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Human digestion _ch[1]._35
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Human digestion _ch[1]._35

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  • 1. Human Digestion -Ch. 35.1 Section Objectives: Interpret the different functions of the digestive system organs. Outline the pathway food follows through the digestive tract. Identify the role of enzymes in chemical digestion .
  • 2. Human Digestion
    • This part of the life process of NUTRITION-> process by which an organism obtains and utilizes food
  • 3. Overview: Food processing occurs in four stages
    • Ingestion : taking in food
    • Digestion : mechanical and chemical breakdown of food so that it can be absorbed by the cells
    • Absorption : cells lining the digestive tract take up (absorb) small nutrient molecules
    • Elimination : undigested material passes out of the digestive tract
  • 4. Human Digestion~ a 2 part process that changes food into a form useable by the body cells
    • 1. Mechanical digestion – physical breakdown of large pieces of food into smaller ones
    • 2. Chemical digestion – hydrolysis – the splitting of large insoluble molecules in small, soluble molecules with the use of water and enzymes ( in other words; breaking complex molecules into simple ones)
    • The process of chemical digestion ( hydrolysis ) is regulated by enzymes
  • 5. Examples of chemical Digestion :
    • 1. Carbohydrates+ water -> simple sugars (glucose for instance)
    • 2. Proteins+ water -> amino acids
    • 3. Lipids+ water -> 3 fatty acids +gylcerol
  • 6. HUMAN DIGESTIVE SYSTEM
    • Human digestive tract = GI ( gastrointestinal ) Consists of a continuous one way food tube ( mouth to anus)
  • 7. HUMAN DIGESTIVE SYSTEM
    • 1 . Mouth : (oral cavity) ingests food
    • 2. Teeth : function in mechanical breakdown of food, increases surface area of food for enzyme action
    • 3. Tongue : acts as a plunger to push food back into the throat ( pharynx ) taste buds are located on the surface of the tongue
  • 8. HUMAN DIGESTIVE SYSTEM
    • Salivary glands are located in the mouth
      • Produce and secrete salivary amylase which starts the chemical digestion of starch
      • Provides lubrication for the chewed food
      • Contains enzymes to kill harmful microbes
  • 9. HUMAN DIGESTIVE SYSTEM
    • 4. Pharynx : food is pushed by tongue to back of throat, initiates swallowing – food is now in the form of a bolus
      • Epiglottis : flap that prevents choking
    • 5 . Esophagus : muscular tube that moves food from mouth to the stomach by process of peristalsis : wave of muscular contractions that moves chewed food to stomach
  • 10. HUMAN DIGESTIVE SYSTEM
    • 6 . Stomach : J-shaped, sac-like , muscular organ that mechanically churns food into a liquid and begins chemical digestion of protein, lining secretes gastric juice, stomach empties in about 2-6hrs., food now liquid called chyme
  • 11. HUMAN DIGESTIVE SYSTEM
    • Components of gastric juice:
      • 1. water-solvent
      • 2. mucus-lubrication
      • 3. pepsin- protease enzyme that begins chemical digestion of protein
      • 4. hydrochloric acid (HCl) ph=2,activates pepsin
  • 12. HUMAN DIGESTIVE SYSTEM
    • 7. Small Intestine : the major organ of chemical digestion and nutrient absorption, long twisted tube with small diameter,
    • enzymes and fluids needed to complete chemical digestion come 3 separate sources:
      • 1. intestine itself
      • 2. pancreas-. Small intestine
      • 3. liver-> gallbladder->small intestine
  • 13. Absorption
    • 7. Small intestine : besides digestion being completed in the small intestine, its other main function is absorption of the digested molecules into the blood
    • Villi : fingerlike projections that increase surface area of small intestine contain a network of capillaries for absorption of amino acids and simple sugars into blood, center contains lymph vessel called lacteal which absorbs fatty acids
  • 14. Accessory organs
    • 1. Pancreas : located near small intestine
      • Produces juices, enzymes, and fluids
      • Produces sodium bicarbonate that neutralizes HCl acid from stomach
      • Works best at neutral pH
  • 15. Accessory organs
    • 2 . Liver : largest internal organ ( has many functions outside digestion)
      • Makes bile ~ bile NOT an enzyme,) bile emulsifies lipids- breaks them into smaller droplets to increase the surface area for enzymes (lipases) to act on fats
    • 3. Gallbladder : small storage sac for bile, carries bile to small intestine
  • 16. HUMAN DIGESTIVE SYSTEM
    • 8 . Large Intestine : primarily a drying and storage organ.
      • undigested and unabsorbed material pass into LI through sphincter muscle
      • No digestion occurs in LI
      • Functions:
        • 1. reabsorption of water and salts
        • 2. absorption of vitamins produced by bacteria that live in the LI
        • 3. storage and elimination of fecal matter
    • 9. Rectum: last part of the digestive system: feces are eliminated through the anus
    Large intestine (colon) Small intestine Rectum Anus End of small intestine Nutrient flow
  • 17. Some Digestive Homeostasis Disorders
    • 1.Constipation – person has uncomfortable or infrequent bowel movements results from sluggish peristalsis that allows excess water to be removed from feces (fecal matter hardens)- may result from insufficient fiber in diet
    • 2 . Diarrhea – opposite of constipation– associated with intestinal disturbances caused by infections or stress– prolonged diarrhea may result in severe dehydration
    • 3. Gall stones – small hard particles made of cholesterol which form & collect in gall bladder- may block the bile duct and cause pain
    • 4. acid reflux -backflow of stomach contents upward into esophagus
    • 5. appendicitis - inflammation of appendix