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The Digestive System
• Function- convert foods into
simpler substances that can be
used by cells.
Digestion
Breaking food particles down into simple substances
that cells can used by cells
Mechanical
• Moistening and
breaking food
particles into
smaller pieces
Chemical
• Breaking down chemicals within
food into simpler substances
– Proteins  amino acids
– Fats  lipids
– Carbs
• Polysachararides /starches 
monosacharrides / sugars (glucose)
Digestive Enzymes
• Mouth
• Salivary Amylase- carbs
• Stomach
• Pepsin (proteins)
• Small Intestine (from Pancreas)
• Amylase- carbs
• Trypsin- proteins
• Lipase- fats
• Small Intestine
• Maltase, Sucrase, Lactase- carbs
• Peptidase- proteins
ORGANS OF THE DIGESTIVE SYSTEM
1. Accessory organs: food DOES NOT pass through.
Includes tongue, teeth, salivary glands, liver,
gallbladder, & pancreas
2. Digestive tract: food DOES pass through. Includes
mouth, esophagus, stomach, small & large intestine,
rectum & anus
© 2014 Getting Nerdy, LLC
Mouth
• Mechanical Digestion
– Chewing
– Moistening (saliva)
• Chemical Digestion
– Salivary Amylase
• Enzyme breaks down
carbs
Esophagus
• Epiglottis covers trachea (windpipe) and forces food into
esophagus
• Tube that leads from throat to stomach (lined with
smooth muscle)
– Peristalsis- wavelike muscular contraction that helps
“push” food downward.
Stomache
• Mechanical Digestion- HCl helps “liquefy”
foods and churning motion also breaks
food into smaller pieces
– Food is now chyme
• Chemical Digestion
– Pepsin (breaks down
Proteins)
Liver
• Produces Bile– Bile is a substance that acts as a detergent
and breaks down fat molecules
• Bile is stored in gall bladder and then released into
the small intestine
• Has over 500 other critical
functions
– Mainly breaking down toxins
And “purifying” blood
Gall Bladder
• Stores Bile that is made by liver
– Releases bile Into small intestine
Pancreas
• Produces many digestive enzymes
– These enzymes are released into the small
intestine
– Also produces base
• Alkaline substance
That neutralizes stomach
Acid in small intestines
Small Intestine
• Name refers to diameter, is actually much
longer than large intestine
• 6 meters long
– Almost 20 feet!
• 3 Parts
– Duodenum-chemical digestion
– Jejenum-chemical digestion & nutrient
absorbtion
– Ileum- nutrient absorbtion
Nutrient Absorption in Small Intestine
• takes place in jejenum and ileum
• Chyme is now well digested and rich in nutrients
• Folded surfaces are covered with fingerlike projections called villi
– Villi have are intervened with capillaries from circulatory system
– Nutrients are absorbed into bloodstream
Large Intestine (Colon)
• Water absorption
• Production of vitamin K
– Accomplished by bacterial cells in digestive
tract