Digestive System

• Incomplete digestive system


  Organisms with one opening on their digestive tract
• Complete digestive system


  Organisms with two openings on their digestive tract, like humans and some animals
• Digestion


  Breaking down food into absorbable forms
• Mechanical digestion


  The physical breaking down of food into smaller pieces
• Chemical digestion


  Using enzymes and acids to break down food
• Processes of digestion


  • Ingestion
  • Absorption
  • Assimilation
  • Elimination
• The primary functions of the digestive system are the breakdown of food (digestion) and absorption of nutrients
• Digestion in the mouth


  1. Food broken into smaller particles by teeth during mastication

  2. Saliva from salivary glands begins chemical digestion and keeps food moist

  3. Soft palate locks upper pharynx to prevent food entering nasal cavity

  4. Muscles in face, neck and tongue contract to push food through pharynx

  5. Food passes over epiglottis to prevent entry into respiratory system

  6. Food enters esophagus
• Digestion in the stomach

  1. Food mass (bolus) enters stomach

  2. Stomach cells secrete hydrochloric acid and enzymes to chemically digest bolus

  3. Muscular contractions further break down and mix bolus with stomach secretions to form chyme

  4. Chyme exits stomach through pyloric sphincter into small intestine
• Digestion in the small intestine

  1. Chyme enters small intestine (duodenum, jejunum, ilium)

  2. Bile from liver and digestive enzymes from pancreas aid digestion

  3. Nutrients absorbed from lumen of small intestine into blood

  4. Unabsorbed chyme enters large intestine
• Digestion in the large intestine

  1. Water and salt absorbed from chyme

  2. Chyme converted into feces

  3. Feces stored in rectum until elimination through anus
• Absorption of nutrients


  The process of absorbing nutrients from broken-down food into the bloodstream, allowing them to be transported to cells throughout the body.
• Breakdown of food (digestion)


  The process of breaking down food into smaller molecules using mechanical and chemical methods, such as chewing and enzymes.