Digestive System

• What are the main stages of Food Processing?

  1. Ingestion

  2. Digestion

  3. Absorption

  4. Elimination
• Mechanical digestion


  • Starts in the mouth where food is chewed and broken down to smaller pieces for easier digestion
• Chemical digestion


  • Starts in the mouth, carried out by enzymes that speed up chemical reactions
• Amylase


  Enzyme in saliva that helps break down carbohydrates into simpler molecules
• Organs of the digestive system

  • Mouth
  • Pharynx
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus

  
• Accessory organs of the digestive system

  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas

  
• Function of the digestive system

  To help convert large food molecules into simpler molecules (monomers) that can be absorbed and used by the cells of the body
• Mouth


  • Contains teeth, tongue, ducts of salivary glands, palate

  
• Teeth


  • Incisors for biting and cutting
  • Canines for gripping and tearing
  • Premolars for crushing and grinding
  • Molars for chewing

  
• Saliva


  Helps moisten food and makes it easier to chew, begins chemical digestion by breaking down starches
• Lysozyme


  Enzyme in saliva that fights infection by breaking down cell walls of many bacteria
• Esophagus


  Long tube that connects the pharynx with the stomach, uses peristalsis to move food

  
• Bolus


  Chewed clump of food
• Cardiac sphincter


  Thick ring of muscle that closes to prevent stomach contents from moving back up the esophagus

  
• Stomach


  • Large sac of smooth muscle, site of chemical and mechanical digestion
• Chyme


  Mixture of food, digestive juices, and stomach secretions
• Small intestine


  • Enters the duodenum where chemical digestion begins, most absorption of nutrients occurs, contains villi

  
• Large intestine


  • Primary function is to remove water from undigested material, concentrated waste material passes through the rectum and is eliminated
• Rectum


  Warehouse for undigested residue or feces
• Anus


  Exit point for fecal materials
• Digestive system structure, function, and time food/material stays

  • Mouth: Mechanical and chemical digestion, 5-30 seconds
  • Esophagus: Transport, 10 seconds
  • Stomach: Mechanical and chemical digestion, 2-3 hours
  • Small intestine: Mechanical and chemical digestion, 3-4 hours
  • Large intestine: Water absorption, 18-24 hours
  • Colon: Waste storage, 1-2 days

  
• Accessory organs of digestion

  • Salivary glands
  • Liver and gallbladder
  • Pancreas

  
• Salivary glands


  Secrete saliva, a combination of watery fluid and mucus, that lubricates the mouth and contains the enzyme amylase to digest carbohydrates
• Liver


  Produces bile from bilirubin, which emulsifies fats and neutralizes stomach acid
• Gallbladder


  Stores and concentrates bile produced by the liver
• Pancreas


  Contains endocrine cells that secrete hormones and exocrine cells that secrete digestive enzymes directly into the duodenum
• Ingestion 


  act of eating
• Digestion 


  process of breaking food down into molecules small enough to absorb
• Absorption


  uptake of nutrients by body cells
• Elimination


  Occurs as undigested material passes out of the digestive system
• Enzymes


  present in saliva; helps break down carbs into simpler ones that can be used by the body
• Carbohydrates


  large complex molecules