REVIEWER IN SCIENCE

• Digestive system

  • Responsible for breaking down food into nutrients that our body can absorb and use for energy, growth, and repair
  • Plays a crucial role in removing waste and toxins from our bodies
• Digestion

  1. Ingestion

  2. Absorption

  3. Assimilation

  4. Excretion
• Ingestion


  • The process of taking in food into the mouth
  • Eating
• Absorption

  • Movement of nutrients in the blood stream
  • Occurs in the small intestine
• Chyme

  A thick slurry semifluid substance that enters the intestine from the stomach
• Assimilation

  Nutrients are transported to the liver where they are processed and either stored or released into the bloodstream for use by the body's cells
• Excretion

  • Starts in the large intestine, where water is absorbed, and the waste is formed into feces
  • Waste and toxins are excreted through the rectum and anus
• Types of digestion

  • Mechanical (physical) digestion
  • Chemical digestion
• Mechanical (physical) digestion

  • Chewing, tearing, grinding, mashing and mixing of food
  • Happens in the mouth
• Chemical digestion

  Enzymatic reactions to improve digestion of carbohydrates (glucose), proteins (amino acids), and lipids (fats and oils)
• 4 Main Components of the Digestive System


  • Gastrointestinal tract
  • Pancreas, liver and gall bladder
  • Enzymes, hormones, nerves and blood
  • Messentary
• Gastrointestinal tract

  Composed of mouth, esophagus, stomach, small intestine, large intestine, rectum and anus
• Messentary

  A large stretch of tissue that supports and positions all digestive organs in the abdomen
• Structures of the Digestive System


  • Mouth
  • Esophagus
  • Stomach
  • Small Intestine
• Mouth


  • Teeth mechanically break down food into small pieces
  • Food will be mixed with saliva turning into a moist lump called bolus
  • The enzyme in the saliva called salivary amylase helps break down starch
• Esophagus


  • Approximately 20-25 cm long
  • A passageway that Moves food from the throat to the stomach using muscle movement called Peristalsis
  • The Epiglottis covers the pharynx during swallowing so that food does not enter the lungs
• Stomach


  • J-shaped muscular bag that stores the food you eat, breaks it down into tiny pieces
  • The stomach muscles contract and churn the food, thoroughly mixing it with the digestive juices resulting in the formation of a semi-liquid substance called chyme
• Small Intestine


  • Measures roughly 6.7 –7.6 meters long
  • It serves as the area of absorption due to its surface with the presence of villi and microvilli on the inner lining
  • Villi are tiny finger-like projections which greatly increase the surface area available for nutrient absorption
  • Nutrients from the food pass into the bloodstream through the small intestine walls
  • Completes the process of digestion