Digestive System — Science 8 Q4

• Digestive System


  Breaks down large compounds in food and liquids into smaller molecules that can be absorbed into the bloodstream. These are processed, then delivered throughout the body and used for energy, growth, and cell repair.
• Divisions of the Digestive System

  • Mouth Cavity
  • Pharynx
  • Esophagus
  • Stomach
  • Small Intestine
  • Pancreas
  • Liver
  • Gallbladder
  • Large Intestine / Colon
• Mouth Cavity


  • Serves as entrance of food
  • Teeth cut and chew the food into smaller pieces
  • Tongue manipulates the food for better chewing
  • Salivary Glands secrete saliva, help form a food bolus, contain salivary amylase and lipase
• Pharynx


  • Serves as a passageway for air and food
  • Funnel-shaped end of the mouth cavity that leads to the esophagus
• Esophagus


  • Moist muscular tube that connects the pharynx to the stomach
  • Delivers food to the stomach through rhythmic contractions called peristalsis
• Stomach


  • Saclike and the most expanded part of the food tube
  • Its walls contain gastric glands that secrete hydrochloric acid and pepsin for preliminary digestion
  • Cardiac Sphincter relaxes to allow food into the stomach
  • Pyloric Sphincter remains closed during digestion
• Small Intestine


  • Has walls covered with intestinal villi
  • Source of enzymes that are mixed with chyme
• Pancreas


  • Produces pancreatic juice with alkaline fluid and enzymes to break down sugars, fats, and starches
• Liver


  • Largest gland in the body
  • Produces bile to break down fats
  • Stores fat, glycogen, iron, and certain minerals, and detoxifies certain chemicals
• Gallbladder


  • Stores bile from the liver
  • Bile is secreted into the duodenum in the presence of fatty food
• Large Intestine / Colon


  • Absorbs water
  • Eliminates indigestible food from the body as feces
  • Does not participate in digestion of food
  • Rectum is a short tube at the end
  • Anus is the lower opening of the food tube and is a muscle
• Digestive Processes


  1. Ingestion - Taking food into the digestive system

  2. Digestion - Breakdown of food chemically and mechanically

  3. Absorption - Nutrients pass through cell membranes

  4. Assimilation - Making food part of cell and utilizing nutrients

  5. Excretion / Defecation - Removal of indigestible/undigested substances and wastes
• Gastrointestinal Tract / Alimentary Canal (GI)


  • A series of hollow organs joined in a long, twisting tube from the mouth to the anus
  • Ingestion - Taking food into the digestive tract
  • Propulsion - Swallowing and peristalsis
  • Mechanical Digestion - Chewing, mixing, and churning food
  • Chemical Digestion - Catabolic breakdown of food
  • Absorption - Movement of nutrients from the GI tract to the blood or lymph
  • Defecation - Elimination of indigestible and unabsorbed solid wastes