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Digestion

+Video: Magic School Bus

http://www.youtube.com/watch?v=oewpZ3ttOF8

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The Masher

Drag picture to placeholder or click icon to add

Drag picture to placeholder or click icon to addMouth

+Mouth

Seeing or smelling food can start saliva flowing in mouth saliva starts to break down food chemically & adds water Carbs can be broken

down into simple sugars by maltase and amylase (enzymes)

Chewing and grinding teeth can physically break down food (mastication)

Tongue pushes food to back of mouth where epiglottis is located Epiglottis closes trachea

(tube to lungs), stopping food from going down trachea and instead forcing food down the esophagus

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The Passage

Drag picture to placeholder or click icon to add

Drag picture to placeholder or click icon to addEsophagu

s

+Esophagus

Tube-like passage carries food from the mouth to the stomach

Coated with a membrane lining that secretes mucus (protect against acid, foods not thoroughly chewed, etc.)

Food broken down into smaller particles through the esophagus by peristalsis (waves of muscular contractions)

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The Churner

Drag picture to placeholder or click icon to add

Drag picture to placeholder or click icon to addStomach

+Stomach

Grind and churns food and mixes it with acid and enzymes (forming chyme)

Comfortable capacity is 1-2 L, can stretch 3-4 L

Cells lining the stomach secrete gastric juice that contains: Mucus – Protects stomach from

enzymes and acid Hydrochloric acid – Creates a

high acid environment which aids helps pepsin and prevents harmful bacterial growth Pepsin is the only enzyme

that can break down collagen (a protein and major component of meat)

Enzymes – Begin digestion of protein and fat (ex. pepsin, gastric lipase)

Gastrin – Hormone made by body and controls acid secretion

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The Absorber

Drag picture to placeholder or click icon to add

Drag picture to placeholder or click icon to addSmall

intestine

+Small intestines

Has three sections: duodenum, jejunum and ilium

Duodenum is the first part of small intestines, receives enzymes from pancreas and bile from liver to continue digestion Enzymes are necessary to

break down carbs and protein

Most absorption happen in the jejunum and ilium: lining is specially designed to create the greatest possible surface area for nutrient absorption

By end of small intestines, mostly water, dissolved minerals and indigestible fibre remain

All nutrients that are absorbed through the small intestines are filtered through the liver

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The Poop Maker

Large intestine

+Large intestine

Includes cecum, appendix, colon and rectum

Food (chyme) passes through large intestine by peristalsis

Body absorbs water and vitamins (some bacteria in the colon actually produce vitamins)

+Important organs that are not a part of the digestive tract

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The Filter

Liver

+Liver

Nutrients that are absorbed through the intestinal walls enter veins and are filtered through the liver Removes bacteria and

foreign particles

Manufactures half of the body’s cholesterol Cholesterol is then used

to create bile (a greenish liquid that helps the body digest and absorb fat)

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The Producer

Drag picture to placeholder or click icon to add

Drag picture to placeholder or click icon to addPancreas

+Pancreas

Produces digestive enzymes and hormones Digestive enzymes are

released into the duodenum (small intestines) and hormones into the bloodstream

Insulin is a hormone produced by the pancreas Insulin reduces blood

sugar by moving sugar (glucose) into cells

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The Holding Tank

Drag picture to placeholder or click icon to add

Drag picture to placeholder or click icon to addGallbladd

er

+Gallbladder

Stores bile

When food enters into the duodenum, it signals to the gallbladder to release bile

Bile: Helps to breakdown

cholesterol, fats, fat-soluble vitamins

Drugs and other waste products are excreted in bile

Bile salts are absorbed at the end of the small intestines and recirculate

+Video: What causes constipation?

http://www.youtube.com/watch?v=cdijh32NiLs

+Video: How digestion works

http://www.youtube.com/watch?v=eTMzl1cblZc

+Video: Why do I have gas?

http://www.youtube.com/watch?v=IfuyaMYapkY

+How long does it take to process a complete meal?

24 hours 4 hours in stomach6 hours in small intestineremaining 14 hours in large intestine

+Nutrient Digestion

Nutrient Mouth Stomach Small Intestine Large Intestine

Water ← Added → ← Reabsorbed →

Carbohydrates ← Breakdown by enzymes → ←Most absorbed→ ← Remaining broken Down by bacteria→

Proteins ← Breakdown by enzymes → ←Most absorbed→

 

Fats   ← Breakdown by enyzmes → ←Emulsified by bile→ ←Most absorbed→

Vitamins     ←Most absorbed→

Minerals   ←Most absorbed→←Some salts absorbed with water→

Dietary Fibre(non-nutritive

  ← Collected for excretion →