

• Passive/Simple diffusion
• Facilitated diffusion
• Active transport

Passive Diffusion

• Nutrients absorbed due to a concentration gradient.
• No energy required if the concentration of the substance is higher on one side of the membrane than the other.

Facilitated Diffusion

• Similar to passive diffusion, from high to low concentration.
• No energy required. A special protein carrier is for nutrients across.

Active Transport

• Nutrients absorbed from a low to high concentration by requiring energy and a carrier.

Post-Absorption

• Circulatory/cardiovascular system.
• Urinary system (Waste removal)

Movement of Nutrients 

• Water soluble nutrients enter the capillaries in the villi>hepatic portal vein (bloodstream)>liver. 
• Fat soluble nutrients enter the lymphatic system > blood.

Circulatory / Cardiovascular System

• Transports nutrients to cells and waste away from cells.
• Consists of heart, blood, and blood vessels.
• Nutrients are absorbed in the small intestine, travel to the liver via the hepatic portal vein, then to the heart through the inferior vena cava, then to the lungs to get oxygen. The oxygenated blood travels to all body cells.

Liver

• Collects absorbed nutrients.
• Stores nutrients.
• Converts nutrients into usable substances.
• Filters and removes harmful substances.

Lymphatic System

• Removes fluid and impurities from tissues into the blood.
• Involved in the immune system, containing immune cells that fight antigens.
• Transports fat-soluble nutrients and waste products. 

Waste Removal

• Undigested/unabsorbed materials (feces) exit via the GI tract.
• Kidneys filter excess water and waste, excreting excess as urine.
• Lungs exhale carbon dioxide and water vapor.
• Skin excretes waste through sweat.

Excretion and Waste

• Urine color chart and Bristol Stool Chart are provided as a reference.

Review Differences 

• Digestion: food breakdown.
• Absorption: nutrients enter the body. 
• Metabolism: what happens to nutrients inside the body.

Metabolism

• The use of absorbed nutrients for energy production and larger structure building.
• Breaking down larger structures to create energy.

Digestive System Summary

• Summary chart of the digestive system with important factors.

Student Independent Activity

• Review the Allergies and Intolerances section.

Outcome Reviews

• Summarizing the key outcomes covered in the presentation.

Participation Activity

• Instructions to participate in a Kahoot!.