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Digestion
+Video: Magic School Bus
http://www.youtube.com/watch?v=oewpZ3ttOF8
+
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
+
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)
+
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
+
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
+
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
+
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)
+
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 →
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