Digestive System and Nutrients: A Comprehensive Overview

Symptoms and Essential Components

• A symptom of lactose intolerance is bloating, gas, or diarrhea.
• Food contains nutrients and energy to keep our bodies working properly.
• The digestive system breaks down food into smaller molecules to absorb nutrients and eliminate waste.

ATP: The Energy Currency

• The purpose of ATP is to provide energy for cellular processes.
• Two uses for ATP:
  • Muscle contraction
  • Active transport of molecules across cell membranes
• ATP becomes ADP (adenosine diphosphate) and a phosphate group when used by the body.

Major and Minor Nutrients

• Major nutrients:
  • Carbohydrates
  • Proteins
  • Fats
• Minor nutrients:
  • Vitamins
  • Minerals

Major Nutrients - Carbohydrates

• Main source of energy.
• Three sizes:
  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Storage form of carbohydrates:
  • Plants: starch
  • Animals: glycogen

Major Nutrients - Proteins

• Functions:
  • Build and repair tissues
  • Enzymes
  • Hormones and immune function
• Made up of 20 different amino acids.
• Essential amino acids must come from food.

Major Nutrients - Fats (Lipids)

• Functions:
  • Long-term energy storage
  • Protect organs and insulate body
  • Make cell membranes and hormones
• Oils are liquid at room temperature, fats are solid.
• Three kinds:
  • Saturated (all hydrogens attached)
  • Unsaturated (not all hydrogens attached)
  • Trans

Vitamins and Minerals

• Vitamins help regulate body processes and support immune function.
• Minerals build bones, teeth, and are needed for nerve function and muscle contraction.

The Digestive System

• A series of organs that break down food into nutrients the body can absorb and use.
• As food passes through, it is mechanically and chemically broken down, nutrients are absorbed, and waste is eliminated.
• Food is considered to be inside the body when it has been absorbed into the bloodstream through the intestinal wall.

Tissue Layers of the Digestive System

• Mucosa
  • Columnar cells: absorb nutrients
  • Goblet cells: secrete mucus
• Submucosa
  • Provides blood supply and nerves to support digestion
• Muscularis
  • Moves food through contractions called peristalsis

Digestion in the Mouth

• First place where digestion occurs.
• Physical digestion: chewing, grinding, tearing caused by the teeth.
• Chemical digestion: release of saliva/enzymes from the salivary glands.

Esophagus and Stomach

• The epiglottis prevents food from entering the trachea.
• After swallowing, the bolus of food travels to the esophagus.
• Physical digestion in the stomach: churning caused by 3 different layers of muscle.
• Chemical digestion: enzymes and acid are secreted.
• Mucus secretion protects the stomach from its own acid.

Chyme and the Small Intestine

• Food is now called chyme as it passes out of the stomach.
• The small intestine is the longest part of the digestive system.
• Lined with small protrusions called villi and microvilli to increase surface area to absorb nutrients more efficiently.

Accessory Organs Aiding Digestion

• Liver: produces bile to digest fats
• Gallbladder: stores and releases bile
• Pancreas: secretes digestive enzymes and bicarbonate
• A lot of enzymes are also added at this stage.

Large Intestine and Elimination

• Remains of the food pass through to the large intestine.
• The appendix has no major digestive role but may help with gut bacteria.
• Most nutrients and water are missing by the time food reaches here.
• More feces due to water absorption.

Physical and Chemical Digestion in the Large Intestine

• Physical digestion: movement of the intestinal muscles.
• Chemical digestion: carried out by bacteria, produces vitamins like vitamin K and gases.

Final Stages of Elimination

• Occur in the rectum, then anus.

Lactose Intolerance and Health Concerns

• Lactose intolerance is caused by a lack of the enzyme lactase, which digests lactose in dairy.
• Two health concerns caused by what we eat: obesity and heart disease.

Suggestions for a Healthy Digestive System

• Eat a balanced diet with fiber.
• Stay hydrated.
• Exercise regularly.