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DIGESTION. The process of preparing your food for absorption

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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