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Digestive System
Discuss with your table partner:
What are the different organs in the digestive
tract (pathway through which food travels)?
Give these organs in order.
Mouth ___________  Stomach
________________ _________________
What organs are part of the digestive system
even though they are not part of the digestive
tract, because they produce digestive enzymes
or other substances that are needed for
digestion?
___________________________________________
Discuss with your table partner:
The purpose of the digestive system is to break apart
food polymers into their subunits. (Proteins into amino
acids, Polysaccharides into sugars.)
Mechanical digestion by the teeth does not break apart
these bonds, which requires specific enzymes. But
mechanical digestion plays an important role. How
does grinding food into smaller pieces facilitate
chemical digestion?
Mechanical digestion
__________________,
which allows ____________
______________________
Mouth
• Mechanical digestion
• Chemical digestion of starch
 The salivary glands
produce amylase, an
enzyme that breaks down
____________ .
Esophagus:
Tube that connects mouth to stomach.
Peristalsis:
Involuntary contractions of smooth muscle that _______
____________________________________
Epiglottis: Flap that covers the larynx (upper windpipe)
________________________________ .
Stomach
o Mechanical digestion: muscular churning
o Chemical digestion: Enzyme pepsin digests
______________________________ . Pepsin functional
at low pH (acidic).
Gastric juices (gastric= of the stomach): Contains
_______________________________ in addition to pepsin.
Mucus layer protects stomach from acid.
Video: Movement of Food through the Digestive Tract
Pancreas:
secretes digestive enzymes and hormones.
Trypsin: digests proteins
Lipase: digests lipids
Pancreatic amylase: digests starch
Nucleases: digest nucleic acids
Sodium hydrogen carbonate: creates
alkaline conditions
Video: Digestion of Different Foods
http://www.youtube.com/watch?v=IxNpXO8gGFM
Liver and Gall Bladder
Liver: Produces bile (among many
important functions)
 Bile breaks _____________________.
(mechanical digestion rather than
chemical)
Gall Bladder: Stores bile
Small Intestine
• Small diameter (2.5 cm)
• 6 meters long (provides a large surface)
 Mechanical digestion
 Chemical digestion
________________________ secreted into
duodenum (first section of small intestine)
Discuss with your table partner:
What happens to food after it is digested? What
must be present in the small intestines (where
digestion is completed) for this to occur?
Amino acids, sugars and
fatty acids are __________
_____________________
_____________________
_____________________
_____________________.
Small Intestine Villi
Villi (singular: villus) are small projections in
the small intestine, that _________________
______________________________.
Each villus has a ___________________
and lymph ducts. Digested food is absorbed
for transport.
Lymph vessels
transport fats.
Large Intestine (Colon)
•6.5 cm wide
•1.5 meters long
•Indigestible materials pass into large intestine (such as
cellulose)
• ______________________
•Anaerobic bacteria that reside in colon synthesize
vitamin K and some B vitamins
Review with your table partner:
What are some digestive enzymes and what substrates
do they break down?
Why does the stomach require a mucus lining?
What are two important functions of the small intestine?
What is the main function of the large intestine?