DIGESTION

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DIGESTION

• The process of preparing your food for absorption
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What Happens to the Food We Eat?
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Digestion

• To break nutrients into smaller molecules
• Physical Digestion
• Mechanical breakdown of food particles
• Chemical Digestion
• Enzyme catalyzed breakdown of nutrient molecules

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Absorption

• Movement of digested nutrients through intestinal
  wall into
• Blood (water soluble nutrients)
• Lymphatic system - gt blood (fat soluble nutrients

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DigestionThe 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

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DIGESTIONTHE 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

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DIGESTIONTHE 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)

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Digestion Chewing
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Digestion Swallowing
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Digestion Swallowing
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DIGESTIONTHE 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

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DIGESTIONSTOMACH

• 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 The Stomach
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DIGESTIONSMALL 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

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Digestion Accessory Organs
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Absorption
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DIGESTIONSMALL INTESTINES

• Pancreas
• Secretes bicarbonate into duodenum to neutralize
  stomach acid in the chyme
• Secretes enzymes that act on
• protein (proteases)
• carbohydrate (carbohydrases)
• lipids (lipases)

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DIGESTIONLARGE 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

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Absorption and Transportation

• All nutrients must pass through intestinal lining
• Picked up by capillaries or lymphatic vessels

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DIGESTIONCARBOHYDRATES

• Begins in the mouth salivary amylase
• Amylase denatured in stomach
• Small intestine pancreatic enzymes breakdown
  large CHOs(starch) to smaller
• Small intestines brush border cells produce
  disaccharidases (sucrase, maltase, lactase)
• Breakdown sucrose, maltose, lactose
• Absorption occurs in duodenum jejunum

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DIGESTIONPROTEIN

• 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

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DIGESTIONLIPIDS

• 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

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Other Systems

• Cardiovascular
• Hormonal and Nervous
• Storage
• Liver
• Muscle
• Fat