Digestive System:
pp. 900-911
• Pre-Movie:
http://kidshealth.org/kid
/closet/movies/how_the_
body_works_interim.html
• Major structures:
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Mouth
Throat
Esophagus
Stomach
Liver
Pancreas
Small and large intestines
http://www.encognitive.com/images/digestive-system-2.jpg
Digestive System Key Functions
• Extracts and absorbs nutrients from food
• Removes wastes
• Maintains water and chemical balances
Key terms
• Nutrient – a substance required by the body for energy,
growth, repair, and maintenance. Nutrients in food and
beverages include:
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Carbohydrates
Lipids
Proteins
Vitamins
Minerals
• Digestion – the process of breaking down food into
molecules the body can use
• calorie – a unit by which the energy available in food is
measured
• It is the amount of heat energy required to raise the temperature of 1g
of water 1oC
• A calorie is actually a very small amount of energy so nutritionists use a
unit called the Calorie (with a capital C) which is equal 1,000 calories
http://static.howstuffworks.com/gif/calorie.gif
Terms Cont’d
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Carbohydrates – sugars
Proteins – amino acids
Lipids – fats
Vitamins – organic substances that occur in many foods in
small amounts and are necessary in trace amounts for the
normal metabolic functioning of the body (e.x. fat-soluble
vitamins – A, D, E, K; water-soluble vitamins – C and B)
• Minerals – naturally occurring inorganic substances that are
used to make certain body structures and substances, for
normal nerve and muscle function, and to maintain osmotic
balance. Your body doesn’t produce them, rather you need
to intake them.
• Teeth and bones require calcium and phosphorus
• Iron is needed for the transportation of oxygen
• Magnesium, calcium, sodium, potassium, and zinc help regulate
function of the nerves and muscles
From Mouth to Anus
• Food travels more than 26
feet through your digestive
tract, which consists of the
mouth, pharynx, esophagus,
stomach, small intestine,
large intestine, and rectum
• The liver and pancreas are
not part of the tract, but they
deliver secretions into the
tract through tubes called
ducts
http://www.surgery.uthscsa.edu/surgicaloncology/pancreas.jpg
Pathway Cont’d
• In your mouth, teeth rip and chew
food. Also, saliva contains enzymes
(amylases) that begin to help
breakdown carbohydrates
• Esophagus connects the mouth to
the stomach through a valve called a
sphincter
– Stomach is just beneath the
diaphragm
• Stomach: temporarily stores food
and also breaks it down
– Gastric juice is secreted by the cells
that line the inside of the stomach,
and it is made up of hydrochloric acid
and pepsin
http://graphics8.nytimes.com/images/2007/08/01/health/adam/8756.jpg
Pathway Cont’d
• Food passes from the stomach
into the small intestine with a
sphincter
– Digestion and absorption of
nutrients
• The first part of the small
intestine (duodenum) receives
secretions from the pancreas,
liver, and gallbladder
• Liver produces bile (helps
break down fats) which is
stored in the gallbladder and
released to the small intestine
• Most absorption, or passage of
nutrients to the blood or
lymph, occurs in the small
intestine
Pathway Cont’d
• Food wastes move into the large
intestine (colon); no digestion
takes place here
– Mostly mineral ions and water
are absorbed through the wall
of the large intestine
• Bacteria in your colon help make
compounds your body needs
(ex. vitamin K and several B
vitamins) but also help
transform and compact the
undigested materials into feces
• The final segment of the large
intestine is called the rectum
and from the rectum the solid
feces are eliminated from the
body through the anus
http://pennstatehershey.org/healthinfo/graphics/images/en/10255.jpg
http://curezone.com/upload/_N_Forums/Natural_Heali/f26_1_digestive_system_c.jpg
Diarrhea
• When wastes are rushed through the large
intestine before the remaining water is
absorbed = watery feces
http://tell.fll.purdue.edu/JapanProj/FLClipart/Medical/diarrhea.gif
Constipation (hard feces)
• When food remains in the colon for long
periods of time, which causes much water to
be absorbed
http://www.dollymix.tv/parent_constipation1.gif
More about your liver
• Open and read “The Liver’s Role in Digestion”
and “The Liver’s Role in Metabolism” on pages
910-911
Modeling the Function of Bile
• Quick Lab Activity, p. 911 DEMO
Digestive System Practice
• Do all three activities at
http://www.harcourtschool.com/activity/digest/index.
htm
– Building Your System
– Inside Story
– Food Path
• http://msjensen.cehd.umn.edu/Webanatomy/timed/3
1.htm
• http://www.ugoplayer.com/games/digestivesystem.ht
ml
• http://nature.ca/discover/exm/blddgstvsystm/index_e.
cfm