Digestion

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Digestion Nutrition
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Gastrointestinal System (G.I.)

• Structures that ingest, digest absorb food

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Organs of G.I. Tract

• Mouth
• Pharynx
• Esophagus
• Stomach
• Small Intestine
• Large Intestine

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Accessory G. I. Organs

• Tongue
• Teeth
• Salivary glands
• Gastrin glands

• Intestinal glands
• Liver
• Gall bladder
• Pancreas

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Function of G. I. System

• Digestion Chemical Mechanical
• Absorption

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Digestion

• Breakdown of food into smaller molecules that can
  be absorbed by the body

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Mouth

• Mechanical digestion
• Teeth, lips, cheek, tongue
• Chemical digestion
• Saliva salivary amylase
• Initiates carbohydrate breakdown

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Salivary Glands

• Produce saliva
• 3 glands
• Parotid
• Sublingual
• Submandibular

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Saliva

• Mixture of water, mucus, salivary amylase
• 3 functions of saliva

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Saliva Function 1

• Dissolves food combines with mucus to speed up
  digestion
• Lubricates food into a ball bolus

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Saliva Function 2

• Contains enzymes that attack microorganisms that
  can enter mouth

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Saliva Function 3

• Contains enzymes salivary amylase which
  breakdowns starch

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Pharynx

• GI tract respiratory tract cross
• Passageway that moves food from mouth to esophagus

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Esophagus

• Tube which connects pharynx with stomach
• Peristalsis moves bolus down esophagus
• No digestion
• Sphincter acts like valve

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Stomach

• Muscular sac
• Glands in lining secrete gastric juices
• Ex. Parietal cells
• Ex. Chief cells
• Chemical mechanical digestion
• Protein digestion

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Stomach Glands

• Secrete mucus lubricates food
• Produces mucin protects lining of stomach from
  acid
• Parietal cells secrete HCl
• Chief cells secrete pepsinogen
• HCl pepsinogen pepsin
• Pepsin enzyme that chemically digest proteins

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Stomach cont.

• Walls of stomach contract mixing food with
  gastric juices
• Produces chymepast mixture
• Pyloric valve opens and chyme moves to S.I.

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Small Intestine

• Chemical digestion
• Absorption
• 3 regions
• Duodenum
• Jejunum
• Ileum

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Small Intestine

• Duodenum chemical digestion
• Jejunum ileum most digestion completed at this
  pointMost absorption
• Walls folded have villi (contain many blood
  vessels)

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Small Intestine

• Enzymes digestive fluids continue to break down
  chyme
• Source of enzymes small intestine, pancreas,
  liver

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Small Intestine Enzymes

• Pepsidase protein digestion
• Maltase maltose
• Lactase lactose
• Sucrase sucrose

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Large Intestine

• Removes water from undigested waste
• Feces undigested waste
• Collect at rectum (end of colon)

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Liver

• Produces secretes bile

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Gall Bladder

• Stores bile
• Concentrates biles

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Bile

• Mixture of cholesterol, colored pigments, bile
  salts
• Emulsifies fats

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Pancreas

• Secretes pancreatic fluid
• Pancreatic fluid enzymes in fluid break down
  carbohydrates, fats, proteins

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Pancreatic secretions

• Enzymes
• Amylase carbohydrates
• Proteases proteins
• Lipase lipids (fats)
• Sodium Bicarbonate neutralizes HCl