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DIGESTION. The process of preparing your food for absorption

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PowerPoint Slideshow about ' DIGESTION' - rebecca-chen

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The process of preparing your food for absorption


  • To break nutrients into smaller molecules
  • Physical Digestion
  • Mechanical breakdown of food particles
  • Chemical Digestion
  • Enzyme catalyzed breakdown of nutrient molecules
  • Movement of digested nutrients through intestinal wall into:
  • Blood (water soluble nutrients)
  • Lymphatic system - > blood (fat soluble nutrients
digestion the mouth
Digestion:The Mouth
  • Chewing: physically breaks down food into smaller components
  • Food stimulates salivary glands to release saliva
    • Saliva contains amylase-breaks down starch
    • Saliva moistens food for easy swallow
  • Bolus: ball of chewed food mixed with saliva
digestion the pharynx
  • Area responsible for swallowing
  • During swallowing, air passage is blocked by epiglottis
    • Blocks the food from entering the trachea and the lungs
    • Bolus is directed down the esophagus
digestion the esophagus
  • Connects the pharynx and the stomach
  • Bolus is moved towards the stomach by a contractile movement called peristalsis
  • Allows food to move through thoracic cavity, through diaphragm, to peritoneal cavity and the stomach (peristalsis)
digestion the stomach
  • Food passes through a sphincter, (esophageal sphincter) a valve
  • Bolus mixes with stomach secretions to become chyme
  • HCl denatures proteins and kills bacteria
  • Mucus protects stomach wall from acid
  • Chyme released into small intestine through pyloric sphincter
digestion stomach
  • Stops salivary amylase and and slows lingual lipase activity (acid denatures enzyme)
  • Starts protein digestion: pepsin activated and starts protein digestion
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digestion small intestine
  • 20 feet in length
  • divided into three segments:
    • duodenum
    • jejunum
    • ileum
  • 95% of digestion occurs in small intestine
  • Bile: made in liver, stored in gall bladder
    • Emulsifies fats
digestion small intestines
  • Pancreas:
    • Secretes bicarbonate into duodenum to neutralize stomach acid in the chyme
    • Secretes enzymes that act on
      • protein (proteases)
      • carbohydrate (carbohydrases)
      • lipids (lipases)
digestion large intestines
  • Absorbs water and some minerals
  • Supports growth of bacteria that produce Vitamin K
  • Supports growth of other bacteria that partially breaks down fiber
    • We are then able to absorb some of the breakdown products
absorption and transportation
Absorption and Transportation
  • All nutrients must pass through intestinal lining
  • Picked up by capillaries or lymphatic vessels
digestion carbohydrates
  • Begins in the mouth: salivary amylase
    • Amylase denatured in stomach
  • Small intestine: pancreatic enzymes breakdown large CHO’s(starch) to smaller
  • Small intestines: brush border cells produce disaccharidases (sucrase, maltase, lactase)
    • Breakdown sucrose, maltose, lactose
  • Absorption occurs in duodenum & jejunum
digestion protein
  • Protein digestion begins in the stomach
    • Denaturation by HCl
    • Pepsin breaks large proteins into smaller peptides
  • Pancreatic enzymes introduced into the duodenum
    • Break down peptides into amino acids, di- and tri-peptides
    • Intestine enzymes breakdown to amino acids
digestion lipids
  • Mouth: Lingual Lipase, very little activity
  • Stomach: very little activity
  • Small Intestines: Major activity
    • Bile from gall bladder emulsifies
    • Enzymes from pancreas digest and makes the products ready for digestion
      • monoglycerides, glycerol, fatty acids
      • absorbed into cells of microvilli
other systems
Other Systems
  • Cardiovascular
  • Hormonal and Nervous
  • Storage
    • Liver
    • Muscle
    • Fat