s

• Digestion


  The process of breaking down large, insoluble food molecules into smaller, soluble ones that can be absorbed into the bloodstream
• Digestion process


  1. Ingestion

  2. Absorption

  3. Assimilation

  4. Ejection
• Ingestion


  • The intake of food into the digestive system, involving physical and chemical digestion in the mouth
• Absorption


  • The process where the small, soluble food molecules pass across the intestinal wall and into the bloodstream
• Assimilation


  • The process where the absorbed nutrients are delivered to the body's cells and incorporated into complex substances like proteins
• Ejection


  • The removal of undigested food and waste products from the body through the anus
• Organs of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Liver
  • Gallbladder
  • Pancreas
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
• Mouth


  • Physical and chemical digestion of food takes place here
• Esophagus


  • Muscular tube that transports food from the mouth to the stomach
• Stomach


  • Mixes and grinds food, begins chemical digestion with acids and enzymes
• Small intestine


  • Completes digestion and absorption of nutrients into the bloodstream
• Large intestine (colon)


  • Absorbs water from undigested food, forms and expels feces
• Rectum


  • Stores feces until it can be expelled through the anus
• Anus


  • External opening where feces are expelled from the body
• Liver


  • Produces bile to aid in fat digestion, helps cleanse blood of toxins
• Gallbladder


  • Stores and concentrates bile produced by the liver
• Pancreas


  • Produces enzymes that help break down fats, proteins, and carbohydrates
• The digestive system is approximately 9 meters long
• It takes about 36 hours for food to pass through the colon
• Plants give us oxygen


  We use the oxygen and release carbon dioxide, which is essential for plant growth
• Digestion involves both physical (mechanical) and chemical processes
• The purpose of digestion is to break down large, insoluble food molecules into smaller, soluble ones that can be absorbed into the bloodstream
• Nutrition


  Process by which organisms obtain and utilize their food
• Holozoic nutrition


  • Mode of feeding found in animals
  • Involves the ingestion of liquid or solid organic material, digestion, absorption and assimilation of it to utilize it
  • Includes taking in the complex substances and converting them into simpler forms
• Nutrition process


  1. Ingestion - taking food into the digestive system

  2. Digestion - breakdown of food (either chemically or mechanically) in order to utilize nutrients

  3. Absorption - process in which digested food materials are absorbed by the body cells

  4. Assimilation - transport and use of absorbed nutrients by the cells such as the food's conversion into new protoplasm to provide energy

  5. Elimination - passing of undigested material out of the digestive tract

  
• Types of Nutrients


  • Micronutrients - vitamins, minerals, & water
  • Macronutrients - proteins, lipids, carbohydrates, etc...
• GI (gastrointestinal) tract


  Alimentary canal
• Mouth


  • Mechanical digestion - breaking up food
  • Chemical digestion - digest starch
  • Kill bacteria
  • Moisten food

  
• Chewing


  Mechanical/physical digestion
• Saliva breaking down saltine

  Chemical digestion
• Tongue breaking apart hamburger

  Mechanical/physical digestion
• Pepsin breaking down hamburger

  Chemical digestion
• Pharynx


  • Back of the throat
  • Larynx - passage for air, closes when we swallow
  • Approximately 15cm long

  
• Swallowing


  1. Epiglottis - flap of cartilage that closes trachea (windpipe) when swallowing, food travels down esophagus

  2. Peristalsis - involuntary muscle contractions to move food along

  
• Digestive Glands


  Groups of specialized secretory cells found in the lining of the alimentary canal or accessory organs

  
• Stomach


  • Food is temporarily stored here
  • Gastric juices are secreted
  • Has layers of muscle that line the inside
  • Mechanically and chemically breaks down food
• The stomach is made out of protein, but it doesn't digest itself because mucus secreted by stomach cells protects the stomach lining
• Stomach functions


  • Food storage - can stretch to fit ~2L food
  • Disinfect food - HCl = pH 2 kills bacteria
  • Chemical digestion - pepsin enzyme breaks down proteins

  
• Gastric Juices


  • Secreted by the stomach
  • Acidic (pH 1.5-2.5) (HCl)
  • Pepsin - an enzyme that breaks down large proteins into amino acids
  • Food is further broken down into a thin liquid called chyme
• Accessory Organs


  • Pancreas
  • Gall Bladder
  • Spleen