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.